DaimlerChrysler AG 3L DOHC V-6 Turbodiesel
By Bill Visnic WardsAuto.com, Dec 20, 2006 9:07 AM

Two identical cars. One has a gasoline 3.5L V-6, the other, a 3.0L V-6 diesel.

The gasoline car runs from 0-60 mph (97 km/h) in 6.5 seconds. The diesel car takes a tenth of a second longer to get there but makes up for it with 35% better fuel economy.

With $3.50-per-gallon gasoline anything but a distant memory, you’d take that diesel, wouldn’t you?

We sure would.

“A game changer” is the summation of one 10 Best Engines judge of the DaimlerChrysler AG 3L DOHC V-6 turbodiesel, an all-new, 72-degree vee architecture developed by DC’s Mercedes-Benz unit to replace its inline 6-cyl. turbodiesel.

If it were just a fuel-economy play, it would be mighty convincing, achieving 27 mpg (8.7 L/100 km) city and 37 mpg (6.4 L/100 km) highway.

But the buyer of this new diesel gets noise vibration and harshness quality levels comparable to gasoline engines. Goodbye to that nagging perception issue. Just as important, the new V-6 wields a hefty performance hammer.

DaimlerChrysler 3L DOHC V-6 turbodiesel performs on par with similar-sized gasoline engines.

At 208 hp and a thumping 400 lb.-ft. (542 Nm) of torque in the ’07 Mercedes E320 Bluetec application, the new-generation V-6 turbodiesel is stronger than the 3.2L inline unit it supplants.

And it has more torque than the auto maker’s 5.7L Hemi V-8. Need we say more? Four hundred pound-feet makes something happen.

Incidentally, the same engine, with slightly different specs, is in the ’07 Jeep Grand Cherokee CRD, which we also tested – and found to be slightly less refined.

Mercedes engineers ladled on every available technology to assure its new all-aluminum V-6 turbodiesel lives up to the fuel-economy promise while attaining new levels of NVH and cleanliness.

The high-pressure common-rail fueling isn’t news in the diesel business, but the 22,700-psi (1,600-bar) system pressurizes the latest piezohydraulic fuel injectors that just plain eradicate diesel clatter.

Cold starts still are a tad noisy, but once the engine is warmed up, the “dieselness” is indistinguishable from the mechanical gnashing of a gasoline engine’s ancillaries – even at idle.

There’s a clatter-quieting pilot injection and as many as five total injection events possible for each and every combustion event. The twin balance shafts also boost NVH.

And there’s the latest in variable-nozzle turbochargers to minimize turbo lag, although there’s still a moment of dead-throttle anxiety just off idle and before this powerhouse can start delivering its peak torque at just 1,600 rpm.

Now, about those emissions. Unless you’ve spent the last couple years in a Tibetan retreat, you know diesels have trouble complying with the latest U.S. emissions standards for oxides of nitrogen (NOx) and particulate matter.

This year, the E320 Bluetec uses the first phase of the Bluetec exhaust-aftertreatment system that will, by sometime next year, cleanse NOx and particulates to the point where diesels so equipped can be sold nationwide.

That will require a suite of aftertreatment components highlighted by a urea-injection system to reduce NOx to acceptable levels.

For now, the E320 Bluetec uses an oxidizing catalyst, an NOx-scrubbing catalyst, a particulate filter and a basic selective catalytic reduction (SCR) converter to take one final swipe at NOx. Mercedes says this system makes the diesel compliant with federal Tier II, bin 8, emissions standards.

To get to the diesel Valhalla of Tier II, bin 5 – low enough to make diesels salable even in California – the urea-injection system will be required.

Don’t worry – they’ll work out the emissions thing. DaimlerChrysler’s new-generation 3L V-6 turbodiesel is the real deal, right now. Spectacular performance and serious fuel economy now officially co-exist.

bvisnic@wardsauto.com