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Old 05-20-2011, 12:11 AM
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rearwheelhorsepower

i saw on the net where a car made 475 rear wheel horsepower just wondering what the hp/tq of the motor would have to be to make that much to the rear tires

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Old 05-20-2011, 12:53 AM
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It all depends on the parasitic losses generated by the vehs. drive train. An automatic trans would cause a little more of a loss than a standard trans. Also synthetic lubricants instead if dino oil in the trans...rear end. If he's pushing 475 at the wheels with the good lube through a standard trans then I would guess he see's 520-525 hp at the flywheel....just a guess.
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Old 05-20-2011, 02:24 AM
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Quote:
Originally Posted by crowerjunky
i saw on the net where a car made 475 rear wheel horsepower just wondering what the hp/tq of the motor would have to be to make that much to the rear tires
You will often hear 12% to as much as 20% as the amount of loss through the drive train, etc. when comparing flywheel and rear wheel output. If I had to make a WAG at it, I'd say about 15% is the median for a well maintained 2wd car.
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Old 05-20-2011, 11:37 AM
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Closer is 20 + percent. In my engines the loss in a automatic trans is big. The standard lightduty 4 spd hp lost is possibly under 20 percent. It may be power level related.

A 350 open header flywheel hp was 310 off a Detriot engine brake dyno. The roller dyno could not break 200 at the wheels. That is with a TH350, a TH400 would be worse. There is less power lost in the Mopar 727TF type supposedly.
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Old 05-26-2011, 01:15 AM
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[QUOTE=spinn]Closer is 20 + percent. In my engines the loss in a automatic trans is big. The standard lightduty 4 spd hp lost is possibly under 20 percent. It may be power level related.

A 350 open header flywheel hp was 310 off a Detriot engine brake dyno. The roller dyno could not break 200 at the wheels. That is with a TH350, a TH400 would be worse. There is less power lost in the Mopar 727TF type supposedly.[/QUOTE

just out of curiousity did the car have a full exhaust when it was on the wheel dyno ?
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Old 05-26-2011, 01:44 AM
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Quote:
Originally Posted by spinn
It may be power level related.
No "may be" about it IMO. The energy used to overcome losses through the drivetrain and etc. is more or less finite, so an increase in output will mean that a smaller percentage is used to overcome the losses than an engine w/less output.

IIRC the Powerglide and C4 have the least power loss of the common AT's (possibly other trannys are better, but also weaker- to the point of being excluded for performance use) and the C6 is the highest of the AT's. TC slippage is a factor as well.
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