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Discussion Starter #1
Good day everyone.

I had my bike dyno'd yesterday here in Albuquerque. My bike runs and sounds great, but confused with the numbers of the dyno results. This is my 3rd VTX 1800 and all of them have been modified and ran better after doing the same mods. I have done the desmog, put a MTC clutch, Thunder Hurricane air intake, Freedom Performance Sharp Radius Curve exhaust and PCV.

According to the dyno result, my bike started at 78.74 HP and 95.50 TQ.
After tuning: 85.46 HP and 101.92 TQ.

The beginning numbers appear way off what others have reported. Any ideas what could be going on here. My bike runs and sound great after the tuning and there was nearly a 7 HP and 6.5 TQ increase after tuning. Could the elevation and temp have anything to do with it?

Thanks in advance for your input.

seb
172754
Dyno sheet 05-15-2020 b.jpeg
 

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I would guess the exhaust as the major culprit. The VTX likes backpressure and those type of short pipes just don't make a whole lot. The elevation and temp and humidity do play a large part as well. The higher you go, the less power you make because of less o2 in the air for the engine to use.
 

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3 horsepower per 1,000 feet for normally aspirated engine. generally
 
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Discussion Starter #4
I would guess the exhaust as the major culprit. The VTX likes backpressure and those type of short pipes just don't make a whole lot. The elevation and temp and humidity do play a large part as well. The higher you go, the less power you make because of less o2 in the air for the engine to use.
Thanks for the info, Spike
 

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3 horsepower per 1,000 feet for normally aspirated engine. generally
Thanks for the info, Chuck. By this reasoning, my bike would be near 102 RWHP (unknown TQ) at Sea Level, since I am at 5300' here. Can't wait until I visit my daughter in Tallahassee :devilish::devilish:
 

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air pressure at sea level is 14.7 psi
air pressure at 5,000 feet is 12.23 psi.
air is thinner and has less pressure.. = less horsepower.

 
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There's another thing to remember in all of this. There are people who know how to use their Dyno and there are people who know how to make the numbers bigger than they should be. There are compensation values that can be entered to allow for altitude, humidity, and ambient air temp. Some Dyno operators will adjust the numbers to read as if they were run at sea level on a cool day. Others will choose to give you the numbers the bike ran, right there and then. So as mentioned, had your run happened at sea level on a cool day, likely your numbers would be more in line with your expectations.

The message here is that, if the bike runs well, and is not down on power, by your estimation, then the Dyno is just a relative number anyway. It gives you a baseline from your starting point, to a final solution. You know what you gained, and that's the important number. My Dyno runs had a AF chart as well, start and finish, and the object was not just a highest horsepower number, but a flat AF curve as well. A Dyno operator will tell you that they can make the final numbers anything you want them to be. The curve won't change, but it can be shifted.
 

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adjustable correction factors... :)... to display anyway the operator wants .
compare A to B... on same engine...
no other comparison .
 

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Nice job SWS!
Brought back memories of Cliff Randall's Chromeless Cruiser in 2003
 
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Thank you all for taking the time to respond. Good information. My "seat of my pants dyno" tells me that she is a screaming machine...and I like it.
She is! The numbers are just a small part of that story. Ride safe and enjoy the hell out of her! Just the therapy this stupid virus needs.
 
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Discussion Starter #14
What type daylight bracket is that?

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jellerolandboot, I am guessing you are referring to the driving lights. I am not sure what brand they are as they were already on the bike when I bought it. They were chrome, but I had them powdercoated gloss black
 

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Those ribbons fake cooling. Thought you can remove them

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On the VTX 1300, the fins around the heads can be removed. They are largely just for appearance. The 1800 the cooling fins are all real and assist in cooling that bad boy.
 
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On the VTX 1300, the fins around the heads can be removed. They are largely just for appearance. The 1800 the cooling fins are all real and assist in cooling that bad boy.
Interesting...I didn't know that. I have only owned the 1800...4 of them
 
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