The New 2013MY Mercedes-Benz GLK250 BlueTEC 4MATIC Sport Utility Hits the Road

U.S. journalists are test-driving the very first 2013MY Mercedes-Benz GLK250 BlueTEC 4MATIC sport utility vehicles, arriving in the U.S. by the end of April. The new GLK model represents the first diesel-powered entry in the mid-size SUV market. With segment-leading fuel economy of 24 city/33 highway, the GLK250 BlueTEC 4MATIC is available for retail sale by April 30, with pricing that begins at $38,590 (excluding $905 destination charge).
High-Tech Four Cylinder with Balance Shafts
The 2013MY GLK250 BlueTEC 4MATIC boasts the most powerful four-cylinder diesel engine in the SUV world. Its 2,143 cc direct-injection engine is rated at an even 200 horsepower and 369 lb-ft of torque. The all-aluminum, in-line four-cylinder engine makes use of four valves per cylinder and dual overhead camshafts with vane-type variable valve timing. To smooth out the inherent vibration of an in-line four-cylinder engine, two Lanchester balance shafts spin at twice the crankshaft speed.
BlueTEC Refinements
Fuel pressure for the BlueTEC direct fuel injection system is approximately 29,000 psi (or 2,000 bar) that makes possible even more power and lower exhaust emissions. Higher ignition fuel pressure means the four piezo injectors can be adjusted even more precisely as engine load and speed change. This system places the four-cylinder diesel at the head of the field when it comes to diesel engines for passenger vehicles.
AdBlue Injection
To ensure the GLK250 BlueTEC 4MATIC meets exhaust emission regulations in all 50 states, the BlueTEC system uses AdBlue injection to make the diesel as clean as a state-of-the-art gasoline engine. A water-based urea solution, AdBlue is carried in its own small tank and metered into the exhaust in minute quantities, so the tank only needs to be refilled during routine scheduled maintenance. When AdBlue is injected into pre-cleaned exhaust gas, ammonia (NH3) is released, converting nitrogen oxides into harmless nitrogen (and water) in a downstream catalytic converter. Called SCR, for selective catalytic reduction, this process creates the most effective method of exhaust gas after-treatment currently available.
Two-Stage Turbo System
To ensure responsive power over a broad speed range, the new engine features an innovative two-stage turbocharger system that's comprised of a small high-pressure (HP) turbocharger and a large low-pressure (LP) turbocharger. Unlike a traditional biturbo system, the two turbochargers are connected in series, with the HP unit located directly at the exhaust manifold and the LP unit downstream.
Exhaust gas flow spins the HP turbine at up to 215,000 revolutions per minute, and the turbine housing has a bypass duct that can be opened or closed by a vacuum-operated wastegate. When the bypass is closed, all the exhaust flows through the HP turbine, allowing high boost pressure to be developed, even at low engine speeds. As engine speed increases, the wastegate opens, and exhaust gas begins to bypass the HP turbine and flow directly to the second LP turbine.
Exhaust gas from the HP turbine and its wastegate reconverge downstream to drive the LP turbine at up to 185,000 revolutions per minute. At intermediate engine speeds, the wastegate is opened wide enough so that the HP turbine ceases to perform any appreciable work. This allows full exhaust gas energy to flow through the downstream LP turbine, which then does all the work.

Courtesy of: Mercedes-Benz Blogspot