how to convert rwhp to flywheel hp?
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Joined: Sep 2003
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From: "Tr"Asheville
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
For M6: (RWHP * 100) / 85 = FWHP
For A4: (RWHP * 100) / 80 = FWHP
-Sly
Originally Posted by BADSZ28
FWHP=RWHP/.80-.85
if i divide by .8 i get 463.75 hp
Originally Posted by jrp
add ~15% to your RWHP
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From: Lynnwood, WA
Originally Posted by jrp
add ~15% to your RWHP
Since your drivetrain loss is 15% of fwhp not 15% of rwhp.
I think I explained that right.
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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
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
Originally Posted by bickelfirebird
Which is one of the reasons engine builders prefer to use engine dynos/numbers. The results are much more predictable.
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
