just like the thread title says i'm trying to figure out how to figure out the engines flywheel horsepower after a dyno pull which shows rear wheel horsepower ........what type of calculation is it to try and figure this out

What tranny and converter are you running? different combos use different percentages of horsepower.

What tranny and converter are you running? different combos use different percentages of horsepower.

this is on our dirt track dwarf car with a yamaha R1 and a toyota 10 bolt axle running 4.10 gears

but also interested in what the calculation is for a car with either a manual or automatic

usualy a safe bet is engine HP -15% = RWHP.

so take your RWHP. and add untill the number you get - 15% = your RWHP.

15% is a general amount.. always figure less loss for a manual.. more loss for an auto. it can be between 12%-20% loss.

that is for a car.

for a motorcycle engine i wouldnt even guess 8% loss.. maybe less. depending on how your setup is.

i agree. 12%-20%. it is a very general range though. deeper,,, or read as "optimized" 1/4mile gearing will get you there slightly quicker with slightly less hp at the flywheel.

so it would be kind of a guess type figure from there if it's not geared to rpm at arround 200-500 rpms over the cams advertized peak rpm at the finish line. that's typically where the best numbers show up,, when geared that way,, if you can hook it on the launch. hope it helps.
andy

Here's how to calculate your flywheel power from your chassis dyno chart:

1. Read peak power from the chassis dyno chart.
2. Divide this by your most optimistic engine power estimate
3. Multiply this number by 100
4. The result will be your drivetrain loss in %.

onovakind- you're killing me, man!

250HP at the rear wheels divided by 500 (most optimistic engine power estimate) then multiply the result by 100 = 50% drivetrain loss.

I love it! Best of all, it works perfectly every single time! Heh heh heh.

"Yeah, my engine makes 500HP but the damned drivetrain is eating half of it." Too funny.