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Old 06-19-2011, 07:23 PM
80 SS El Camino
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Engine dyno to chassis dyno numbers

I have a 385 stroker Chevy I put together and actually watched the dyno the day it was born. It pulled a few 450's and topped out at 460 hp. Great, two years later and only 1200 miles on it I had the opportunity to chassis dyno it. I was a little disappointed at a 337 hp at the rear wheels. That's a 123 hp drop from the flexplate to the rear wheels, or 23% drop.
I have a built TH 350 that's pretty stout and the torque converter is pretty solid too.
Anyone else experience numbers like this?


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Old 06-19-2011, 07:39 PM
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I've never measured the difference of drive train losses on mine, and it seems like a lot, but parasitic loss can be big compared to the bare motor on a stand. Add accessories, the turbo trans, differential drag, on and on, I suspect you aren't alone. Also keep in mind the motor dyno test is conducted under ideal conditions, temperature controlled, etc.
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Old 06-19-2011, 07:41 PM
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~20% is about normal for drivetrain loss in a street car. Also, when you had the engine dyno done the first time, were there accessories on the engine, power steering pump, alternater/generater, fan, etc? A race only car might only loose 10% in the drive train, but they rarely get on a chassis dyno.
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Old 06-19-2011, 07:56 PM
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The motor was set up on the stand the way it sits in the car now. March serpentine kit with 1 wire alternator, aluminum water pump and ps. Nothing else. I run an electric fan now as well. I guess if +-20% is normal then I won't beat myself up on what could be wrong.

What I might try next is a tried and tested TCI torque converter and stepping up to 1 3/4 headers instead of the 1 5/8 I have now. (running 3" exhaust)

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