Quote:
Originally Posted by 1speedbike
People have consistently seen 270-280 HP range from the 135i on a dynojet, more like 260-270 on a mustang dyno. Though I have seen some naturally "good" cars on naturally "good" dynos get up to 285, even 290.
That said, looks like there's either a ~10-12% drivetrain power loss (closer to 12% on HP, 10% with torque)... Either this is a "good" car and a "good" dyno... OR... I know N/A RWD engines usually experience a 15-20% power loss versus the about 12-15% the turbo engine loses from crank to wheels. This would mean that the 128i is slightly underrated from the factory and would be making more like 240-245 HP and 215-220 ft lbs at the crank. Either way, that's great, because either you have pretty low drivetrain power loss, or you have a little more power than you thought. Cool!  |
power loss is dictated by the drivetrain, not by the induction on the motor. the reason we have these general numbers for either the n/a or turbo... is we take it BMW has rated the motor at the flywheel and given us a 'true' number, then when we dyno the rear wheel power. from here our calculations would often say that either the drivetrain in the turbo is more efficient (which it's not) so actually its simply the flywheel hp dictated by bmw is more accurate on one than the other.
what he's shown for his car based on bmw claimed 230hp his loss is about 14% giving him 198hp at the wheels. That 14% may be true or his car on a flywheel dyno may actually make 220 or even 250 hp, we don't truly know the 'losses' and are doing nothing more than guessing.
either way he's got a nice running car with multiple 'backed up' runs so that's a great baseline to know where he's at and for future measurement of mods if he makes any.
Also it's another great feather in the cap of a great running BMW that is often belittled here on this site for no good reason. 200 rwhp is pretty damn good in a 3000lb car...