Air, Fuel, Motors, and missives. Article. (Updated 1/3/06) - Page 2 - VTXOA
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post #11 of 25 (permalink) Old 09-01-2004, 07:35 PM Thread Starter
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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.

Yeah, that Tapper. Everywhere I go, there I am.
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post #12 of 25 (permalink) Old 09-13-2004, 02:08 AM
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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

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post #13 of 25 (permalink) Old 09-15-2004, 06:53 PM Thread Starter
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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.

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post #14 of 25 (permalink) Old 09-19-2004, 11:12 PM
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De Tuning Hell / Starved More Like it

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.
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post #15 of 25 (permalink) Old 09-20-2004, 12:34 AM
 
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De Tuning Hell / Starved More Like it

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?
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post #16 of 25 (permalink) Old 09-21-2004, 12:32 PM Thread Starter
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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.

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post #17 of 25 (permalink) Old 09-21-2004, 06:28 PM Thread Starter
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Re: De Tuning Hell / Starved More Like it

Quote:
Originally Posted by 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.

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.

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post #18 of 25 (permalink) Old 10-09-2004, 09:29 PM
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Re: De Tuning Hell / Starved More Like it

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
post #19 of 25 (permalink) Old 10-10-2004, 10:45 PM Thread Starter
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Re: De Tuning Hell / Starved More Like it

Quote:
Originally Posted by JPVTX1800
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.

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post #20 of 25 (permalink) Old 10-12-2004, 09:41 PM
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Re: De Tuning Hell / Starved More Like it

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.
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