measuring torque on a dyno

[G_A_V]

Hey guys, I was wondering when measuring kw on a dyno you add a few to work out what it is at the engine, but what about torque, because i have seen ridiculas amounts of torque above the factory beeing pulled out on a dyno, do you remove a few nm or what ??

[smorison]

wow ...
for once i dunno..............


see what i can find

[smorison]

http://www.car-videos.com/articles/hors ... torque.asp

[ruchi]

That link Steve provided is very good.

G_A_V what you are refering to is the difference between power "at the wheels" (tyres) and power "at the flywheel" (engine). The difference between these two is calculated based on the gear ratios of the car with allowances for drivetrain loss.

It is worth noting that most dynos measure torque at the wheels - i.e. they measure the ability for the tyres to turn the drum on the dyno. Then using the calculation listed in Steve's link, they also plot the power (KW) of the car. Then using the gear ratio and drive train loss calculations they can work out figures for the engine.

So the only thing that is actually "measured" is torque, everything else is "calculated" and with any calculation it is subject to some errors. If there is any wheel slippage then the calculations will be wrong, likewise it is very easy to introduce errors with the gear ratio and drive train loss calculations, therefore the calculations for engine power and engine torque can easily be wrong.