If Im making 181 @ rear wheel

GS TRV · 10-10-2011, 04:17 AM

then what is it @ the crank??

Got my dyno run after PCV, full Akra & Pipercross filter. 8bhp gain with PCV & filter on std bike with exhaust alone.

T

GhastlyTT · 10-10-2011, 04:26 AM

If u take the 8hp as a % of whp, then you're making about 9 additional crank. So i'd bet about 202bhp.

fatbob · 10-10-2011, 08:32 AM

doesnt that make it 1 bhp down from standard

crabman · 10-10-2011, 03:17 PM

Factory rating is 193hp at the crank

GS TRV · 10-10-2011, 06:08 PM

who believes factory figures??

surely the best way is to use the same dyno each time and look for gains?

RansomT · 10-10-2011, 07:49 PM

If I was guessing .... Drive train loss is somewhere close to 8%.

yzfr1mike · 10-10-2011, 08:51 PM

In my engineering classes the rule was that a straight cut gear set has an efficiency of about 97%. The motor in our bikes consists of a primary gear set, a transmission gear set, and a chain drive. Chain drive efficiency was slightly worse than a gear set, so about 96%. (assuming a perfect chain and sprocket set that was well lubricated.)

Using this data, the overall efficiency of the drive train on our bikes is:

one X 0.97 X 0.97 X 0.96 = 90.03% Call it a loss of 10% due to the power absorbed by the drive components of our bikes.

I hope this clarifies the question of the rear wheel vs crankshaft power.

Mike