Special Coverage

New York Int’l Auto Show

NEW YORK – Three Mercedes-Benz cross/utility vehicles will get the German auto maker’s first 50-state diesel mill that uses urea-injection technology to purge oxides of nitrogen from diesel exhaust.

The R320, ML320 and GL320 all will offer a 3.0L V-6 diesel that generates 210 hp at 3,400 rpm. In addition, the three will be equipped with an auxiliary tank of AdBlue liquid urea solution to treat exhaust emissions.

Mercedes says AdBlue is injected into the exhaust gas stream, where the solution first breaks down into water and urea when exposed to the hot exhaust gases.

At about 330° F (170° C), the urea is broken down into ammonia that is stored in a catalytic converter. Some 80% of the ammonia is converted into harmless nitrogen and water by the downstream selective catalytic reduction converter (SCR), with overall NOx emissions reduced as much as 80%.

Mercedes says the SCR always contains some ammonia, but never too much, because it is monitored by a NOx sensor.

AdBlue is stored in a separate tank and metered into the exhaust stream with a pump. Refilling the urea solution only needs to be done at regular service intervals of about 10,000 miles (16,093 km).

But if the vehicles are subjected to very hard service, such as towing heavy loads, onboard electronics will warn the driver when the AdBlue solution level is too low.

The Mercedes CUVs will better all diesel emission standards worldwide, the auto maker claims. The three vehicles, which go on sale in the fall, will meet Tier 2 Bin 5 emissions limits and have the potential to fulfill the Euro 6 standard that’s pending.

The three CUVs, which will show off their new diesels at the New York auto show this week, only are available with a 7-speed automatic transmission.

Mercedes says the GL320’s fuel economy is 25 mpg (9.4 L/100 km), about 20%-40% better than the equivalent gasoline model, making it the most economical fullsize utility vehicle in the U.S.

To help the Bluetec diesels work with AdBlue, the engine’s piston crowns were modified to allow an improved mixture formation. Compression ratio was cut from 17.7:1 to 16.5:1, and the turbocharger with variable turbine geometry and electronic-control unit were improved and reconfigured.

The engine has third-generation common-rail injection with piezo-electric injectors. An oxidizing catalytic converter and particulate filter work to reduce diesel emissions, and particulate emissions are barely measurable, the auto maker says.

In addition to getting the AdBlue diesel option, the M-Class receives a considerable facelift, with a redesign for the front fascia and rear end. The front bumper and headlamps and a bigger radiator also are new. A 4-spoke steering wheel will be available in the GL and R-Class models.

Mercedes’ NECK-PRO head restraints are added as standard equipment, and the telematics system is upgraded with an optional Linguatronic voice control that allows whole-word input.

A hands-free Bluetooth system and a connection for iPods are available. HD Radio and Sirius Satellite Radio are optional, as is a Harmon Kardon Logic 7 surround system.