Originally Posted by HybridSS
Depends on wether its a dynojet or something like a mustang dyno. Mustang dynos and Land & Sea dynoes have some type of load cell that does DIRECTLY MEASURE TQ. Then it uses the rpm pickup to calculate the HP figure.
Dynojet claims on thier website that they are measuring HP. But this isnt really true. All they have done is calculated a standard back at the factory based on the weight and diameter of thier drum. They probably have some type of system that applies a known TQ to each drum to accelerate it and then they can calculate the software calibration for that system.
Al,
Actually Dynojet is correct.
All they are is measuring horsepower.
Horsepower as a unit of how much work was done. They know how much it weighs, they know how long it took to spin it up to the speed that they know, and from there they can calculate the amount of work (horsepower) done, and where it was done.
This is why you need an RPM reading on an engine to get a correct torque reading.
how the actual force being applied to the roller is torque, but the roller is not measuring the instantaneous rate of change and the torque being applied to it. It only has to measure the amount of time it takes to spin the known mass up, and with that it calculates horsepower.