Does testing in different gears result in different horsepower?
Many factors contribute to reasons why the reported horsepower (hp) is different when testing in different gears, but none have anything to do with the calculations present in the dyno. These factors include: • Vehicle inertia is assumed in the dyno software. The value is fixed. If it is not a perfect match to the vehicle, then changing the rate of acceleration changes the dyno results. • Altering the rate of acceleration changes parasitic losses in the vehicle drivetrain due to stress loads changing on gear faces. • Altering the rate of acceleration changes the inertia of the air/fuel charge in the vehicle intake, thus changing the power output of the engine. • Altering the rate of acceleration changes the amount of power “left over” at the wheels because it uses more of the engine’s power output to accelerate itself and driveline components. Nothing is free. The best choice is to dyno at the same rate because changing the rate will surely change the outcome of your test data. Below i
