BMW's 3.0L N55 Turbocharged DOHC I-6: Ridiculously Efficient

The temptation may have been great for BMW AG to rest on its laurels and feel confident its inline 6-cyl. engines had secured their place in the pantheon of powertrain excellence over the past 40 years.

After all, the Bavarians have amassed more Ward's 10 Best Engines honors than any auto maker on the planet — 25, and counting, since the competition began in 1995. And 20 of the awards were for I-6 gasoline engines.

Distill the data further, and nine of those honored 6-cyl. engines displaced 3.0L, give or take a cubic centimeter.

The latest honoree is — you guessed it — a 3.0L I-6 that produces 300 hp and 300 lb.-ft. (407 Nm) of torque with ridiculous ease and efficiency. Its place on this year's list was locked as soon as the first Ward's editor stepped on the accelerator during our test drive of the '11 335i sedan.

This turbocharged, direct-injection N55 engine carries over BMW's outstanding I-6 all-aluminum architecture from the N54, which earned 10 Best Engines honors in 2007, 2008 and 2009 with twin turbochargers producing the identical 300 hp and 300 lb.-ft. of torque.

The key difference with the N55 is that it uses a single twin-scroll turbocharger that minimizes turbo lag.

The new turbocharger builds pressure faster because the housing design provides a more direct route for exhaust gases.

DISPLACEMENT (CC): 2,979

BLOCK/HEAD MATERIAL: ALUMINUM/ALUMINUM

BORE × STROKE (MM): 84 × 89.6

HORSEPOWER (SAE NET): 300 @ 5,800 RPM

TORQUE: 300 LB.-FT. (407 NM) @ 1,200 - 5,000 RPM

SPECIFIC OUTPUT: 100 HP/L

COMPRESSION RATIO: 10.2:1

ASSEMBLY SITE: STEYR, AUSTRIA

APPLICATION TESTED: '11 BMW 335I SEDAN

EPA CITY/HIGHWAY (MPG): 19/28