How to calculate flywheel horsepower from RWHP - Ford Mustang Forum
 
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post #1 of 12 (permalink) Old 02-21-2009 Thread Starter
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How to calculate flywheel horsepower from RWHP

Is there a good way to estimate what your HP at he flywheel would be if you know your HP at the rear wheels? On my gt with and automatic and 3.31 gears.


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post #2 of 12 (permalink) Old 02-21-2009
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For an auto divide your RWHP by .85 and that will get you close.


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post #3 of 12 (permalink) Old 02-21-2009 Thread Starter
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OK thanks Ipulled a 290.52 on the dyno today so I guess the flywheel HP would be about 342?

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post #4 of 12 (permalink) Old 02-21-2009
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What is it for a manual tranny?

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post #5 of 12 (permalink) Old 02-21-2009
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If your trying to find your flywheel hp, and you know your rwhp say 400 divide the 400 by .85, and your flywheel hp would be 470.588. And if you know your flywheel hp, and want to know your rwhp you would multiply say a stock S197 @ 300hp by .85 and you would come up with 255 rwhp. That formula, is usually pretty accurate with a stick or automatic, Mike. SCT Tuner.

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post #6 of 12 (permalink) Old 02-21-2009
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People will debate it but the variance between auto and stick is "usually" around 2 to 3%. Nothing major.

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post #7 of 12 (permalink) Old 02-22-2009
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Quote:
Originally Posted by PLstang View Post
People will debate it but the variance between auto and stick is "usually" around 2 to 3%. Nothing major.
I agree because at the track there is not much differance. I have raced S197`s with the similar mods and have won. I raced one guy who had a manual trans and he had long tube headers when I did not and still beat him. I know that it was all in my tune. His tune was not as good.

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post #8 of 12 (permalink) Old 02-22-2009
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Quote:
Originally Posted by 04KenneBellGT View Post
What is it for a manual tranny?
You generally lose about 15% for an auto and 12% for a manual from the flywheel to the rear wheels. Just a general rule of thumb though, not exact.

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post #9 of 12 (permalink) Old 02-22-2009
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Why would you care what your FWHP is?

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Quote:
Originally Posted by Herknav View Post
Why would you care what your FWHP is?
My guess is someone asked him how it compares to the "what ever car" in horse power. Since new vehicles are rated at the flywheel not the rear wheel he can give them a more accurate comparison. That's just a guess.

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740RWHP/motor 904RWHP/spray
9.01 @ 152 mph 1/4 mile, 1.40 60'
2008 Clash of the Titans World Finals Champion
2009 Strictly Street Points leader/ET & MPH Record Holder

2009 GT500 Grabber Orange Vert 594 RWHP
11.5 @ 120mph it's my slow car!
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in other words, who's got the biggest wang...

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post #12 of 12 (permalink) Old 02-22-2009 Thread Starter
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Plstang is right to a point but it is mostly just me wondering. Since most every add you see state fwhp I wondered about what mine was. As far as the biggest wang.....it looks like that one in the middle of the monkeys face is the hands down winner.

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