BMW AG: 3.0L DOHC I-6 Turbodiesel
By Ward's Staff Ward's AutoWorld, Jan 1, 2009 12:00 PM

To Say BMW AG's New 3.0L Inline-6-cyl. turbodiesel checks all the boxes for greatness would be putting it lightly.

Introduced in the '09 335d sedan, as well as the X5 xDrive 35d cross/utility vehicle, no other engine captivated our seasoned panel of 10 Best Engines judges the way BMW's clean-burning diesel did.

From its ability to lay down a gutsy 425 lb.-ft. (576 Nm) of torque at 1,750 rpm — the bulk of which is available from just 1,500 revs — to the gratification of 30-mpg (7.8-L/100-km) figures accompanying such thrust, BMW has produced a spectacular Teutonic torquemeister.

But its most-pleasing attributes come from its lightweight, all-aluminum construction and advanced compound-turbocharger arrangement, both of which hardly take away from the 3-Series' stellar driving dynamics.

Saddled with only a minimal weight penalty vs. the gasoline-fueled, twin-turbocharged I-6, the 335d can bob and weave with the best. And with its pair of turbos huffing and puffing in sequence, lag-free surges of acceleration are summoned with the greatest of ease.

In the diesel world, the BMW's 88 hp/L was almost unthinkable not long ago. Yet, lessons learned from this engine's development have allowed the auto maker's new 2.0L 4-cyl. turbodiesel in Europe to produce an astounding 102 hp/L.

The magic stems from the 2-stage compressor setup: A small turbocharger spools up quickly for solid, low-end response, with a larger unit joining in at higher speeds to keep the juice flowing.

Despite a slight diesel grumble at startup and idle, the clatter quickly subsides at speed, where the 335d actually is quieter than its gasoline counterpart.

Other technical highlights include the fitment of an AdBlue urea-injection system in the exhaust, which slightly reduces horsepower compared with the 278-hp European model, yet allows sales of the 335d to extend to all 50 U.S. states.

Combined with an oxidation catalyst and soot-trapping particulate filter, this diesel's exhaust is cleaner than the surrounding air in many cities.

While our 335d tester definitely is more sport-oriented than the X5, CUV applications benefit the most from the diesel's low-end grunt and speak to the flexibility BMW built into the engine's design.

There is a premium vs. 6-cyl. gasoline models, but this powerplant becomes more attractive when factoring in the available federal income-tax credit of $900 for the 3-Series ($1,550 for X5).

As Ward's has said previously, this engine epitomizes the advancements in clean-diesel engineering and holds the best shot at erasing from the minds of American consumers the taboos associated with compression-ignition engines.

Engine type: 3.0L twin-turbocharged DOHC I-6 diesel

Displacement (cc): 2,993

Block/head material: aluminum/aluminum

Bore × stroke (mm): 90 × 84

Horsepower (SAE net): 265 @ 4,200 rpm

Torque: 425 lb.-ft. (576 Nm) @ 1,750-2,250 rpm

Specific output: 88 hp/L

Compression ratio: 16.5:1

Assembly Site: Steyr, Austria

Application tested: 335d sedan

EPA city/highway (mpg): 23/36