NviouSS

iTrader: (8)

anyone know how to convert it?

BADSZ28

iTrader: (39)

Well RWHP is after a 15-20% loss. So I would do this.

RWHP/80-85%=FWHP/100

So

FWHP=(RWHP*100)/80-85

or

FWHP=RWHP/.80-.85

jrp

iTrader: (16)

add ~15% to your RWHP

slyws6

Typically M6's cars consume 15-18% power loss through the drivetrain and A4's 18-22%. Going based on the assumption of M6=15% loss and A4=20% loss you would do the following

For M6: (RWHP * 100) / 85 = FWHP
For A4: (RWHP * 100) / 80 = FWHP

-Sly

NviouSS

iTrader: (8)

if i divide by .85 i get 436.47 hp
if i divide by .8 i get 463.75 hp

doing it this way i get 426.65 hp

jrp

iTrader: (16)

how much rwhp are you putting down ~365?

NviouSS

iTrader: (8)

371 hp

HitmanLSX

Doing it this way means you're adding 15% of your rwhp number which in reality rwhp is 85% of fwhp. so you want to divide rwhp by .85 like was mentioned earlier for an M6 car, A4 I'd say .80-.75.

Since your drivetrain loss is 15% of fwhp not 15% of rwhp.

I think I explained that right.

slyws6

Correct, if you do it like the way I mentioned it will get you right on the money. Thus you have 436.47 FWHP

-Sly

hugger1975

iTrader: (3)

I was told that changing gears also takes a higher %

like my 373's should avg 18% loss.


any truth to this?

slyws6

Yes, I wouldn't expect another 3% loss with 3.73's. Maybe 1-2% at most. I would expect 3% with 4.10's.

-Sly

PRAY HRD

iTrader: (119)

magazine testing usually use's a 12% loss for a manual tranny and a 17% loss for a 3 speed auto. now for a powerglide, it's probably closer to what a munual loses.

400rwhp...manual.....454.55 fwhp at 12% loss.

400rwhp...auto.......481.93 fwhp at 17% loss.

math formula with a calculator is xxxrwhp / .88 for manual and .83 for auto.

of course, this is just an avg. for an easy estimate. there are many other variables to it and therefor no way of getting an Exact figure. driveshaft weight, rear wheel weight, rear axle weight.....see the trend? the more rotating weight you can take out of the car after the flywheel, the less power it will rob and thus alters the calculation considerably. hope that helps.

later,
Dave

Race Car Driver

Which is one of the reasons engine builders prefer to use engine dynos/numbers. The results are much more predictable.

PRAY HRD

iTrader: (119)

exactly. however if an engine is already in a car, obviously you have to use a chassis dyno if you're not willing to pull the motor to find out. either way, both methods have their advantages.

Dave