Thread: BHP from a dyno...

I suspect I am no better informed than you, however I would say that in theory the BHP and torque reading on a dyno should be the same. The ratios affect the ability of the engine to move the weight of the vehicle, but surely the weight of the vehicle is irrelevant on a dyno?

That's my stab in the dark.

Changing the diff gearing will only change the torque line you will get from the dyno, in reality there is no actual change in the power going to the wheels just the way it is delivered.

Dynos work by measuring the torque given by the wheels spinning a known mass at a speed which can be measured. From this force and speed (angular velocity) you can get the power which is being produced at the wheels.

Once you have the power you can work backwards to find your torque value.

Calculus time ,

calculating torque from power is done with the formula,

P= τ X α

Where,
P = power (kW)
τ = Torque
α = Angular velocity (rad/s) (just another way of describing the rotational speed)

So you could take this equation and say,

τ= P/α

This then would say that as the engines power is constant the torque would increase as you lowered the gear ratio.

Hope that helps a bit, It is all a bit of a dark science.

Cheers
Craig