I just want to figure out my flywheel HP from my future dyno testing.
One of the HP calculators gave me 208 RWHP and 260 FWHP with 20% drivetrain loss,
and 208 RWHP and 231 FWHP with 10% loss.

Thanks,

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WS6 Trans Am.

View My Ride @ thirdgen.org

 

I thought it was around 15% for stick and 18-22% for an auto.

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I read it's about 10% for manuals and about 14% for autos.

Jason

 

Cool, thanks

 

Holley has said that their dyno tests have shown 17-18 for a manual and 20-22 for an auto.

 

When I was at the chassis dyno place the other day, the guy who owned it (circle-track guy - on average, those seem to have about twice as much on the ball as your typical drag racer) was telling me that he has a friend who owns an engine dyno. On numerous occasions, people have taken their motors there, and had them tested; then dropped them in their chassis and brought them to his place. He says that the smallest difference he has ever seen between the 2 readings was 16%; that was in a sprint car with a Powerglide with a metallic drive (no torque converter) and of course open headers. He says that street cars usually put up numbers more like 22-25% different; and that the auto cars and the stick cars don't differ by a very great ampunt in how much lower they read on his than they do on the other one.

There are way too many variables between how an engine runs on the dyno and how it runs in the chassis for the "loss" number to be meaningful. For example, on an engine dyno, there's usually no smog pump, no cooling fan, no alternator, & no power steering; there's an almost unlimited supply of cool fresh air; there's a far better flowing exhaust than exists in most cars; and so on.

So it's really mostly meaningless to talk about "drivetrain loss" that way, it's not the whole real world story at all. That is, the RW number is what counts, since that's the only way you ever get to use it; any calculation of the crank number from the RW numbers is just a wild guess in most cases.

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