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      03-09-2006, 09:22 AM   #11
sdorn's Avatar

Drives: 2006 Jet Black 325i
Join Date: Feb 2006
Location: Atlanta

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Originally Posted by carlitosz
200whp - 205whp.
I don't think those are crazy numbers. These cars are supposed to be much more efficient than other cars, so I could see using a 10% or 12% estimate for drivetrain loss. Generally (at least from what I have read) you use between 15% - 20% for drivetrain loss depending on the car and the transmission. I would also assume that BMW slightly underrates the horsepower on their cars as many other manufacturers do.

If the 325i was actually putting out closer to 225 hp at the crank, then at a 12% loss you would be pretty close to 200rwhp. Using the same logic, I wouldn't be surprised to see 330i's putting down around 235 - 240rwhp.

It is also common for a car manufacturer to exaggerate the difference between two different models to make it seem like they are further apart than they are. For example, back in 2000 and 2001 when Chevrolet was selling the Camaro and Firebird, they would often dyno at over 300rwhp completely stock. They were only rated at between 300 and 320hp at the crank by Chevy. The reason was that Chevy didn't want it to be so obvious that the Corvette and Camaro had virtually the exact same horsepower.
2008 Sparkling Graphite 535i
2009 Land Rover LR2
2003 Porsche 911 Turbo (SOLD)
2006 Jet Black 325i (SOLD)
2001 Bullitt Mustang (450rwhp - SOLD)