Can you do a “coastdown” test on our chassis dyno to measure the dyno and vehicle losses, and then correct the chassis torque and HP to get flywheel torque and HP?
Doing a coastdown test of the vehicle you just tested to estimate the losses in the driveline, to then come up with flywheel HP is VERY MISLEADING. Reason is because the losses with power ON are much higher than when coasting, especially for an automatic trans. For example, if the losses from coastdown at 4000 RPM show 32 HP, the losses with full power will be much higher (perhaps 100 HP for a 500 HP engine) when accelerating. Tire slippage alone will be 3-10%, which equates to a direct loss of that percentage in power. (During coastdown, tire slippage is 0%.) The difference between full power and coasting gear box losses are the difference between power-On efficiency and simple “spin losses”. Torque converter slip during power-On can be 30% or more, again a huge loss that is 0 when doing a coastdown.
