15 April 2009

Mercedes-Benz unveiled a concept E 250 BlueTec vehicle featuring the new Mercedes 4 cylinder diesel engine and urea-SCR (selective catalytic reduction) system to meet EPA Tier 2 Bin 5 emission standards. The car, designed specifically for the North American market, was showcased at the New York Auto Show last week.

By combining the downsized engine with the 7G-TRONIC seven-speed automatic transmission, the E 250 BlueTEC achieves fuel economy of 28 mpg (8.4 l/100 km) in city traffic and 39 mpg (6.0 l/100 km) on the highway.

The 2.2 liter 4 cylinder engine delivers 150 kW (204 hp) of power and 500 Nm of torque at 1600-1800 rpm. The power unit hardware incorporates features from the series production engines, such as four-valve technology, fourth-generation common-rail piezo direct injection, 2-stage turbocharger and exhaust gas recirculation.

The exhaust aftertreatment system incorporates an oxidation catalytic converter mounted close to the engine, as well as a diesel particulate filter, which is located at the rear bulkhead in order to shorten its regeneration time.

The BlueTEC system utilizes two SCR catalytic converters with a urea (AdBlue) injector positioned upstream. The monitoring and diagnosis of the exhaust gas treatment process is handled by several sensors, including a differential pressure sensor, a Lambda probe, and NOx and temperature sensors.

For on-board storage of the AdBlue solution, the E 250 BlueTEC has a 25 liter tank equipped with a membrane pump, valve, pressure and temperature sensors and an electrical heating unit, which prevents the urea solution from freezing at low temperatures. The tank volume is sufficient for the duration of a full service interval and is refilled as part of the regular maintenance schedule. The AdBlue tank is integrated into the spare wheel well in the trunk.

The E 320 BlueTec launched in 2006 and currently available in the US and Canada utilizes an adsorber catalyst for NOx control, and was certified to Tier 2 Bin 8 emission standards. Thus, the vehicle could not be sold in states that require California emission standards (Bin 5 or cleaner). In 2008, Mercedes launched several SUV models equipped with urea SCR technology, certified to Tier 2 Bin 5 standards.

Source: Daimler