2009 BMW M3 Sedan: Making Sweet Dyno Music
June 14, 2009
This week's Car of the Week, our long-term 2009 BMW M3, starts things off with a hair-raising shred of sleepy Westminster, California's early-summer atmosphere.
That's where we subjected unsuspecting neighbors to repeared shrieks of the M3's 4.0-liter V8 as we caned it across its rev range range to the 8400-rpm redline at full throttle.
MD Automotive once again rented us time on their Dynojet chassis dyno for this exercise, which we undertook purely in the name of science. We swear.
BMW says the M3 generates 414 horsepower at 8300 rpm and 295 lb-ft of torque at 3900 rpm. Turns out they were right about the output.
Make like Kriss Kross for the dyno chart and video.
Unlike in the M5, where the "power" button unleashes an additional 100 hp, pressing the M3's "power" button only sharpens the throttle response. The M3's owner's manual doesn't make any claims of additional power, but we checked it on the dyno anyway. Sure enough, we found the same power irrespective of the button's state.
In total, we performed four runs and they were all virtually identical. Run-to-run variation just isn't part of the M3's playbook. Normal aspiration has its advantages.
Click the dyno chart for a larger image:
We apply weather correction for normally aspirated and supercharged cars. The SAE correction factor for this run is 1.05 since we tested the M3 on a relatively warm day.
This is an especially flat torque curve for a non-turbocharged engine. At 6700 rpm, the little V8 gets a second wind, too, and output swells upward once more before its very gentle taper as it approaches 8300 rpm..
Factoring in drivetrain loss, the 376 horsepower we measured at the M3's wheels is about what we'd expect from a 414-hp flywheel claim. Keep in mind that our result was achieved running California's crummy premium fuel, which is only 91 octane. Pretty impressive for a high specific-output engine like this one.
The lack of any significant sag in the power delivery between 3800 and 7800 rpm explains the engine's uncanny rev-forever character that you feel when you wind it out. It also demonstrates the significance of high revs when peak torque--we measured 274 lb-ft at the wheels in this case--is relatively modest in V8 terms.
Another observation is that although the M3 V8's maximum engine speed is indeed 8400 rpm, it really isn't the practical rev limit. Power clearly falls off so hard after 8300 rpm that the additional 100 rpm is useless. Come to think of it, early press releases listed this engine's redline at 8300 rpm. This ambiguity is likely a matter of engineering versus marketing.
Nevertheless, this V8 is one hell of an engine. What more is there to say?
Jason Kavanagh, Engineering Editor