Dyno Figures

[Demolition49]

My mate got his bike tested on the weekend on a dyno and said it came out at 90 hp, hes meant to have 107...

I said was the figure at the wheel or flywheel....

 

he then said at the flywheel, I said that seems a little low for your bike etc...

 

But before I could discuss any more a colleague of mine said NO, all European vehicles are quoted HP at the wheel. I said that's not the case but hes like only the Americans quote the actual HP of the engine... so back me up guys here, i need to get my argument straight before i go telling him hes not right, or am I wrong?

 

I always thought that manufacturers quote the HP at the flywheel and on a dyno you get both figures for wheel horsepower and an estimate of the flywheel HP over like 3 runs or so?

[Chris`I]

Manufacturers quote flywheel - or more importantly - engine HP, which they will get from strapping the engine to an engine dyno (ie completely out of a car).

 

Dyno centres can have varying setups. Some can dyno the engine, but means taking it out of the car, that will get you true engine HP. Most have rollers, where you strap the car down. This measures torque (not HP) at the rollers and interpolates power at the wheels and also can calculate the transmission losses and estimate flywheel HP. This is a guess though. Similarly hub dynos measure torque at the hub and interpolates power and can also guess at flywheel power.

 

 

Should also be noted that ramair effect does work quite well on superbikes. If they have a ramair intake system, a normal dyno fan will not generate the required airflow and pressure for this to work properly. This means he will lose top end on the dyno as its not the same as the open road. Not quite the same on a car as the effect isnt anywhere near as profound (not sure it even works on cars)