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, Fri, 20 Sep 2002 08:14:14
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...though I still can't confirm it, after thinking about it a bit, I figure more than likely the 12% figure is derived from running the car in a steady state (i.e. fixed RPM) condition on the chassis dyno, and comparing the number to what you get with just the engine hooked up to your water brake dyno or equivalent under a similar condition. Since the RPMs are steady state, all the spinning parts are already spun up and not drawing energy to accelerate themselves.
Everything I've read supports your statement that nowadays such engine dyno tests are done with or corrected for all the appropriate accessories (i.e. pumps, alternators) and exhaust systems in place.
So, it would appear that your initial comment about taking into consideration the inertial losses in spinning everything up during a dynamic acceleration situation is the correct one. The 12% number needs to have those inertial losses tacked on top of it in this situation.
One site noted a rough approximation technique of adding 7% additional mass to the vehicle to account for the inertial energy loss in acceleration. Unfortunately the site didn't provide any more info on where this number came from.
Surprises me a little bit that losses are so great just from viscous friction in the bearings, etc, but it's certainly not unreasonable.
So the search continues for more data on the flywheel, gears, wheels, and driveshafts. Nobody on the performance board answered re: Cd, A, weight balance, CG height...any thoughts on any of these?
'Roo
posted by 12.13.238...
, Thu, 19 Sep 2002 11:53:31, Thu, 19 Sep 2002 17:28:45, Fri, 20 Sep 2002 08:14:14, Wed, 18 Sep 2002 17:02:40
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