The 2007 BMW 335i will be in showrooms next month, and is the first application of BMW's new twin-turbocharged 3.0-liter inline-six. This is a big deal because BMW has had only two short affairs with turbocharged gasoline production cars--the 2002 Turbo in the mid-70s, and the E23 745i in the early 80s--and neither was sold in the U.S. As the saying goes, third time's the charm.
BMW fit this new engine with two small-displacement turbochargers--instead of one larger unit--in an effort to reduce lag. And for the most part, it worked. Behind the wheel, you're vaguely aware that this engine doesn't have quite as crisp a throttle response as its normally-aspirated siblings do. But you don't care--you're too busy trying to hold on for dear life.
This is one hell of a motor, pulling smoothly and strongly from idle all the way to its 7000-rpm fuel cutoff. There's no boost gauge, and since you barely hear the turbos spooling, it's easy to forget they're even there. Once you've adjusted to the slight lag in power delivery following big, sudden throttle openings, all you notice is the sound of that silky in-line six.
BMW says that this engine makes 300 horsepower and 300 lb-ft of torque. We were so impressed with its power that we couldn't help wonder if that was a conservative rating. Wasting no time, I swiped the keys and drove to a local dyno shop to find out.
We used a DynoJet chassis dyno, which measures an engine's power output at a vehicle's rear wheels. Because of frictional driveline losses, this number is always lower--generally by fifteen to twenty percent--than the quoted power output from the manufacturer, which is measured at the engine itself.
Here's what we found:
The non-turbocharged 330i, rated by BMW at 255 hp and 220 lb-ft of torque, puts about 200 hp and 180 lb-ft to the rear wheels. That's roughly a twenty-percent loss. Since they have similar drivelines, you'd expect the 335i to put down 235 hp and 250 lb-ft.
But it didn't. It put down a whole lot more: 275 hp and 300 lb-ft. A few quick taps on our trusty calculator shows that this engine is likely putting out closer to 350 hp and 360 lb-ft of torque.
Technical editor Don Sherman's ears perked up at all this number crunching. With all that power, he wondered, is the 335i faster than the outgoing 333-hp E46 M3? We waved goodbye to the shiny new coupe's rear tires, and sent him to find out.
Don coaxed the 335i to 60 mph in 5.1 seconds--only 0.3 seconds slower than the M3. The 335i covered the quarter-mile in 13.6 seconds @ 104 mph--again, only 0.2 seconds and 1 mph behind the M3.
So in an all-out drag race, the 335i comes close, but can't quite match the M3's blistering acceleration. Those numbers, though, only tell half the story. Have a look at the top-gear acceleration figures. In sixth gear, the M3 needs 14.7 seconds to get from 30 to 70 mph - but the 335i does it in only 12.5.
That, my friends, is the beauty of this engine. At full bore, it's as fast as an M3. But at moderate engine speeds, it's even faster. What a great way to keep us all interested until the next M3 comes along.
Click below for exclusive video coverage of the test.