calculating flywheel from rearwheel HP
 

RWHP Flywheel
276.6 359.6 76.9240% +1z
251.8 327.3 76.9217% -1z
12.42253022 16.15195737 1.13133E-05 Dyno RWHP Flywheel
264.2 343.5 76.922822% 279 362.7
257.98 335.37 76.9240% 278.192 361.7
260.32 338.42 76.9222%
274.16 356.41 76.9226% 272.3861 354.1
279.07 362.79 76.9233% 267.5 347.8
277.87 361.24 76.9212% 267 347.1
262.91 341.79 76.9215%
259.31 337.1 76.9238%
241.98 314.57 76.9241%

Rear Wheel HP (RWHP) / 76.922822 % = flywheel HP

i got it from http://www.onlineconversion.com/horsepower.htm caculations done w Gtech pro competition provided 1/4 mi times ( NOT Gtech pro competition HP calcs.).

column 1 = RWHP from Online Conversions site; column 2 = flywheel HP from Online Conversions site; col. 3 = % calculated from former; column 4 = dyno measured HP; col. 5 = calc flywheel HP

My question is does the 76.922822 % seem reasonable?

RE: calculating flywheel from rearwheel HP
 

That thing is way off for flywheel #'s

Manual: BHP = RWHP X 1+(Altitude X .00003) X 1.15
Automatic: BHP = RWHP X 1+(Altitude X .00003) X 1.22

So no, that does not seem reasonable, too many variables, that calculator is crap.

RE: calculating flywheel from rearwheel HP
 

Tik_Tok is correct. Don't rely on bcc333's calculation unless you just want to build up your numbers.

RE: calculating flywheel from rearwheel HP
 

edit

RE: calculating flywheel from rearwheel HP
 

You know, MustangForums has this wonderful thing called private messaging... just so you know.

RE: calculating flywheel from rearwheel HP
 

ok, Tic_Tok and GTRacing are more right.

I called Chris at Dynojet and explained the situation. I asked if there was a mathematical formula they used to calculate BHP (Flywheel) from measured RWHP on Dynojet. He said emphatically NO. He went on to say there are just too many variables (e.g., torque of drive shaft, etc. etc.) to realistically measure. He said I could pull the engine and put it on an engine dyno and get pretty close.

we went on to discuss and he suggested a very rough rule of thumb would be a very efficient engine/drive train would lose 12% a less efficient Mustang would lose 20%. He believes that the 2005+ automatic transmission probably is in the 15%-17% range of loss of HP BHP to RWHP.

therefore:
%------- BHP------ RWHP
88%---- 316.6---- 278.6
85%---- 327.8---- 278.6
83%---- 335.7---- 278.6
80%---- 348.3---- 278.6