Air, Fuel, Motors, and missives. Article. (Updated 1/3/06)

[Tapper]

This is long, so be prepared. Hopefully, its worth the effort. The object here, is to give our readers a good baseline of information about how their VTX's work, and address some of the most common questions produced on this forum in a thoughtful and complete way.

Having read hundreds of posts on these topics, I decided to take a stab at writing something to clarify the many misconceptions on this subject. Whether it’s interminable questions about backfiring/popping, or arguments about “load”, or discussion about whether aftermarket fuel computers are necessary and which is best, we see a lot of bad information and mistaken ideas being tossed around as fact. So lets take a look at the basics, and then talk about a few specifics.

Pressure is the thing

The single most important thing to understand about an internal combustion engine is that at its very root, itÂ’s nothing but an air pump. If you can get your mind around that one simple concept, understanding everything else is a lot simpler and more straightforward.

Ever consider your own lungs? As it happens, your body is also a pretty efficient air pump. When you take a breath, your diaphragm muscle contracts and pulls your lungs downwards in your chest, and this increases their size by stretching them. This increase in volume causes a decrease in pressure (applies vacuum) to your windpipe, and this causes air to rush into your chest. Air always flows from an area of high pressure to an area of low pressure. How fast it flows, depends on the difference in pressure. The bigger the difference, the faster air moves. The bigger the volume, the more air needs to move to equalize the pressure. When you exhale, the reverse happens – your diaphragm relaxes, causing the volume in your lungs to decrease, which increases the pressure inside your lungs, which makes air flow out of your windpipe – to the outside air, which is now at a lower pressure than your lungs.

The pressure is the thing. Differences in pressure make the air move. All around you, at this very minute, is a bunch of air that stretches up above you for several miles. The weight of all that air, presses down on the air below it, and causes the air that surrounds you to be under pressure. This is called “atmospheric pressure”. It is the baseline around which we talk about the pumping of air. You should understand something else here, the concept of “vacuum”. Vacuum, at least with respect to motors, just means “lower pressure than atmospheric”. If you create a vacuum, what you are really doing, is creating an area where the air pressure is lower than the surrounding atmospheric pressure. If you give it a way to do so, air is going to try real hard to kill that vacuum by sending air into it. Nature abhors a vacuum. Air always moves from an area of high pressure to an area of low pressure, and the amount of force it does so with is proportional to the difference between the two pressures. Sounds simple, no? It really is, but it also confuses folks.

Remember I said a motor was just a big air pump? It is, and it works exactly the same way your lungs do. On the intake stroke, as a piston travels down its cylinder, the area in the cylinder increases rapidly – and causes a vacuum. When the intake valve opens, air rushes into the cylinder, and causes a drop in pressure in the intake manifold that is proportional to the amount air moving into the cylinder. On the exhaust stroke, the burning fuel and air has created very high pressure in the cylinder, and when the exhaust valve opens, the pressure in the exhaust header is much lower than the cylinder, so the gas rushes out into the exhaust pipe.

If this sounds simple or obvious to you, then great. But make sure you really do understand these concepts, because understanding the way a motor works means understanding the sequence of pressure changes. If you donÂ’t understand, then none of the rest of this is going to gel for you.

Different Strokes Move the World, Willis.

Ok, now its time to see what the air pump really does, and what drives it, and that means understanding strokes. For the purposes of this article, weÂ’ll focus on a 4-stroke motor, since our bikes use them, and since the vast majority of motors are 4-strokes.

http://www.vtxoa.com/engine_running.gif

Lets simplify, and look at each stroke.

Intake stroke – This is the first stroke in our series of four. In this one, the piston is moving downward in the cylinder with the intake valve open, causing a vacuum to be created in the cylinder and more importantly, in the intake manifold where the carburetor or fuel injectors live. The vacuum (area of low pressure) created in the intake manifold is the power that drives the fuel system, and gets the fuel into the cylinder where we want it. The larger the vacuum (lower the pressure), the more fuel is pumped into the cylinder. The faster the piston moves downward in the cylinder, the bigger and faster the vacuum is created, and the more fuel gets pumped. Therefore, it also follows, that the higher the engine’s RPM, and the harder an engine is working, the higher the vacuum (or lower the pressure) exists in the intake manifold.

At this moment, I hope your brain is saying to you “whoa – that vacuum measurement is sure an important number to know if I’m going to know what my motor is doing”. Damn skippy it is – so lets define something important right now:

The amount of vacuum produced by a motor is a direct measurement of the load placed on the motor. Therefore, when discussing motors, Load means the amount of air being demanded by a motor, which is equivalent to the amount of vacuum developed in the intake manifold, which is the same as the pressure difference inside the manifold and the outside air.

Woo! Now we understand the mysterious load. ItÂ’s a great number to know, and is used by fuel injection computers to determine how much fuel to squirt into the intake manifold. ItÂ’s also the energy that makes a carb shoot a given amount of fuel out of its jets. WeÂ’ll talk about carbs and fuel injection a little later, so lets move on with the strokes.

Compression Stroke – Ok, the piston has moved as far down in the cylinder as it possibly can on the intake stroke (called bottom dead center or BDC), and starts its way back upward. The intake valve closes and so we have a volume of air and fuel trapped in the cylinder, and suddenly the space it occupies is gonna get squished real hard (compressed), as the piston begins moving upward in the cylinder. This causes the pressure in the cylinder to increase very rapidly, since the charge has nowhere to go. One thing to remember here – fuel burns much faster under pressure.

Power Stroke – Ok, all the valves are closed, we’ve got our air/fuel charge compressed really tight, and put it under a lot of pressure as the piston gets to the very tippity top of it’s path through the cylinder (called Top Dead Center). At this point we set the charge on fire, and as it burns it produces a whole bunch of gas, which rapidly increases the pressure in the small space, and pushes the cylinder downward very hard. This is where all the power in your motor comes from, this rapidly expanding gas pressure. A couple of things to note here.

First, we ignite the mix using the spark plug. If the plug were to fire at exactly top dead center (TDC), we could arbitrarily call that the zero position of the crankshaft, and indeed, that’s exactly what we do. Remember, the crankshaft is rotating in a circle throughout this process. One rotation of the crankshaft (360 degrees) means one complete up and down motion of the piston. When we talk about “timing” in a motor, what we’re really talking about is the relationship of the spark to the moment of TDC or the zero position of the crankshaft. If we fire the spark plug before TDC (BDTC, or during the end of the compression stroke), we call that advancing the spark. If we fire the plug after (ATDC, or during the power stroke), we call that retarding the spark.

Exhaust Stroke – Ok, the piston is now hauling ass downwards, and the cylinder is full of hot and probably still burning gas and residual fuel/air. As the piston crosses bottom dead center (BDC) again and starts upward, we enter the exhaust stroke. During the stroke, the exhaust valve opens, and since the cylinder is now at a much higher pressure than the exhaust pipe, all that hot gas and stuff goes flying into the exhaust header, and out the pipe. That’s the end of the 4 strokes, and when the piston crosses TDC again, the whole process starts anew, and away we go.

A couple of things to note here. YouÂ’ll notice, that during all four strokes, the crankshaft rotates two full rotations, and travels through 720 full degrees. The camshafts, which actuate the valves, have traveled through one full rotation, or 360 degrees. You often see guys tossing around degree measurements when discussing things like spark timing, cam timing, cam profiles, and so forth. So itÂ’s important to be able to relate the concept of degrees, to the actual rotation of the parts. If you were really good at math in school, youÂ’ll immediately notice that any given instant in the cycling of a motor can be described using simple trigonometry, which should give you some pretty important insights into the ways fuel injection computers and electronics work on your motors. But thatÂ’s a bit lofty a subject for this article, so lets move along, shall we?

It Gives me Gas

Well, now that weÂ’ve got the strokes, let talk about gas, and the fuel system in general. IÂ’m going to focus on describing a fuel injection system, because once you understand that, understanding a carbureted system is vastly easier.

So. We know that load (or vacuum demand) is the way fuel is delivered to the cylinder, but how does the motor know how much fuel? And how much fuel is actually needed?

Lets start, by talking about the air/fuel ratio.

A ratio, just means “amount of one thing compared to amount of another”. In our case, it means amount of air compared to the amount of fuel. When you see someone talk about air/fuel ratios, they usually put the air part first, followed (or divided) by the fuel part. So an A/F ratio of 13 to 1, or 13-1, or 13/1 just means “thirteen parts air to one part fuel”.

Now, lets talk a little simple chemistry. The burning of air and fuel is just a chemical reaction called combustion. Chemical reactions are described by chemists in chemical equations, and the science of balancing these equations, or determining how much of each chemical reacts, is called “stoichiometry”. Lets look at a simple one:

1O2 + 2H2 --> 2H2O

It’s a little hard to read that, but it just means “One molecule (consisting of two atoms) of Oxygen plus two molecules (consisting of two atoms each) of Hydrogen will react and form 2 molecules of water”. You’ll notice, that in this reaction, everything gets used up, and no atoms are left over, and so the reaction is said to be “stoichiometric” (i.e. nothing is left over), and now you know where that big word comes from that gets tossed around when people talk about A/F ratios. It just means “completely burnt with nothing left over”. Glad we got that out of the way.

Now that we understand stoichiometric A/F ratios, lets define a couple of things.

An A/F ratio is said to be “Lean”, when there is air left over after burning.

An A/F ratio is said to be “Rich”, when there is gasoline left over after burning.

Now, the perfect stoichiometric A/F ratio varies based on a lot of factors, like the formulation of the gasoline, or the density of the air, but in general, we can say itÂ’s in the neighborhood of 14.7 parts of air to one part of gas, or 14.7/1 (the VTX really likes 13/1 to make best power).

So now we understand ratios, and what ratio we are aiming at, but how does the motor get the right amount of gas in to make that ratio? Vacuum, thatÂ’s how.

A carbureted motor does it directly, by varying the size of its jets. The carb sits in-line between the outside air pressure (air filter) and the manifold pressure (load or vacuum). The action of the air flowing through it into the manifold causes suction in the jets, which pull gas out of the bowl, and spit it into the intake manifold. The bigger the jet, the more gas gets spit out for a given vacuum. But itÂ’s a little different in a fuel-injected motor, since the fuel injectors are turned off and on by the computer (ECU). So how does the computer measure the load to know how long to turn the injectors on? By using sensors.

There are several involved in this process, with the most important being the “MAP” (manifold absolute pressure) sensor, which directly measures the pressure in the intake manifold. The computer then compares this pressure to the outside air pressure, or barometric pressure (obtained by reading the BAR sensor), and now knows just how much vacuum the motor is pulling. In order to get load though, the computer needs to know how much air is being pulled into the cylinders, so it needs to know the air density as well. It does this by looking at the intake air temperature measure by the “IAT” sensor. The ECU has a table of density values in it that compares density at various temperatures and pressures. It just takes the values it read from its IAT and (adjusted) MAP sensor, looks up the density value for these readings in its table, and “hey presto”, your ECU now has a direct measurement of the load on your motor. Now that the ECU knows the load, it just has to figure out how long to turn the injectors on to get the right A/F ratio (which it does by looking it up in a fuel table by comparing load to RPM), and boom – we got gas. The same table is also used to look up the right time to fire the spark plugs (timing). Honda calls this “three dimensional fuel programming”, and I guess that’s sort of accurate.

There are other sensors that play less important roles in the process, like O2 sensors on California bikes, WTS (water temperature sensors), and so forth. But the MAP senor is the big one.

The pleasure of the Sensors

By now, you've probably heard someone say that "every bike runs a little different", and maybe you've wondered why. Didn't all these bikes come off the same assembly line? Didn't the same machine mill all the heads? Isn't it the same configuration, and the same parts? Why do they run different?

It's a fair question. The answer, is that your tune is derived from the plasure of your sensors.

Thing is, no two sensors will report the exact same reading from the exact same thing they are measuring. The reasons for this are many, but the biggest is that Honda doesn't require absolute accuracy from the companies it buys sensors from. They allow a certain amount of variance and error right from the get go. So that MAP sensor from Denso might have a stated accuracy of +- .1v at 90 degrees or whatever. This guarantees right from the start, that you have a certain spread in the tune achieved by the ecu's of all bikes, because there's a spread in what their map sensors are reporting as the manifold pressure. Beyond that, other things can skew the readings reported by the sensors as well - things like outside temperature, dampness in the wires, oxidation in the wire harness, etc. The age and condition of your wire harness greatly effects the resistance of your wiring, and this in turn directly effects the voltages reported by your sensors. Remember Ohm's Law?

Voltage = Amperage x Resistance

So, if you vary the resistance, and the amperage is the same, then the voltage varies. And the ECU reads voltage from the sensors to determine what the sensor is measuring.

So since everyone has a wire harness in different shape, and all the sensors are varying a little in the first place, we end up with bikes tuned all over the map. Thus, we need to find a way to bring our fuel curves back where we want them, and compensate for the error introduced by our wambly sensors.

After Market Fuel Computers

This is a good time to talk about aftermarket fuel controllers, so lets hit on what they do real quick. The 1300 guys can manipulate their A/F ratios by changing jets, but it’s a bit more complex (and expensive) for the 1800 riders. For the VTX, there are basically three types of controller available. All three do exactly the same thing – they manipulate the amount of time the injectors are turned on during the intake stroke, by intercepting the voltage the ECU sends to the injectors. How the decide how much longer or shorter to turn the injector on, varies a bit though, and that variety is important thing to know when selecting which controller to use on your bike (if in fact you choose to use on at all – none of them are ever really necessary, regardless of what pipes or airboxes you add on to the bike.)

It’s also important to understand this: None of these controllers is ever a necessity, regardless of whether you change pipes or airboxes on your bike. The stock ECU will, in almost every case, adjust to the changes in airflow you’ve caused, and give you a reasonably good A/F ratio. But you should understand, that the ECU is not programmed to give you an A/F ratio that is optimized for horsepower from the factory – instead, Honda worries about things like pollution, engine temperature, and rider perception, and so the ECU can be said to be “de-tuned” in order to address these other concerns. Likewise, you have a certain amount of error introduced by your wambly sensors. So the real function of these add-on controllers is to correct the error (or eliminate the de-tuning) that Honda induced in your fuel curve on purpose, and to compensate for the error in your fuel system sensors, in order to reclaim the lost horsepower and improve engine efficiency (possibly at the cost of making more pollution, hearing more deceleration backfiring, etc). Adding on aftermarket pipes or airboxes can sometimes exaggerate this de-tuning as well, so we need to be able to modify our fuel curves to match the configuration of our bikes. Got that? These boxes aren’t really necessary, but if you’re hunting more horses, they can sure find them. Likewise, it's almost impossible to get your bike in perfect tune without one.

So lets talk about the specific boxes:

TFI – This unit is marketed under several brand names by Techlusion, Cobra, DFO, and others. It does one thing, and one thing only – it extends the fuel pulses produced by the ECU, and therefore, it can only richen the fuel mix – and never ever lean it. Typically, these units are designed to act like variable fuel jets – by adjusting two or three settings, you can add more or less fuel to the mix for a certain RPM range – usually low, middle, and high. It determines RPM by looking at the signal frequency produced by the ECU. Because these units are extremely simplistic, they won’t really optimize your fuel curve, although they can reduce or eliminate decel popping, or sometimes correct a really lean condition, But in all cases, your fuel curve will vary from lean to rich along it’s total fuel curve, so you’re only going to help the lean spots, and hurt the rich spots. These units get sold with a lot of pooey about bikes always being lean, or “knowing load”. It’s crap, since we’ve seen hundreds of fuel curves off the dyno now that amply demonstrate that most VTXs run a little lean at low rpms, and rich in higher rpms (as a rule, but not always). This load nonsense is just that, since all of the available fuel controllers modify the signal produced by the stock ECU. Therefore all of them “know load”. Don’t get suckered by marketing malarkey. Frankly, while these units can reduce decel pop, I can’t see that as a goal worth achieving, and so I never recommend these units. I think you can do better, for slightly more money.

Power Commander III – This device also modifies the fuel output from the ECU, but does so based on a table of values referencing the throttle position sensor (TPS), and rpms. Since the position of the throttle plates directly affects the amount of air being allowed into the engine, the value of the TPS is a pretty good substitute for the “Load” value derived from the map sensor by the ECU. In effect, the PC3 produces an overlay curve of its own, and this can be manipulated to correct the de-tuning in the stock ECU, and for sensor error. PC3’s can either lean or richen the mix, and so are capable of completely correcting the fuel curve produced by the stock ECU. Because the new curve is applied proportional to load, its effective regardless of the ambient air pressure – since the curves are proportional. Tuning the PC3 correctly requires a session on a dynometer, so these units are somewhat expensive – but set up correctly, they will produce optimum fuel curves under nearly all conditions. Of course, changing equipment on your bike will mean the curve is no longer a perfect match, and another adjustment session may be required in order to get a perfect fuel curve, so the PC3 is not without its gotchas. But for best performance, the PC3 comes out on top. It’s a very flexible and effective unit. Newer PC3’s also have functions that can emulate a tunable accelerator pump, or allow you to map each cylinder independently. Good stuff.

HPP – This unit adjusts the output fuel pulse by manipulating the value of the MAP sensor, based on calculations derived from reading the oxygen content of your exhaust with an O2 sensor. In theory, this results in a “closed loop” system, one that adjusts itself looking for optimal F/A ratio by reading the exhaust in real time. In practice, the O2 sensors are pretty inaccurate at higher RPMs, and so the device does some educated guessing, and therefore the fuel curve isn’t always perfectly optimized. However, experience has shown that properly set up, these units perform very well, and are an excellent alternative for someone who doesn’t want the hassle of fiddling with their fuel tables, or going to dyno sessions. They can also adapt when new equipment is installed on the bike. So this is the unit to use when performance with convenience is your goal, and you are willing to give up a few percent of horsepower to gain that ease of use. Decent stuff, not perfect. Unfortunately, these are no longer being made, so a used one is the only way you'll find one. Note also, no support, no repairs available, etc.

"Alpha-N" fuel controller - This unit has been recently released, and claims to be a fully closed loop system - meaning it uses feedback from an O2 sensor to optimize itself at runtime. Like the PCIII, it uses the throttle position sensor and RPM to determine an approximation of the load currently placed on the bike. It uses narrow band sensors only, so the accuracy of the Fuel/air ratio measurement is rough, and so it will tend to produce more accurate results at cruise, than under acceleration. However, this unit is so new, that we have very little experience with it here on VTXOA. And so we'll have to wait and see how it will perform. In theory, it could be a very good box, but experience has shown that the gap between theory and fact is often wide, and so some skeptical thinking is required here when considering it for purchase. Once I've gotten one of these on a dyno, I'll revise this and report on it's efficacy. As usual, it comes packaged with the usual outlandish marketing claims. It's also fairly pricey, although it could be considered comparable to a PCIII + a custom dyno tune.

Alas, there is currently no unit on the market which can manipulate the timing tables, and that sucks. These big motors cry out for the ability to optimize timing tables to match configuration or changes to the fuel tables, and there’s no doubt that 4 or 5 horsepower lurk in the inability to manipulate the spark. Perhaps someday Dynojet will follow through on their promises to provide a timing module, but until then, the ability to manipulate spark effectively simply doesn’t exist. I yearn for a fully programmable ECU. I also yearn for a 20 year old hottie with great legs and big boobs. I’ll probably get my timing before I get the boobies though – more’s the pity.

Burn Baby Burn

The last thing I want to address today is the subject of deceleration backfire, or “popping”. This topic generates a lot of concern from inexperienced riders, or even from experienced guys who just hate the noise, so lets take a look at what causes it. But first things first, lets define the issue:

Deceleration Backfire is caused by fuel burning in the exhaust manifold or header.

No ifs ands or buts, thatÂ’s what causes it. But the bigger question is how does gas get there in the first place, and thatÂ’s a bit more complicated. Generally, there are a variety of ways it gets there, and a variety of things that can make the backfiring worse. But thereÂ’s a kicker, and something you should understand before we go any farther:

A motor in perfect tune will exhibit deceleration backfiring.

Therefore, just because your motor is banging it up, doesnÂ’t mean thereÂ’s anything wrong. And consequently:

Getting rid of the noise means de-tuning your motor.

Yup. If youÂ’ve jut got to eliminate that popping, youÂ’ll have to accept the fact that your motor is going to be forced to run rich to do it, and that isnÂ’t necessarily a good thing. So lets talk about what causes the problem.

Ok, so you’re riding along at some given rpm, and suddenly you decide to decelerate, and you reduce the amount of throttle. This causes an “overrun” – that is, the motors rpm is turning faster than the fuel provided can support, so the motor begins to spool down. This causes a couple of things to happen.

First, when you close the throttle, you are also closing the throttle plates. This reduces the air and fuel flowing into the motor, and increases the vacuum (lowers the pressure). This results in less air and fuel in the cylinder during the power stroke, which in turn results in a lower pressure in the combustion chamber. Remember I said earlier, that the A/F mix burns faster in proportion to the pressure applied? Well, when we reduce pressure this way, the mix burns slower. This results in two things happening.

1. The lower burning fuel generates less heat, and the cooling effect of the non-burning fuel tends to “quench” the flame front, or slow it down even further. Because the mix is burning much slower, the exhaust valve can open before all the fuel is consumed, and the unburnt fuel is ejected into the exhaust.
2. The engine designers, in order to promote smoother idling and better combustion, retard the spark when the throttle is shut, and this results in the mix being lit later.

So, now we end up with unburnt fuel in the exhaust, and burning fuel being ejected into the exhaust, and bang! Backfire. In addition, Honda has added a device called a “programmed air injection valve” (Pair Valve) that actually injects some fresh air into the exhaust to help this process along – since fully burning the fuel results in cleaner exhaust. So the backfiring is not only a normal part of the engines operation, it’s also intentionally amplified by Honda! Of course, normally, that massive bazooka pipe Honda hangs on your bike hides most of the noise, but it’s there, even when you can’t hear it.

So the bottom line, is: That backfiring is perfectly normal and expected. If you’ve just got get rid of it, that’s up to you. You’re entitled to set your motor up the way you want, and your goals are your goals. But don’t refer to it as “fixing” the popping. Rather, the correct way to think of it is “de-tuning a bit to get rid of the popping”.

There are a few ways you can do this.

First, use the stock pipe. It will hide the sound, by absorbing it into mass, and masking it with the larger baffle space. Second, you can add more fuel during deceleration. This has the effect of raising the chamber pressure slightly, which burns a little more before the exhaust valve opens. Lastly, you can remove the Pair valve, which reduces the amount of available oxygen in the pipe to burn the unburnt fuel.

Well, there you go. I hope this long piece has given you some information you can use, or clarified things a bit for you. I may ultimately add to this, and discuss valve timing, the effects of compression on performance, or other topics as they motivate me. In the meantime, feel free to criticize, correct, or just tell me how dumb I am. IÂ’m still learning too, after all.

[Duc]

Excellent read but shouldn't you be working on your bike :lol: What ever came of the ins. B.S.? Did they pay up?
Clif

[Tapper]

Actually, I blew out my back, and i've been laid up in bed all day. Nothing else to do, so I've been writing.

Still hassling with insurance companies, but making progress on the bike. Can't ride right now anyway, but hopefully by the time its fixed, I'll be able to ride again.

[David]

I hope so too. Get well soon, and thanks for all your hard work!

[silvervtx04s]

Nice piece Tapper.

[Scarecrow]

Tapper,

A most excellent post. Glad someone pubically acknowledged what I have been saying all along........that the stock ECU can self adjust (to an extent) to match air box and pipe mods and that aftermarket fuel managers are not always needed.

A couple of items. First, in the section on the four stroke engine, you say.....

"The vacuum (area of low pressure) created in the intake manifold is the power that drives the fuel system, and gets the fuel into the cylinder where we want it. The larger the vacuum (lower the pressure), the more fuel is pumped into the cylinder. The faster the piston moves downward in the cylinder, the bigger and faster the vacuum is created, and the more fuel gets pumped. Therefore, it also follows, that the higher the engineÂ’s RPM, and the harder an engine is working, the higher the vacuum (or lower the pressure) exists in the intake manifold."

I thought from my college thermo class (yep, its been a long, long time and I may be fuzzy) that the vacuum created in the engine was strictly based on the compression ration of the cylinder (open volume vs closed volume). That would make both vacuum and compression independent of RPMs. Regardless of how fast the engine is turning, the compression ratio should be constant. But it occurs at a faster pace, meaning the engine is working harder and the load has increased.

Just a minor point.

Also, please say something about the octane issue. There are a lot of folks on this board and others that still think that 91 or 93 octane will make their bike "run" better, not understanding that higher octane gasolines simply allow an engine to utilize a higher compression ratio without the fear of preignition. Higher octane fuel is a myth propogated by the oil companies, like the mandatory 3000 mile oil change.

BTW, I agree about the ignition timing. Until we can vary the timing on the fly, the VTX will never truly utilize all the ponies it is capable of producing.

Once again, great post!

Scarecrow

[HANDLER]

Outstanding piece and not to be taken litely in terms of the time it takes to write such a nice article. I always did wonder how these darn engines worked?
:wink:
Mike

[Dan Osier]

Hey Tapper,

What are your credentials? I have a son that see's me believing that we have some credible experts on this forum, and he thinks I'm gullable for trusting some of the info. around here.

Thanks for the info. i truely appreciate it and up till now I was tron between getting rid of the popping and keeping it because it sounds awesome. I'll keep the popping and tune it on the Dyno to maximize the appetite of H/D's for lunch.

Thanks again!

[Tapper]

"The vacuum (area of low pressure) created in the intake manifold is the power that drives the fuel system, and gets the fuel into the cylinder where we want it. The larger the vacuum (lower the pressure), the more fuel is pumped into the cylinder. The faster the piston moves downward in the cylinder, the bigger and faster the vacuum is created, and the more fuel gets pumped. Therefore, it also follows, that the higher the engineÂ’s RPM, and the harder an engine is working, the higher the vacuum (or lower the pressure) exists in the intake manifold."

I thought from my college thermo class (yep, its been a long, long time and I may be fuzzy) that the vacuum created in the engine was strictly based on the compression ration of the cylinder (open volume vs closed volume). That would make both vacuum and compression independent of RPMs. Regardless of how fast the engine is turning, the compression ratio should be constant. But it occurs at a faster pace, meaning the engine is working harder and the load has increased.

Scarecrow,

Bear in mind that while the maximum and minimum intake pressures possible are a function of the cylinder volume at BDC, the actual amount of air drawn into the cylinder is a rate - i.e. so many cubic feet per minute. So the higher the RPM at a given pressure, the higher the CFM produced. Or more specifically, the maximum vacuum is a function of the cylinder volume across the intake cam duration. Perhaps I could have made that clearer.

[Scarecrow]

Tapper,

Agreed!!!


Scarecrow

[j1mmyj4m]

Hey Tapper,

What are your credentials? I have a son that see's me believing that we have some credible experts on this forum, and he thinks I'm gullable for trusting some of the info. around here.

Thanks for the info. i truely appreciate it and up till now I was tron between getting rid of the popping and keeping it because it sounds awesome. I'll keep the popping and tune it on the Dyno to maximize the appetite of H/D's for lunch.

Thanks again!

I would trust those who are consistant in there posts and provide links/examples/experiences in the area they are explaining. Make sure they stand by their reasons. Tapper is one of the good guys. Tell your son he does his homework and doesn't post if he doesn't know.

[Bob Hamby]

Tapper, great job, thanks for putting all that info together. I finally feel at ease after reading your article. For the last two weeks I have been trying to find out why my bike decel backfires, I don' mind the sound. at first I thought it was just the nature of a high performance engine. I have done all the fixes, de-smog, ground fix, pair covers, intake / exhaust clamp torque and spark plug check. Last nght when I took the bike out it still backfired therefore I concluded it must be running lean and I would have to buy a fuel manager. Would I be correct in thinking I can open up my airbox and the ECU would adjust the injector pulse for the increased air flow without an aftermarket fuel manager? By the way my plugs look almost new they are so clean, 3k on them and the bike ran strong at the drags.
Thanks again for putting together a great post.
Bob

[Robnfl]

Thanks for the informative post Tapper! Now I guess I can send my new FI2000 back. I got it as a pre-emptive strike against the dreaded “decel popping” that I’ve read so much about. Yesterday, I installed bigshots and after a few test rides I was wondering what the big deal is about the “decel popping”? Our engine, with a louder exhaust, sounds like every other engine that I’ve ever hot-rodded over the past 30 years. It’s just a part of a well tuned engine, and made more noticeable with the aftermarket (louder) exhaust.

Rob

[wot]

Thank you,Tapper!Very clear an informative.

[ataDude]

...ching..... another winner from the man. Thx, Tapper. :wink:

[Gumby812]

Great post Tapper.. Once again the 'post whore' title is earned... Keep up keeping us informed! :tools1:

[Tapper]

Tapper, great job, thanks for putting all that info together. I finally feel at ease after reading your article. For the last two weeks I have been trying to find out why my bike decel backfires, I don' mind the sound. at first I thought it was just the nature of a high performance engine. I have done all the fixes, de-smog, ground fix, pair covers, intake / exhaust clamp torque and spark plug check. Last nght when I took the bike out it still backfired therefore I concluded it must be running lean and I would have to buy a fuel manager. Would I be correct in thinking I can open up my airbox and the ECU would adjust the injector pulse for the increased air flow without an aftermarket fuel manager? By the way my plugs look almost new they are so clean, 3k on them and the bike ran strong at the drags.
Thanks again for putting together a great post.
Bob

It should run fine, but you may not get much benefit from the opened up airbox without a fuel controller.

[RamMan03]

Thanks Tapper. I just picked up my 2003 1800C today and the first thing I posted on this site is a question about decel popping. VTXGreen linked this thread in his response to my question. Your article is just what a new VTX owner like myself needed. Thanks again.

[Yak Fishin Fool]

Wow, I learned more here in 10 minutes than nearly every other MC article I've read. Very good. You should really try to get that published.

Comment. The diaphragm contracting actuall creates a negative pressure in the lungs and your lungs, being soft andplaible expand to fill the void. In doing so they create negative pressure (vaccuum) in the trachea and upper airway which then creates a lower air pressure than out side your body and the air rushes in. Relax your diaphragm, and the chest creates positive pressure, collapsing the lungs and you exhale.

Now for you smokers...by smoking, you take those nice soft and pliable lungs and stiffen them. So you have to breathe deeper or harder, with more contraction to create enough negative pressure to get air to enter. eventually the stiffening is so bad, that there is no pliability left, no muscle of the diaphragm left to contract, and the air barely makes it in. emphysema, COPD, and a generalized loss of lung accomodation(movement). Ultimately, lower oxygen levels and eventual failure of the respiratory system.

so there is your health lessen, gleaned from a MC lesson..Again thanks for the info, and smokem if you got'em. Scott

[bhill18]

If the popping is caused by unburned fuel in the exhaust pipe, why does it go away by richening the mixture with a techlusion? Not disagreeing, just curious.

[Tapper]

If the popping is caused by unburned fuel in the exhaust pipe, why does it go away by richening the mixture with a techlusion? Not disagreeing, just curious.

I covered that didn't I?

[6FT8INER]

I WAS AT THE MID OHIO RACE TRACK LAST WEEKEND WATCHING THE SPORT BIKE RACES. I NOTICED THAT THESE FACTORY SPONSORED BIKES HAD DECELL POPING. THESE ARE THE BEST BIKES AND RIDERS IN THE WORLD. OBVIOUSLY DECEL POPING ISN'T AN ISSUE.

[RPJones]

Tapper....
Great article! I am a new owner of a 2003 Retro and was rather apprehensive about some of the things I had read on this OUTSTANDING forum. You cleared up one of the areas of concern, because I did not know why the decel popping was a problem, normal or just a mystery. I own a 900 HP drag car and it will occasionally "pop" during shutdown. Always my first clue to look for a header leak. Thank you for clarifying the cause in the VTX.

On to the garage and doing the "Ground Fix" and the "Surge Fix" for my peace of mind. More GREAT information.

P.S. Yes, I took advantage of the deal on the the leftover 2003 models and it is the finest bike I have ever ridden. My old H?D is "farm equipment" by comparison. The used vehicle prices will rebound as soon as the 2003s are sold out.

Ran

[Tapper]

Glad you found it useful...

[ThreeD]

If there was ever a post that deserved a "sticky" on the Tech board... this should be required reading for anyone changing pipes/airbox and concerned about the "need" for aftermarket FM. Are you going to add this to "Tapper's Garage" on the TXR site?

[Rail]

Trapper,
Out of the hundreds, if not thousands of msgs read on this excellent board, this is the finest example of knowledge with continuity throughout the entire descriptive structure of a msg. You definitely know your VTX, engines in general, as well as how to write.

I agree with another msg above, this should be expanded upon and published. There was so much to learn from the content which was easy to read, with each lesson building on the last.

As an avid Stephen King fan, your writing skill is equal, although the anithesis of his genre. Whereby, the outcome is not scary, wierd or unworldly.

[papajoe]

Best post I have seen on this board. GOOD information. THANKS for taking the time it is appreciated.

[BDC]

Bear in mind that while the maximum and minimum intake pressures possible are a function of the cylinder volume at BDC, the actual amount of air drawn into the cylinder is a rate - i.e. so many cubic feet per minute..

Damn, is that all I am to you?? "Bottom Dead Center"???

Crip!! LOL

Thanks for coming over today Tap, as always my pleasure buddy!!

Also thank the Ricster, GermanPete and Brokenwing for showing up...

Just wish all the TX X Riders would of shown up!!!

http://im1.shutterfly.com/procserv/47b4d910b3127cceb30eebdea1110000001610

THanks for the invite and the burgers, you aint have bad grill cook, My wife and I thank you again for you and Michelles hospitallity...

Pete and tapper and broken wing..great to get to yack at you again.

Pete, Bottem dead Lost , broken will see you in the AM...bright and early!!

you guys rock!!

[Tapper]

Yep, good to see y'all again...

[wot]

MODERATOR!Please consider making the original post of this thread the first tech board "sticky" Any more votes?

[Tapper]

Well, since I'm the moderator, it seems sorta like self lovin for me to do that. I suppose you could always pmsg Lamont though.

[ThreeD]

MODERATOR!Please consider making the original post of this thread the first tech board "sticky" Any more votes?

Well, the post already has my vote for sticky. But understand that Tapper is the moderator of this board as well as the author of the post. We may not want to put him into the uncomfortable position of voting.

[ThreeD]

MODERATOR!Please consider making the original post of this thread the first tech board "sticky" Any more votes?

Well, the post already has my vote for sticky. But understand that Tapper is the moderator of this board as well as the author of the post. We may not want to put him into the uncomfortable position of voting.

DOH! I guess I didn't type fast enough.

[Brokenwing]

Also thank the Ricster, GermanPete and Brokenwing for showing up...


Thanks again for the invite BDC. I enjoyed it. I like that picture too; notice how everyone is looking at Tapper in that pic? He seems to be sharing his wisdom with us there too... Seem fitting for this post!

Later,
Scott

[Tapper]

Either that, or I had some mayo on my chin or something :)

[silvervtx04s]

Is this Mayo on the chin a technical issue ?? :wink:

[Bareass172]

Please Tapper PLEASE - sticky this article. I know you wrote it but maybe - JUST MAYBE - it might stop some of the "do I need a fuel manager, what kind? What kind of pipes/intake?" questions we get all the time. :D :wink:

[jwalker]

Tapper,

Excellent article. Everything you said is true and all should heed this information.

Do you have a soft copy of the logo used with your signature and would you consider letting other Texas VTX riders have some shirts madeup with it>

Jerry Walker

[Mowoc]

Tapper,

In your response to scarecrow you stated the following:

Bear in mind that while the maximum and minimum intake pressures possible are a function of the cylinder volume at BDC, the actual amount of air drawn into the cylinder is a rate - i.e. so many cubic feet per minute. So the higher the RPM at a given pressure, the higher the CFM produced. Or more specifically, the maximum vacuum is a function of the cylinder volume across the intake cam duration. Perhaps I could have made that clearer.


Being somewhat new to this I was wondering a few things. I think I answer my own questions below, but.....

1. Obviously there is a cap to the amount of air that can be drawn into the cylinder, right? Is there a way to determine the maximum pressure on the fly? What I am getting at here is how do I remove restrictions on the air flow to ensure I max out the pressure in the cylinder during the intake? Do I want to do this, or is there some sort of catostrophic engine failure lurking around here that this newbie is unaware of?

2. I think this may be the answer i am looking for, but I guess I am testing myself. If I put a new cam shaft in that has a longer intake valve duration am I fixing this issue?

3. Does the X have any issues with to little fuel getting added to the mix? I am specifically asking about the 1800. Based on reading this I would bet that you would need to reject the 1300 at some point if you introduced enough air, is there some sort of fuel injector fix or does the fuel injector handle any flow of air possible up to the limit mentioned above?

I hope these questions make sense, I am not an engineer but I am trying desperately to understand this process. This stuff is fun to figure out!

[VTeXan 1800]

That was a damn fine article. Thank you for the time and effort that it took. You are now officially on the long list of reasons why I'm proud to be a Texan. Also, don't forget to put it on the TexasX board. I hope it's not much longer before I get the opportunity to meet you.

Brian

[Tapper]

Tapper,

In your response to scarecrow you stated the following:

Bear in mind that while the maximum and minimum intake pressures possible are a function of the cylinder volume at BDC, the actual amount of air drawn into the cylinder is a rate - i.e. so many cubic feet per minute. So the higher the RPM at a given pressure, the higher the CFM produced. Or more specifically, the maximum vacuum is a function of the cylinder volume across the intake cam duration. Perhaps I could have made that clearer.


Being somewhat new to this I was wondering a few things. I think I answer my own questions below, but.....

1. Obviously there is a cap to the amount of air that can be drawn into the cylinder, right? Is there a way to determine the maximum pressure on the fly? What I am getting at here is how do I remove restrictions on the air flow to ensure I max out the pressure in the cylinder during the intake? Do I want to do this, or is there some sort of catostrophic engine failure lurking around here that this newbie is unaware of?

The absolute cap is the volume of the cylinder at BDC, however, this is functionally limited by a several things, the most important being the intake cam duration, and the flow rate of the manifold assembly. These factors can be manipulated, either by changing cams or by porting the heads, modifying the manifolds, polishing, etc. Maximizing the air charge is part and parcel of hot-rodding the motor, since it's a lot easier to squirt in more fuel than it is to get more air in. As to failure, any time you increase horsepower, you also increase stress on the motor - and increase the possibility for failure. There's always a trade-off.

2. I think this may be the answer i am looking for, but I guess I am testing myself. If I put a new cam shaft in that has a longer intake valve duration am I fixing this issue?

You can put in new cams to increase the duration or lift, and this can result in getting more air in, yes. You can also reduce airway restrictions in the air intake systems, like adding a higher flow air filter, increasing the airbox orifice diameters, increasing the size of the manifold itself, porting the heads, etc. All will increase the size of the air charge.

3. Does the X have any issues with to little fuel getting added to the mix? I am specifically asking about the 1800. Based on reading this I would bet that you would need to reject the 1300 at some point if you introduced enough air, is there some sort of fuel injector fix or does the fuel injector handle any flow of air possible up to the limit mentioned above?

The 1800 is typically programmed lean through the first 2500 rpms or so, and rich thereafter. The ECU will handle increases in air flow up to a certain extent, but will not necessarily provide an optimum A/F mix - for that you need an aftermarket device like the PCIII, HPP or TFI units.

I hope these questions make sense, I am not an engineer but I am trying desperately to understand this process. This stuff is fun to figure out!

Makes sense, and you're right, figuring all this stuff out is a lot of fun!

[IguanaMan]

I'm a new '03 VTX 1800 owner, still trying to get used to the power of this bike. Your post was extremely informative. I was aware of the basic of 4-stroke combustion engines, but your level of detail and clear explanation definitely took my understanding to a higher level.

Thanks and please keep up the good work.

[wot]

BUMP,STICKY!

[Tapper]

Ok, I surrender. Sticky it is.

[Bareass172]

Ok, I surrender. Sticky it is.
YAY! :D

[MrFixit]

Thanks Tapper, it is not self serving, and it makes good sense especially with this recent influx of new members...You have certainly made my ride more reliable, powerful and pleasurable.

:idea: and Bare, here's an idea :arrow: When are you going to quit your day job and open a shop of your own? :D

[Bareass172]

:idea: and Bare, here's an idea :arrow: When are you going to quit your day job and open a shop of your own? :D
As soon as wrenching on the side can pay my bills. :D

[1badVTX1800]

Tapper, interesting article. Great way to explain everything.

Just a quick question.....

What we're saying with the decel pop is combustion occuring the manifold or exhaust pipe right? Isn't that a bad thing over time? Just curious.

[Quicksilver-X]

X-elent!

GREAT Job Trapper... Just as I had been telling myself why do I want to put something on my Bike to richen the A/F ratio., I can look at my pipe tips and see all the carbon from the rich tuning.. So I kinda like the HHp since it is the one wiith the O2 sensor.but like you say that is not enough..So I will wait until something else comes along..

Oh yes the Decel problem I put on my Bigshots and said wow I have a exhaust leak.. read my Manual and found out like you say Honda injects Air under decel I guess this reduces Hydrocarbons. My Popping was severe until I reduce the rpm usiing the idle Screw.. I guess this allowed the butterflys to close more preventing more full being injected.. also I had to learn to fully untwist my wrist to acheive this. but it sounds so much better... My 3 cents worth..

[Brand X]

Outstanding review. Thank you.

[BBWolf]

I wanted to extend my appreciation for the excellent article Tapper, thank you so very much. I always did like a little decel popping anyway, and now I know that the bike is performing normally, and so much more! The article is clear, concise (eventhough a little long), and exceptionally well written. Thanks. Say, this is my 100th post.... :wink:

[Rowder]

Trapper...
I'm thinking of carving a design on my airbox cover to let more air in. Will the onboard sensor adjust for the extra air, or am I going to need a fuel management unit?

Thanks,
Rog

[Tapper]

Trapper...
I'm thinking of carving a design on my airbox cover to let more air in. Will the onboard sensor adjust for the extra air, or am I going to need a fuel management unit?

Thanks,
Rog

It well, but bear in mind it will also exagerrate "error" Honda programmed in for emission purposses, and sosmetimes this can get to the point it causes problems. Try it and see.

Guys, it Tapper. T - A - P - P - E - R. There's also a Trapper on this board, and while he's probably a good guy, I doubt he'd be thrilled to be mistaken for my ugly mug.

:oops:

[Bareass172]

Guys, it Tapper. T - A - P - P - E - R. There's also a Trapper on this board, and while he's probably a good guy, I doubt he'd be thrilled to be mistaken for my ugly mug.

:oops:
I was wondering how long it would be before you mentioned the "silent 'R'". :lol: :lol: :lol: :wink:

[Rowder]

Thanks, Tapper..... my humble apologies for the typo.... was having a "blonde moment" LOL.
Rog

[Okie]

Great Stuff,

Going to be mandatory reading for both of my sons: yes, there will be a test.

Also, forwarding to a math teacher friend. Could give some of the young guns in her class some reason, backed by practical application, to understand trig.

Thanks Bro.

[Old Rider]

Good write-up. It refreshed my memory on engine performance from my study of automotive technology in 1997-1999. Yours is a good verbal description of what happens or is happening in a computer controlled engine.

[Maniac66]

WOW!!!!!!! :shock: that was an awsome write up Bro!! I'm a Navy jet mechanic and been workinig with engines for 18.5 years (in the Navy), but that piece just blow's me away. I'm new to the VTX world, but not new to bikes and Hot Rodding. I do feel that I am better educated now on how this 1800 motor works, with all the new computer stuff on it, I'm old school here! Carburation Baby!! 8) but in the jet world we have some of the simular things, but instead of a fuel injected carb system we use a fuel control, which cost more that 10 VTX1800's new!! Tapper, great job! I too feel at ease with this thing, and well worded for the little guy's like myself :D . I look forward to seeing more of your tech stuff. Are you open too questions if I have any on theis bike??

[Tapper]

I'm always open to questions, but all you really need to do, is post the question here on the tech board. There's a bunch of knowledgeable folks here that will try and help, and several more knowledgeable than I.

[bigbore]

Tapper,

Great post. This is a really helpful site and posts like yours are invaluable in clearing up issues and questions many of us have. Like the octane issue, it's much easier to make good decisions when you know the facts. Keep writing. There's a lot of mis-information out there that needs the light of truth shined on it. This site is the coolest thing I've ever found on the internet.

Bigbore

[HANDLER]

Say Tap, have you given much thought to the differences in the CA model ECM as apposed to the 49 state models in terms of efficiencies in adjusting F/A ratios? Given their partial closed loop configuration and use of an O2 sensor for feedback in the low end rpm's, I've always wondered what the fuel curve looks like on a CA bike as apposed to a 49 state model. Likewise, one would wonder if a CA model would be more or less likely to experience Decel popping all things being equal.
Mike

[Tapper]

You know, I've seen almost no data on the CA models with respect to the O2 sensor. ECU's can use them in so many ways, I can't even speculate without being able to play with one a while.

Lower quality O2 sensors tend to be used to build modifier values by doing some simple statistics on readings at various rpms. I'm going to guess that's what the Honda sensor is doing, but it's just a guess.

[JPVTX1800]

I read your entire article. Another reader asked and i think rightly so why does enrichening the fuel cause the popping to go away? That was the first question that came to my mind. You said you covered that. You did say if you ran rich it would quiet it down but did not explain why. It sounds like two opposing principles. I had pipes put on my bike and the honda shop did not nothing to the Power Commander III USB except load a stock 2003 1800C map into it. It popped and to be honest did not have all the impressive "power" i have been hearing everyone rave about. I tuned the Computer up for richer and i have about 25% more power in my bike. The bike was starved! It runs smoother and has power through out the curve and sounds better. Deeper rumble almost no popping. I pulled the plug after a good run and it was not running wet or black. So although your engine 101 article is good, the two opposing principles you suggest dont make any damn sense to me.
JP

[bhill18]

I've been thinking about that since I posted. For combustion you need the right mixture of fuel, air, and ignition, whether it's in your cylinder or your exhaust pipe. I've been weighing some options
1. The added gas slows the combustion in the exhaust pipe so it burns more controlled, and doesn't pop as much.
2. The added gas changes the mixture, makes it too rich, and the combustion never starts.
3. The combustion in the cylinder is more complete, leaving less unburned fuel for the pipes
4. The added fuel keeps the cylinder cooler, the unburned fuel in the pipe does not get ignited.

What are your thoughts?

[Tapper]

Richening up the mix reduces popping because it leaves more gas in the cylinder during overrun, which tends to slow the flame front during overrun (due to low pressure effects) to the point where it won't burn fast enough in the exhaust to make any noise.

[HANDLER]

deleted

[Tapper]

I read your entire article. Another reader asked and i think rightly so why does enrichening the fuel cause the popping to go away? That was the first question that came to my mind. You said you covered that. You did say if you ran rich it would quiet it down but did not explain why. It sounds like two opposing principles. I had pipes put on my bike and the honda shop did not nothing to the Power Commander III USB except load a stock 2003 1800C map into it. It popped and to be honest did not have all the impressive "power" i have been hearing everyone rave about. I tuned the Computer up for richer and i have about 25% more power in my bike. The bike was starved! It runs smoother and has power through out the curve and sounds better. Deeper rumble almost no popping. I pulled the plug after a good run and it was not running wet or black. So although your engine 101 article is good, the two opposing principles you suggest dont make any damn sense to me.

Hum......? Makes a lot of sense to me, and I'm not even all that smart :-)
mike
JP

First, if you'll read the directions on your PCIII, I think it pretty clearly states: You need to take your bike with the PCIII installed to a dynojet tuning center, and have a custom map made. Just jacking in more fuel might help in some places, but it will hurt in others, and end up ruining your gas mileage. Every bike is a little different, a custom maps means you should be in perfect tune. No map, means you are not in perfect tune - by definition.

Second, dumping a "factory vtx" map in, just means loading a map with all 0's in it - and therefore the PCIII is doing nothing whatsoever to you fuel curve.

[RBrown]

I am thinking about getting the Thunder Tear Drop air box and the PIII but have a couple of questions. I live in a small city in southern Alabama so I don't have any idea where I would get a custom map for my VTX 1800 R. I have Montgomery, Mobile and Dothan that are within riding distance so I guess I could start by contacting bike dealerships to ask if they know where I could get my bike mapped.

My second question is that I was reading some comments and everyone said to make sure to get the jet kit. Is that something you can install on a fuel injected bike? The Thunder product comments state that you can't use their jet kit on a fuel injected bike so I thought it must be some other product that people were referring to.

[Scarecrow]

RB,

The only way to get a "true" custom map is by taking your bike to a dealer with a dyno that know how to program the PC III properly. I would think only the larger towns in your area would have this capability. But make sure they really know how to properly program the PC III and aren't just doing a plain ole dyno run.

Second, the 1800 is fuel injected so there are no jets. All the changing is done electronically by the PC III.

Scarecrow

[RBrown]

Thanks, Scarecrow. I'll have to make some calls or ask on the Alabama VTX board to see if anyone knows of a knowledgeable dealer that can dyno correctly.

[JPVTX1800]

Hum......? Makes a lot of sense to me, and I'm not even all that smart :-)
mike


My point is that when you say a detuned engine has no popping noise and a tuned engine back fires or pops it is a subjective statement. Your definition of a bike that backfires (like its supposed to?) and my definition of proper back fire or lack thereof is superfluous. The real answer is getting the bike on the dyno. You cant tell someone an engine is right because it backfires. You may be giving them the wrong information and a biker is riding a bike that is starving for fuel. Not good for the bike right? I know on the side of lean is the enviormental concerns and I am sure the Honda company line that leaner is better. Anyway i guess your right you arent that smart, at least you didnt get what i was getting at.

JP

[HANDLER]

deleted

[JPVTX1800]

This board is a community of people who help each other. It is contructive. It is free of insults and trash talk. I suggest that you keep these offensive remarks off the board This is very unusual conduct for this board and I doubt anyone appreciates it. Mike

Actually i appreciated this article and this board very much. I have learned so much about my bike on here. I was digging into a certain aspect of this post. These guys on this board have set me in the right direction on understanding the questions i have about my VTX1800 and i am very thankful. The comment on smartness was a response to your comment. So if it offended you dont make comments like that or get a thicker skin.

Joseph

[HANDLER]

deleted

[Tapper]

My point is that when you say a detuned engine has no popping noise and a tuned engine back fires or pops it is a subjective statement. Your definition of a bike that backfires (like its supposed to?) and my definition of proper back fire or lack thereof is superfluous. The real answer is getting the bike on the dyno. You cant tell someone an engine is right because it backfires. You may be giving them the wrong information and a biker is riding a bike that is starving for fuel. Not good for the bike right? I know on the side of lean is the enviormental concerns and I am sure the Honda company line that leaner is better.

First, in no way have I said that "backfiring" was always a sign of a properly tuned engine. Backfiring can also be a symptom of a faulty motor system as well. What I said was, that properly tuned engines frequently snap, crackle, and pop in the exhaust headers (this is not, strictly speaking, backfiring). This is almost a certainty in the VTX, because of the way the ignition timing is set. In a VTX, when you shut the throttle, the ECU retards the timing, on the principle that we want the fuel mix maximally compressed at low fuel flows to promote full burn at idle, and indeed that is important to maintain a smooth idle. However, when the engine is in an overrun state (i.e. when going from a position of relatively high rpm to a position of relatively low RPM), this is exactly backwards - you want to advance the timing a little (light the mix early), to prevent unburned fuel from flushing into the exhaust (and making bang noises, particularly as a working PAIR valve feeds the partially burned mix new oxygen). Note- This suggests that the ECU relies heavily on the TPS sensor to determine ignition table values.

[JPVTX1800]

First, in no way have I said that "backfiring" was always a sign of a properly tuned engine. Backfiring can also be a symptom of a faulty motor system as well. What I said was, that properly tuned engines frequently snap, crackle, and pop in the exhaust headers (this is not, strictly speaking, backfiring). This is almost a certainty in the VTX, because of the way the ignition timing is set. In a VTX, when you shut the throttle, the ECU retards the timing, on the principle that we want the fuel mix maximally compressed at low fuel flows to promote full burn at idle, and indeed that is important to maintain a smooth idle. However, when the engine is in an overrun state (i.e. when going from a position of relatively high rpm to a position of relatively low RPM), this is exactly backwards - you want to advance the timing a little (light the mix early), to prevent unburned fuel from flushing into the exhaust (and making bang noises, particularly as a working PAIR valve feeds the partially burned mix new oxygen). Note- This suggests that the ECU relies heavily on the TPS sensor to determine ignition table values.

Tapper this does make sense to me; i appreciate your commentary.

[RamboX]

JP - if you use the "quote" button, the posts are easier to read, and you don't have to copy and paste the previous message. Thanks.

[CrazyHorse]

Thank you Tapper, I've been riding 30+ yrs.
Your post on how things work was very welcome, I rode my Harley for 14yrs., the only sensor was on the seat. I am new to all the new fangaled sensors
computors, etc. on the X.
Your post gave me some needed insight.
P.S. I did the fuel mod, my stealership had the fuel valve on hand as the dirt bikes use them.

[mikea1126]

Thanks Tapper for this valuable information. I just installed V&H Bigshots and experiencing some popping/backfiring. I'm using the Techlusion Fuel Management System and I've adjusted the POT's and can't seem to find the sweet spot. I knew I was getting popping/backfiring when I had the stock pipes and with a louder exhaust the popping is going to be louder. Now since I know that doesn't mean that the engine is improperly tuned its not a concern.

[mikea1126]

Is removing the Pair Valve the same as blocking off the air injection system? If so, can someone instruct me on how to block off the air injection system. Tech support from Techclusion suggested I block off my air injection sytem to eliminate the backfiring.

[Bareass172]

Is removing the Pair Valve the same as blocking off the air injection system? If so, can someone instruct me on how to block off the air injection system. Tech support from Techclusion suggested I block off my air injection sytem to eliminate the backfiring.
Search for desmog and you'll get a million threads all with enough to get you pointed in the right direction. :wink:

http://www.rwmillerandsons.com/Riley/Ai ... oxDsPs.htm (http://www.rwmillerandsons.com/Riley/AirboxDesmog/ChapterAirBoxDsPs.htm)

Get GP's block-off plates too. :wink:

[mrcisco]

Dam, I learned alot from that, thanks!

[jim cantrell]

man thats a great read ! suck,squeeze,bang,blow....trell

[XHombre]

Thanks Tapper for this valuable information. I just installed V&H Bigshots and experiencing some popping/backfiring. I'm using the Techlusion Fuel Management System and I've adjusted the POT's and can't seem to find the sweet spot. I knew I was getting popping/backfiring when I had the stock pipes and with a louder exhaust the popping is going to be louder. Now since I know that doesn't mean that the engine is improperly tuned its not a concern.

Hey mike

Just finished reading Tapper's "Motors 101" articl and then found your post. Stuck in the unrideable doldrums of Winter, I recently ordered the TFI module('cause I'm to cheap to spring for either the PCCIII or The HPP unit)and Thunder's teardrop airbox. I run an '02 1800C w/ V&H Bigshots, quiet baffles and the blurple beast runs pretty darn good before adding the two new goodies.

My question is this. Do you really feel that the TFi unit added any legitimate benefit to your ride? I'm beginning to think that I may have jumped the gun and purchased something that prvides negligible benefit at best or is totally specious at worst. What's been your experience - mine's still new in the box and returnable.

BTW, the quiet baffles eliminated most of the decel popping, so that is a non-issue. I ride aggressively :D :D so I nevr deviate much from 30 mpg.. I'd appreciate any and all feedback.

Thanks Alot

Philip Berg.....akaXHombre

[XHombre]

Sorry guys - thought the previous post as PMed. My Bad!

[silx04]

Had my bike dynoed and it had a 16/1 ratio is this considered in the ballpark?

[natedawg1972]

where do I get one of the "hpp" units that you describe????

[Bareass172]

where do I get one of the "hpp" units that you describe????
http://www.highperformanceproducts.com/

[XHombre]

Sorry guys - thought the previous post was PMed. My Bad!

[XHombre]

Thanks Tapper for this valuable information. I just installed V&H Bigshots and experiencing some popping/backfiring. I'm using the Techlusion Fuel Management System and I've adjusted the POT's and can't seem to find the sweet spot. I knew I was getting popping/backfiring when I had the stock pipes and with a louder exhaust the popping is going to be louder. Now since I know that doesn't mean that the engine is improperly tuned its not a concern.

Hey mike

Just finished reading Tapper's "Motors 101" articl and then found your post. Stuck in the unrideable doldrums of Winter, I recently ordered the TFI module('cause I'm to cheap to spring for either the PCCIII or The HPP unit)and Thunder's teardrop airbox. I run an '02 1800C w/ V&H Bigshots & quiet baffles. The blurple beast runs pretty darn good before adding the two new goodies.

My question is this. Do you really feel that the TFi unit added any legitimate benefit to your ride? I'm beginning to think that I may have jumped the gun and purchased something that provides negligible benefit at best or is totally specious at worst. What's been your experience - mine's still new in the box and returnable.

BTW, the quiet baffles eliminated most of the decel popping, so that is a non-issue. I ride aggressively :D :D so I never deviate much from 30 mpg.. I'd appreciate any and all feedback.

Thanks Alot

Philip Berg.....akaXHombre

[Crowbar6879]

I have a question, I as well am spending these long ang wickedly cold days planning this spring's round of bolt on goodies, does anyone know how flexiable the oem spark map is, I despise the twin garbage cans on the side of my 04 1800n, they are way too quiet, can't much hear the motor myself, but what I can hear is the beast taking a large deep breath from under the tank, and I don't much care for that either, every time I twist the throttle, I think of trying to take a deep breath through a bendy straw.

[Jimbo]

Hey Tapper, nice job on engine explanation. I have only been a member of this site a short time and am enjoying it. I work for New Jersey transit as an engine/trans. overhaul instructor, have been into bikes my whole life (I'm 50) as was my Dad. If I can ever be of help with tech. please ask. Would like to get involved, seem like a nice site. Jimbo 1800c. JToman@njtransit.com

[Bills VTX]

an air pump?

Someone flunked thermodynamics....

[Tapper]

Actually, I got an "A" in Thermo. I must have missed "What the hell you're talking about" 101 though.

[Perk]

sqeezen and sneezen it , never explained better thanks tapper.

[dizzydean_61]

Good Day to all; I am in the process of buying a 2002 1800s from a local credit union here. The machine has 3k miles. The oil and coolant look very good and physically its in great shape. If it becomes mine the first thing I will repair is the wiring. Wondering if the desmogging is a necessity and are there any other issues that will pose an immediate problem? Also are there any mods that are recommended for performance or is stock just fine? I realize you have probably answered these questions before many times and I appreciate your patience. The last time I rode any bike Kawasaki was still making triples!! I'm sure I just dated myself LOL. I have looked at a lot of bikes and decided on the VTX line. I am beyond impressed with it and am very excited about riding again. Almost like being in love!!LOL. Anyway I am looking forward to further reading and meeting with the WA state riders. Keep up the awsome work here. You ROCK!!!! Dizzy :roll:

[BilltheDiver]

Hereafter you should be reffered to as "Professor Tapper"! Thanks for the illumination.

Besides, I am passing on my 1300C to my youngest son and just bought an 1800N. You made me happy that I ordered the PCIII to compliment it. Nothing like validation of your choices!

[hokiehi]

excellent piece-really filled in the blank spots on my understanding of the dynamics of fuel injection. Am picking up a PC III today from a guy that complained about what it did to his fuel economy. I do know that he never spent the time to have his bike dynoed after his purchase. My gain-

This was also useful info about decel popping. With my sideburners, rapid decel from 80 mph sounds like a 9 mm going off. Now I know not to worry about it, indeed it appears this is a good thing.

This is my first visit to this forum. I really appreciate those that take the time to share their intellectual capital. Thanx ya'll.

Just purchased a leftover '03 1800 s about a month ago. Love the thing to death, it's a fantastic machine. Now, my issue is about the fuel capacity. The specs in the owner's manual says that fuel tank capacity is 5.28 gallons.

Now, I have actually run out of gas, after ignoring the "fuel reserve" light, as I was of the opinion that it comes on too early. After refueling the tank, it took only 4.7 gallons. Does this mean that the bike does not use the remaining .6 gallons? Just wonder what the experience has been with other VTX 1800 rider/owners.

[hokiehi]

good doggone question VTX lifer. I have run my xtreme machine a good 30 miles past a constant glow from the warning light. I know I was getting on the nervous side when I refueled. Quite honestly I can't remember how much it took to refuel. Sounds as if I had reason to be nervous.

[Bareass172]

Just purchased a leftover '03 1800 s about a month ago. Love the thing to death, it's a fantastic machine. Now, my issue is about the fuel capacity. The specs in the owner's manual says that fuel tank capacity is 5.28 gallons.

Now, I have actually run out of gas, after ignoring the "fuel reserve" light, as I was of the opinion that it comes on too early. After refueling the tank, it took only 4.7 gallons. Does this mean that the bike does not use the remaining .6 gallons? Just wonder what the experience has been with other VTX 1800 rider/owners.
Look on my website for the fuel pump mod:

http://www.bareasschoppers.com

These bikes always leave about 1/2 gallon you can't get to.

[RocknRoll]

Great article. Even I understood it. Amazing!!!

Curious though - Can the aldehyde like stink that burns the eyes, nose and throat that is so prevelent on Xs that have a fuel nanny and/or blocked pair valve be addressed by proper tuning of the bike? Isn't that an indicator of a too rich system?

[gene]

I have a problem with my bike, I ride a 2002 Honda VTX 1800C, the bike only has 5000 miles on it and I just started having problems. As soon as I start it up it begans to pop, I also lost a great amount of power on it, I think a MOPED can outrun my bike right now. I can also smell gas (burning very rich) how can i correct this problem. Please reply to my e-mail or if you can call my on my cell phone
Thank You
Janio Luis Martinez
"gene"
janio786@netzero.net
830-968-9171

[Patdawng]

So removing the pair valve is actually detuning the bike. Is there a possibility of damaging the bike in the long run because of this. (05' 1300 Retro)

[Kong]

That was a good article, I now feel I better understand the beast I'm sitting on. After reading and getting familiar with this site, I can now say this is VTX mecca. I bought a used 1800R, 02 from a guy who was ready to quit riding. He told me all about the FI2000 he had installed and what an advantage it was. I guess now, I really know. Since I don't have the funds to go PC111, I suppose your advise is to do the HPP. What does that stand for anyway, and what kind of $ are we talking about to install it? I bought the bike from a person who lives on the coast of South Carolina, I have moved it to the opposite end of the state which is very close to the mountains. Has this elevation change screwed up any settings? This bike is basically stock except for the FI2000 and after market pipes (which I can't find the name anywhere).
Being you have a great deal more experience, what is the first thing I should be working on to make this bike tip top shape? Thanks in advance for any direction you can give me.

[Roger]

Thanks Tapper for the excellent explanation. It is well written and easy to understand and leaves me a little less vulnerable to the marketing guys.

[meesier42]

I WAS AT THE MID OHIO RACE TRACK LAST WEEKEND WATCHING THE SPORT BIKE RACES. I NOTICED THAT THESE FACTORY SPONSORED BIKES HAD DECELL POPING. THESE ARE THE BEST BIKES AND RIDERS IN THE WORLD. OBVIOUSLY DECEL POPING ISN'T AN ISSUE.
Those race bikes do not have a PAIR valve that will introduce fresh air into the exhaust system and allow popping. You must remember that the PAIR valve on the 1800 actually injects the air into the head just downstream on the exhaust valve (prior to the header), where exhaust temps are still ~1100 F or higher. Those race bikes w/o the PAIR valve fresh air doesn't hit the exhaust stream till at or near the tailpipe, here exhaust temps are only ~150 maybe ~200 F. not nearly hot enough to allow spontaneous ignition. Hope that helps

[RocketVTX]

Thanks Trapper, I will no longer worry about the popping. Rocket

[sacred_dog]

wow. what an article.

I think I better tattoo TAPPER across my chest. Now I know the meaning of Life, etc.

Furthermore, if I am not mistaken, the head bone's connected to the neck bone. The neck bone's connected to the...

thanks again,
Tim

[steamroller]

WOW....i went to college for years and years....got all sorts of letters after my name....but i never got to learn what i really wanted to know aout engines till now....thanks

[rab]

nice piece need it in the front of my pages.

[bullshipper]

Thinking of getting a power commander for my vtx 1800. Any thoughts? Is the extra HP worth the $$$.

[Mattathias]

Outstanding article. 8)

[Chicago-Spike]

Thinking of getting a power commander for my vtx 1800. Any thoughts? Is the extra HP worth the $$$.
On a stock bike, no. Just not enough differences from the stock ECU and the stock airbox and pipes. If you were to change the airbox or/and pipes then you would notice the addition of a PC3, big time. 8)

[BIGDAVE55]

So Tapper are you for or against the De-smog ? I was going to do the desmog got the block off plates and ten read your outstanding article now I don't know if I should do the desmog or not... Now I understand my Bike is not a race bike and splitting hairs will not make any diffrence that I can feel, but I don't want to mess up the system, but at the same time if the small change the desmog makes in sound better .... ???
THANKS FOR ALL YOU DO TO HELP US OUT !
Dave

[Chicago-Spike]

The Pair assembly is only an anti-smog device. It injects fresh air into the exhaust ports to help burn off unspent gasses. It is located after the combustion chamber so it has no effect of how the bike will run. By removing the assembly you will only really be cleaning up the top of the motor and ensuring that no condensation will build up inside the system if it was capped or plugged by installing an aftermarket air box. When swapping exhaust pipes removing the pair system will help reduce or eliminate the decell pop we read so much about. No performance gains, fuel mileage increase, just better sounds from the exhaust. Find instructions on removing that on www.bareasschoppers.com/desmog (http://www.bareasschoppers.com/desmog)

[scongo]

I have Cobra drag pipes with cobra fuel manager (came on bike when purchased). So to conclude would the majority say that to desmog, in an effort to reduce or eliminate decel pop, is not the greatest idea because; it may be better to let the fresh air in and burn off the unburnt gasses and keep the exhaust cleaner? Will this burning of gasses blue pipes faster?
I ordered the block off plates and now I'm second guessing myself on what to do!

Thanks again everyone

[Chicago-Spike]

I have Cobra drag pipes with cobra fuel manager (came on bike when purchased). So to conclude would the majority say that to desmog, in an effort to reduce or eliminate decel pop, is not the greatest idea because; it may be better to let the fresh air in and burn off the unburnt gasses and keep the exhaust cleaner? Will this burning of gasses blue pipes faster?
I ordered the block off plates and now I'm second guessing myself on what to do!

Thanks again everyone
No, it IS better to do the desmog instead of pooring fuel at the problem with a fuel manager. The pipes won't blue because you remove the pair system. 8)

[tnretro]

Tapper - recently had the spark plugs replaced by the Honda shop. They are under the impression that the reason they needed replaced after 10,000 miles was due to my not plugging the air line for the PAIR. I have an aftermarket air box and pipes (Kury hyper-charger and Jardine Rumblers) and have been running with a Harley crankcase filter on the vacuum line since there's no place to plug it into the air box.

I'm sceptical about the reason for the plugs needing replaced. The Honda shop bolted the covered the air line. Now the bike sounds different - and I don't like it :x so I'm thinking about getting another filter and trying that.

Your thoughts?

[Chicago-Spike]

Tapper - recently had the spark plugs replaced by the Honda shop. They are under the impression that the reason they needed replaced after 10,000 miles was due to my not plugging the air line for the PAIR.
That is just false. The pair system is after the combustion chamber so it would have little to no effect on the plugs.
I have an aftermarket air box and pipes (Kury hyper-charger and Jardine Rumblers) and have been running with a Harley crankcase filter on the vacuum line since there's no place to plug it into the air box.
That line is not a vacuum line, that is the crankcase vent line that will have to have a breather on it. The vacuum lines are the very small lines(1/4 inch outside diameter) See the pictires of the lines here;
www.bareasschoppers.com/desmog (http://www.bareasschoppers.com/desmog)

I'm sceptical about the reason for the plugs needing replaced. The Honda shop bolted the covered the air line. Now the bike sounds different - and I don't like it :x so I'm thinking about getting another filter and trying that.

Your thoughts?

The pair system should be removed for one reason, condensation. Condensation will build up inside the plugged pair system hoses. This water has been known to be sucked back into the engine causing a nice steam show out the pipes. While it looks bad, it's not to bad for the engine because it's running and hot enough to burn that water off. What worries me more, is when the bike sits and if water was to drip out into a cold engine all the corrosion that water could start up inside the engine.

All the aftermarket airboxes are going to com e with instructions to plug the pair system. Barons airboxes even include a set of "Block-off plates" to remove the entire system as I am suggesting you do. HDL has plates for sale as well. You remove the paior system and you will like the sound after that.

[XMich]

Last week I installed the Kuryakin Hypercharger and Wild Things Injection Controller on my X1800. I have a gutted out stock pipe cut down. I used the recommended specs on the injection controller, but did not get the results I was looking for. Does anyone have this or a similar set-up that can give me some advice on how to tune the injection controller. The only difference I have seen by forking out $550 so far is no more decell popping. Do I need a Dyno done?

Also, the Hcharger had pretty poor instructions and even worse photo descriptions for a layman, so I am not sure I even have that thing hooked up right. I was told by a MC mechanic buddy that if it wasn't hooked up right, the bike wouldn't run. I'm hearing a lot of air though and no noticeable HP increases.

Any advice would be greatly appreciated. XMich

[Chicago-Spike]

Adding a Hyper and gutting the stock pipe will not get you a lot of increase, if any at all. The Hyper is OK, better than stock, but not great there are better intakes than the Hypers. The stock pie gutted, as in nothing in there? you should have something in there for some backpressure or without some backpressure you will lose torque.
the WildThings unit has 3 pots you can adjust right? When others use a Cobra unit that uses the same tecnology their settings are in the area of 2-0-0.

[XMich]

2 years ago, I took the specs down (downloaded from this sight) to a metal fab shop to have the pipe done. There is a tube running down the middle of it. The WT Injection Controller has 4 pots. G,Y,R and RPM. After a lot of digging, I found a close adjustment (g2:45,y4:15,r2:00 and RPM4:00). This bike has the HCharger but VH pipes. We're dodging rain clouds here in Michigan. I haven't had to run the bike on those adjustments.

[aka]

Tapper - Great article.

I bought a used VTX 1800 on ebay - Great bike. Has after market pipes. How do I find out if it has PCIII or similar stuff that you mention in your article. Thanks.

[Chicago-Spike]

Tapper - Great article.

I bought a used VTX 1800 on ebay - Great bike. Has after market pipes. How do I find out if it has PCIII or similar stuff that you mention in your article. Thanks.
Look for any of these units under the seat or behind the side covers;
http://www.hondadirectlineusa.com/vtx/p ... =112073235 (http://www.hondadirectlineusa.com/vtx/product.asp?pid=4472&ID=112073235)
http://www.hondadirectlineusa.com/vtx/p ... =112073235 (http://www.hondadirectlineusa.com/vtx/product.asp?pid=2255&ID=112073235)
http://www.hondadirectlineusa.com/vtx/p ... =112073235 (http://www.hondadirectlineusa.com/vtx/product.asp?pid=464&ID=112073235)
http://www.hondadirectlineusa.com/vtx/p ... =112073235 (http://www.hondadirectlineusa.com/vtx/product.asp?pid=2828&ID=112073235)

[aka]

Thanks. Will look for it this weekend.

[VTXRydah]

I've heard people talk about 40+ MPG on the VTX1800... The MOST I'm able to get is around 110 miles on 3.5 gallons of gas (87 octane). I have a K&N air filter, stock exhaust, and do mostly highway riding. I spend most of my time in 4th gear, between 70 and 80 MPH, but attempting to run that same speed in 5th gear seemed to decrease my mileage (probably due to a loss of torque at the lower rpm). I'd appreciate any suggestions you guys can offer. Any ideas???

[Chicago-Spike]

I've heard people talk about 40+ MPG on the VTX1800... The MOST I'm able to get is around 110 miles on 3.5 gallons of gas (87 octane). I have a K&N air filter, stock exhaust, and do mostly highway riding. I spend most of my time in 4th gear, between 70 and 80 MPH, but attempting to run that same speed in 5th gear seemed to decrease my mileage (probably due to a loss of torque at the lower rpm). I'd appreciate any suggestions you guys can offer. Any ideas???
Cruising at 70 you should be in 5th, it drops the RPM using less fuel and better mileage. How many miles are on the engine?

[VTXRydah]

I've tried that. I could be way outta my tree, but to me it seemed that when I did that, I got even LESS mileage. I've found the rev-limiter cuts in at (or about) the following MPH

1st gear -- 30MPH
2nd gear -- 60MPH
3rd gear -- 80MPH
4th gear -- 120MPH
5th gear -- ?? (been to just shy of 140 already, but that is about as fast as I've gone. Anything faster than that, i have a sport bike to do)

With that in mind, I figured "tooling" along at 70 - 80 MPH in 4th gear would be fine, and I'd still have enough "punch" to get outta the way of the guy on the cell phone. I will try 5th gear again, however. Perhaps I was mistaken in the amount of miles I got to a tankfull of gas.

Another thing though... It seems when my reserve light comes on and I go to fill up, the tank only takes about 3 or so gallons of gas... With a 4.8 gallon tank (that can hold 4.5 gallons of gas, due to its design), and a .8 gallon reserve, I would expect about 3.7 to 3.8 gallons needed, when the light first comes (more if I stretch it, before filling up). Anyone else seeing this?

[VTXRydah]

Sorry Chicago-Spike. I didn't answer your question... My Phat Gurl has about 12000 miles on her.

[Slacker_Guy]

Nice job Tapper. While you are laid up, you should find a job as a tech writer. I am very impressed.

[VTXRydah]

I stand corrected... Chi-Spike, you are the man!!! I went on a trip last week from NJ, to OH. I was able to get the mileage everyone else is experiencing. On the PA Turnpike, I went 164.4 miles on 3.78 gallons of 87 octane. That comes out to 43.465 MPG!!! Sweeeeeeet!! Thanks again for the advice.

[c32077]

Thanks Tapper.

I posted a query on the tech board and was directed here by Morleyz. This is some awesome info. I had to print it all out to take with me to read at work. I didn't have time to read it all but I got my questions answered so I couldn't be happier.

Thanks again

Peace

[Apache]

Great post! I'm a relatively new visitor to this website and just found my way to your post. Thanks for taking the time to put it together.

I bought my 2002 VTX 1800C less than two months. I know virtually nothing about the bike and have been experiencing some problems with front cylinder plug fouling, exhaust popping and a few other things.

It came with a PC3 of which I know nothing about but have suspected it to be the cause of some problems I've been experiencing. I do not know how to re-map it so I have been considering removing it as I am not concerned about getting the highest performance possible from my bike. I just want a smooth running bike with the least amount of problems. Gas mileage better than 30mpg would also be great.

Your post has enlightened me on several concerns I've had including wether the PC3 is even needed and can be removed. I also had concerns about excessive decel popping. After I replaced the heavily carboned front cylinder plugs (replaced the rear also) the bike ran much better than when I bought it. It understandably had more power and minimal decel popping.

I was hesitant to remove the PC3 because I have Vance & Hines pipes and an aftermarket K&N air filter. After reading your post I am going to remove the PC3 today and see if things improve.

Thanks again for a well written and helpful article.
Jack

[phase1]

Thanks Tapper, great post.
Phase1

[cane corso]

Hi I'm new on this VTX sight . My VTx 1800 I got installed a dual intake as well as looking cool it realy woke my VTX even more. But I heard that I could instale a 2000 kit and put in high performance vales. I was woundering if any of you guys that done this kind of engine work? And if it made that big of a difference for the buck? And how much more HP and torque gained? And does the engine sound more throaty? Thanks Kevin

[cane corso]

XRIDERS great post. Sounds like you’re very knowledgeable. I was hoping for some good sound advice. I have a 2002 Honda VTX 1800 and I got installed a dual intake so now I have a intake on both sides of the bike with Cobra pipes. But I like the big tire look and would like to put a 280 or 300 tire on. I know the kits are $6,000.00 and I know I need to get a least a 3 degree triple tree to make it work. And I was thinking of doing the engine up a little more to have more torque and Hp, but I'm not sure if its all worth spending all that money on my VTX and getting a double knuckle u joint to fit a 280 tire or converting to a chain - will I have nothing but problems? Or am I better of getting a Suzuki M109R that is very similar as the VTX and I heard that I could put a 280 tire on that without any fabrications that there is enough room. Is there any comparison? Or am I better off spending the money on my VTX. I just see so many people even putting a 240 on their VTX and selling it. Is it because the VTX is not designed for a big tire? And I know the Suzuki has a 240 tire on it already. Would it handle better then the VTX because they spent money designing the bike to handle the wider tire? Does it matter? Or I was just thinking of getting a Triumph Rocket III that already as a 240 tire and a lot more torque and hp without even doing anything to it. If you can please help me out on this decision with all you experience I would really appreciate it. Thanks.
HAPPY NEW YEARS, Kevin

[benandjennifer]

thanks a lot man never been a gearhead but this article really helped me out a lot :D

[benandjennifer]

everyone i talked to said the m109r is awesome on takeoff/burnouts/wheelies ect.. but that it was one of the worst handling bikes ever in the twisties. no personal experience just word of mouth

[utahguyiam]

Thought I'd join in on the tapper butt kissing parade (which is well earned).

Tapper, I've now read this article, and your article on oil quality (from the tech site)... I've got to say... you are the best I've read. You have a way of communicating the entirety of a subject in a way enables someone with no technical knowledge to understand the concept. I knew literally NOTHING about oil, and after reading that article, I now understand that I've been making a huge mistake buying cheap oil for years, but more, I understand WHY that was a mistake.

I thank you, and all of my future cars and motorcycles thank you for the great information you've provided.

[Tapper]

Your gonna want to kiss something else. My ass looks like a ziplock baggie full of cottage cheese.

I mean really.

[Paps]

Dayam......... I cant believe I just got around to reading this. Good stuff dude...................

[BiGDoG96]

Your gonna want to kiss something else. My ass looks like a ziplock baggie full of cottage cheese.

I mean really.

Now see... I'm pretty sure we all could have gone living full happy lives without ever knowing that.

On a more positive note... great article and a facinating read. I'm not a wrench head but more of a computer geek and I thoroughly enjoyed the write up.

[troyw]

Great article Tapper.
However, it seems like you're saying that units like the Cobra Fi2000R
are just a total waste? So, I just totally wasted my money?
It seems to be running well, and gas mpg is very good, but the end caps
on my Speedster Longs get dark quickly. Maybe too rich then...I don't know.
It seems to have good power, except a little more shy on the bottom, maybe
because of the pipes. I read a review of the Cobra Speedsters that cited
a little loss in the 1500-2500 rev range, but gains elswhere.
I'm just curious at how, if the Cobra Fi2000R isn't a total loss, the settings
of 2-0-0 were arrived at by some folks? If the setting is zero, that's not
doing anything, so an optimum F/A ratio won't then be attained, right?
Am I understanding everything in your excellent write up?

Thanks!

[Chicago-Spike]

Great article Tapper.
However, it seems like you're saying that units like the Cobra Fi2000R
are just a total waste? So, I just totally wasted my money?
It seems to be running well, and gas mpg is very good, but the end caps
on my Speedster Longs get dark quickly. Maybe too rich then...I don't know.
It seems to have good power, except a little more shy on the bottom, maybe
because of the pipes. I read a review of the Cobra Speedsters that cited
a little loss in the 1500-2500 rev range, but gains elswhere.
I'm just curious at how, if the Cobra Fi2000R isn't a total loss, the settings
of 2-0-0 were arrived at by some folks? If the setting is zero, that's not
doing anything, so an optimum F/A ratio won't then be attained, right?
Am I understanding everything in your excellent write up?

Thanks!

The Cobra only adds fuel, yes. And as the VTX runs rich at the mid and upper RPM range, the settings of zero for the mid and upper RPM range is correct. No need to add fuel if it is already running rich

[troyw]

Yes, you're right, and I've got mine set at about that...AND it's running
really, reallllllyyy well. BUT, it was set too rich from Honda with stock
filter and stock exhaust. If a high flowing exhaust and higher flowing
air filter are added, that would even that out a bit, wouldn't it?
What I was just wondering is how do you know those lower settings
are actually working with the pipes & filter unless it is dyno'd to get the
A/F ratio? We're actually just guessing...though a pretty good one
considering that the bike with the settings at 2.5-.5-0 exhibits no lean
surging whatsoever, which is where I now have it set. I just keep going
down to see when it actually will lean out, and it doesn't appear too.
So, we're making an educated guess, but I'm just curious if you've seen
an actual dyno result. I'd be curious to see the actual numbers.

All that said, I think you may well be right, and I wonder how Cobra, who
designed it and should know the best, set it rich like they did.

[jamieavtx]

Just want to chime in with my thank-you for such an informative article.
I just bought an 05 F and now have a base of knowledge to start planning my mods around.

Cheers,
Jamie.

[IRONBUTTX]

Excellent read but shouldn't you be working on your bike :lol: What ever came of the ins. B.S.? Did they pay up?
Clif

Tapper:

Thanks for am informative article. I almost didn't read it, thinking it might be 4-stroke 101. But I learned alot!

Thanks,
IBTX

[tnvnl]

Great read!
My only thing is this, the "backfire" you mention from the unburned fuel being forced into the exhaust is not actually called "backfire".
Its called "afterfire" ( Honda term). an honest to goodness "backfire" is usually caused from pre-ignition while the intake valve is open, and the fuel charge burns back into the carb/intake, and blows those cool flames out the intake.

[dirtusmvm/c]

Does anyone know of an aftermarket fuel tank for a 2003 1800 retro? 5 gal or larger would be nice.

[Chicago-Spike]

Does anyone know of an aftermarket fuel tank for a 2003 1800 retro? 5 gal or larger would be nice.
No such animal, you have to get someone to modify your stock tank(cut&weld&pressure test )

[sacred_dog]

when I am watching television and I back fire in front of the tv, I insist that it is simply "windtalking" in the most patriotic of terms.

[SmoothJyzz]

New VTX owner...got a 03 C about two months ago with 3K. It has 6K on it now. I struggled with the airbox F/M pipes question as I'm a computer guy, not a mechanical guy.

I went in and got a FuelPak from V&H to go with the Kury Air cleaner and V&H Staggered pipes. I wish I'd have read this article before hand. 1.) the information about WHY I was getting it is priceless. 2.) I'd have realized I didn't need the FuelPak, and 3) the research would have not allowed me to buy the damn FuelPak as, contrary to what's in the catalog at BikersBay, it's not for the 03 VTX1800..starts at 06+.

Now, if I understand that treatise on exhausts, fuel etc, it must be the best explanation I've come across yet.

Kudo's to the author, you really should submit that to a magazine...it would likely help ALOT of people.


daryl :orac:

[AZVTX'er]

Hey Tapper, I'm a noob to the VTXOA but an oldie to the VTX. Had the 1300R for 2 years and just graduated to an 1800N. The information I've gotten from every motorcycle mechanic I could get my hands on (including the honda dealership) is OMG don't run aftermarket exhaust or a Baron BAK without doing one of the fuel managers. You'll overheat your motor, overheat and bend/warp/break exhaust valves and blow up your motor. Are you saying all of these people are just full of it? If I can get away from changing to a fuel manager I would be in my optimum ZEN in life as I love my stock settings/power/etc. I hate the way my bike sounds stock (like an electric motorcycle) and I really dig the Baron BAK look and would like to get rid of the stock plasti-chrome/plastic beastly intake. I have a BAK on order and my Cobra Speedster slashdowns will be here on Monday. I guess my real question here is will I do any damage long term or short to my engine w/o that fuel manager? What are your thoughts?

[Chicago-Spike]

Hey Tapper, I'm a noob to the VTXOA but an oldie to the VTX. Had the 1300R for 2 years and just graduated to an 1800N. The information I've gotten from every motorcycle mechanic I could get my hands on (including the honda dealership) is OMG don't run aftermarket exhaust or a Baron BAK without doing one of the fuel managers. You'll overheat your motor, overheat and bend/warp/break exhaust valves and blow up your motor. Are you saying all of these people are just full of it? If I can get away from changing to a fuel manager I would be in my optimum ZEN in life as I love my stock settings/power/etc. I hate the way my bike sounds stock (like an electric motorcycle) and I really dig the Baron BAK look and would like to get rid of the stock plasti-chrome/plastic beastly intake. I have a BAK on order and my Cobra Speedster slashdowns will be here on Monday. I guess my real question here is will I do any damage long term or short to my engine w/o that fuel manager? What are your thoughts?
As it says, you CAN run pipes and airbox without doing harm. Thousands here run pipes and airboxes, many of them have for YEARS, without a fuel manager and have no adverse effects from doing so. Put the pipes and airbox on, while you do this you should also remove the pair system(anti-smog device ) as this will help with keeping the decell popping down. See how to remove it here, www.bareasschoppers.com/desmog (http://www.bareasschoppers.com/desmog)

[Chicago-Spike]

Welcome to the board!
Bookmark or save to your favorites folder, these websites, http://tech.vtxoa.com This is the VTXOA Garage, a sister site to this message board and contains all your How-to/Tips/Tricks/Why’s and links to other helpful sites for your new VTX. http://www.bareasschoppers.com/ A fellow VTX Riders site that has many write-ups on “How-To” do work on the VTX. Also, for you 1300 guys http://vtx1300tips.com/VTX1300TIPS.htm another fellow VTX Riders site.

There is also a helpful Search icon at the top of every page
Search Query section
Search for Key Words;__________________________

Below that click on the "Search for All Terms" button, effectively unchecking the default selection of "Search for any terms or use query as entered"


Search Options section
Select 1, and only 1 "Forum" to search in at a time, or at all.
For example, "Best airbox" I would only search in the "1800 Tech Board"



That's the basic way, you can limit further by using some of the other "Drop-Down" menu's like if you know the thread you are looking for is only a week or so old, etc....

Now that you have a list of threads you've searched for, do not just click on the thread you want to read. Instead RIGHT click on the thread and select "Open in New Window" This will pop up a new window with that thread in it, leaving your searched list intact for you to go back to.

The purpose of the "Search" is to offer a member the opportunity to research his/her question better. There is so much information from past threads that you may never see because that member is no longer here, or doesn't see your new post, or just won't respond to the same question. So use it to your advantage and enjoy the board! View this funny and informative film about posting and searching…
http://uploads.ungrounded.net/188000/188612_Posting.swf

Take a few minutes to familiarize yourself with the forum. At the top of every board there are threads that are tagged as "Sticky" These threads are "Sticky" because they contain very important/valuable information about the VTX and everyone should read them.
The thread at the top of the 1800 tech board called, "Air, Fuel, Motors..." will answer most of the performance questions...
viewtopic.php?t=28918 (http://www.vtxoa.com/forums/viewtopic.php?t=28918)

Also, update your Profile to include where you live and what type X you have to your Signature line. I.E. 1300/1800/C/F/N/R/S.

[mark_1bx]

Hey Tapper, I'm a noob to the VTXOA but an oldie to the VTX. Had the 1300R for 2 years and just graduated to an 1800N. The information I've gotten from every motorcycle mechanic I could get my hands on (including the honda dealership) is OMG don't run aftermarket exhaust or a Baron BAK without doing one of the fuel managers. You'll overheat your motor, overheat and bend/warp/break exhaust valves and blow up your motor. Are you saying all of these people are just full of it? If I can get away from changing to a fuel manager I would be in my optimum ZEN in life as I love my stock settings/power/etc. I hate the way my bike sounds stock (like an electric motorcycle) and I really dig the Baron BAK look and would like to get rid of the stock plasti-chrome/plastic beastly intake. I have a BAK on order and my Cobra Speedster slashdowns will be here on Monday. I guess my real question here is will I do any damage long term or short to my engine w/o that fuel manager? What are your thoughts?



Hey welcome to the board! :beer3:

[wanderingbear]

I was taught in the service to call the ignition an event, so to the engine has 2 strokes an event and 2 strokes. It's the same thing you said just thought I'd share military jargon. I was trained on reciprocating radials, jets and jet helicopters. I ran the engine shop after Nam until I was done doing my time. I served all 6 years active and enjoyed it. I went to the Navy schools but I was a Marine. Great article I know we all took something away with us for reading it. You should of heard the old Pratt & Whitney's pop with those massive wide open tube. Once again fine jobs thank you.

[Red Chicky]

This was a great read! I just got a used 2006 VTX1300S and, while the outside is immaculate, the bike has very little power or zip. It has 4,000 miles on it and I bought it at a H-D stealership that refused to do anything to the bike prior to sale because it was not a H-D, hence, I bought it "as is". It idles fine. I don't use the choke to start it...I give it one good twist of the throttle and release it then hit the starter switch. Starts fine. The oil is old and black. The exhaust smells and I can smell it even going 50 mph. The top muffler pipe is real hot as I ride. I am taking it to a mechanic on Tuesday but do any of you have any ideas as to what may be wrong or is it just way over due for a tune-up and its "first" 600 mile check-up since I believe this bike has never had any mechanical maintenance? An old lady could walk faster than this bike can move. It simply has little power. What do y'all think? :dontknow:

[GaryH NC]

This was a great read! I just got a used 2006 VTX1300S and, while the outside is immaculate, the bike has very little power or zip. It has 4,000 miles on it and I bought it at a H-D stealership that refused to do anything to the bike prior to sale because it was not a H-D, hence, I bought it "as is". It idles fine. I don't use the choke to start it...I give it one good twist of the throttle and release it then hit the starter switch. Starts fine. The oil is old and black. The exhaust smells and I can smell it even going 50 mph. The top muffler pipe is real hot as I ride. I am taking it to a mechanic on Tuesday but do any of you have any ideas as to what may be wrong or is it just way over due for a tune-up and its "first" 600 mile check-up since I believe this bike has never had any mechanical maintenance? An old lady could walk faster than this bike can move. It simply has little power. What do y'all think? :dontknow:

Hope your not going to a dealer..or someone not familiar with the X...

Sent ya a PM

[Red Chicky]

Yes, I thought a great deal about where to take it. At the stealers, you might get a good mechanic or you could get someone with 2 hours experience. Since you live here in N.C., you are probably familiar with Scootworks which is up in Zebulon. I took my Aero 750 there last year for a lot of custom work and they did a wonderful job and were very knowledgeable. I called them Friday and explained everything to them and they told me what they were going to do and how much it would cost. ($380.00) for everything. He will go over everything and won't stop until he finds out what is wrong and then they will show you the problem. But I still hate not knowing at this point because I would like to ride but I won't do it until I know all is well. Thank you for your response. C'mon guys....anyone else have any ideas? :dontknow:

[Chicago-Spike]

The person that wrote the first post, has not been here for over 2 years. Post your question on the 1300 board for more responses, this board is more for putting "How To;Step-by-Step" write-ups on here. Not questions ;)

[Vman8r]

Well that was definitely an informative little piece of work! Thanks Tapper! Now on top of being annoyed at the backfiring and popping sound coming out of my bike, I get to be conflicted about it's usefulness to the environment, etc. I don't really care about it, as long as it's "normal". However, I was thinking of going to a K&N airfilter and wondered what your thoughts might be about that? I've heard they don't really add that much horsepower, and they allow more dirt to get inside the motor than the stock filters do. So I'm torn...I want to get more mpgs, if it means more horses then so be it! I have a stock exhaust system, and a super loud pipe called a Sideburner. I went back to the stock pipe cuz I felt my right ear drum actually rattle at certain speeds with the other pipe on...very painfull! I would like to know if there's a way to take the stock exhaust and make it a little louder without making it sound like there's an air leak somewhere. I drilled some holes in the ends of my stock pipes, and it sounded sick...so I plugged them with self threading screws. Now I'm back to square one.
I might also add, that since I took my tank off the bike, I've been having a bit of trouble cold starting. As long as the bike is warm, or has been ridden that day, it starts without a problem. But left over night, it has to be dialed in just right with that little adjustment knob between the two cylinders, or it won't start. It likes more fuel, but trying to do it with the throttle doesn't work, just the knob. I might also add my air filter is very dirty and I'm getting a new one on Monday, I'm hoping that will solve the problem, but we shall see!