Torque question

[Sinister Angel]

If torque to the wheels is dependant changes as you go through the gears, how do you get one torque rating at the wheels when you put the car/truck/bike/scarab that you jigga rigged to work on a car dyno/whatever on the dyno?

 

[KaosFire]

Most cars have a 1:1 gear so the torque doesn't multiply through the drivetrain (theoretically). If a car doesn't have a 1:1 like some fwd cars, you'd have to correct for that through the dyno computer.

 

[Sinister Angel]

Ahh, I gotcha, so basicly they just have you run the dyno in 4th (which is where I'm assuming most cars have the 1:1 gear)?

 

[KaosFire]

yup
thats where mine is.

really, you can run the dyno in any gear but there are many factors one has to consider. Like how much friction that gear ratio provides, how fast you go through the RPM's in that gear, how much vibration the car gives in low RPMs (if you start in say...6th gear. Can you dyno from 1000?) and if the dyno can handle the torque you provide to it (really high for low gears).

I've had discussions about this with others and I can't seem to find any consensus on this other than dynoing in 4th is because of the 1:1.