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      06-18-2006, 04:21 PM   #20
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Drives: E90 330i 6MT
Join Date: Nov 2005
Location: Torrance, CA

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Originally Posted by new2the3
normal loss for auto is 20%, the #s the 330i auto put down should be about 10hp more and a few more ponies for the 6mt. The numbers look low.
Numbers may seem low, but . . .

"The difference between flywheel horsepower and rear-wheel horsepower will vary from vehicle to vehicle, depending on many factors," adds Gale Banks Engineering, "but we find that rear-wheel horsepower is usually between 18 percent and 25 percent less than flywheel horsepower."

Based on this, I calculated expectations under OPTIMAL CONDITIONS for rear wheel horsepower for the 2006 E90:

FLYWHEEL HORSEPOWER: 215 hp @ 6250 rpm
Rear WHEEL (18% less): 176.3 hp calculated off factory numbers
Rear WHEEL (25% less): 161 hp calculated off factory numbers

Rear WHEEL (18% less): 209.1 hp calculated off factory numbers
Rear WHEEL (25% less): 191.25 hp calculated off factory numbers

Run conditions were less than ideal (hot day, increased humidity). Yet, regardless of this, our dyno runs were still generally on par and occasionally better than what would be expected as calculated from factory specs within statistical margin of error.

So the numbers were right on the money.
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