horsepower measured @ rear wheel conversion?

[Anonymous]

Is there a formula to convert horsepower @ rear wheel to horse power @ flywheel? Also, what is the relationship between the two?...Sorry if this is a dumb question my manual only has stock numbers @ flywheel I had the bike dynoed and the numbers are @ the rear wheel and are about 20% lower. Does that sound right?

[Anonymous]

Usually, the difference is 10-15%. Where the dyno figures corrected to sea level?

[Anonymous]

The dyno shop is less than 100 feet above sea level.

[Anonymous]

I wonder if the figures that are given to us by the manufacturers are not somehow exagerated?? Or at least gotten from one out of((N)) machines that were tested on the same day. And of course dont forget the state of tune of your of your bike. Mileage etc.

[cbxchris]

Just for a example because I have lots of experience with them. On a hayabusa the factory claims 172 at the crank....they usually dyno at around 150-155 stock at the rear wheel With a good pipe/injection remap,filter and airbox mod you can get 165-170 tops.

[Anonymous]

Also depends upon where on the rpm scale the maximum horsepower is rated. Compression, timing, plug gap and the engine's ability to breath IE intake and exhaust play a lot in the horsepower numbers. Carboned up exhausts restrict flow, air boxes inhibit intake flow and so forth. I am sure that manufacturers measure hp with new clean engines, clean exhausts and clean air filters.