Mercedes-Benz has long been making efficient exhaust treatment systems. This is the reason why when talking future diesel engine technology, BlueTEC will always enter the conversation. The engines of BlueTEC vehicles can be considered as one of the world’s cleanest as they are able to meet even the strictest of standards in global emissions.
The E 250 BlueTEC is Mercedes-Benz’s way of showing that it is possible to combine a four-cylinder engine that has optimized fuel consumption with the BlueTEC technology found in this E-Class.
This E 250 BlueTEC was exclusively manufactured for the North American market. When the engine is paired with the seven-speed 7G-TRONIC automatic transmission, the E 250 results in a fuel economy rating based on U.S. FE standards of 28 mpg for city traffic and a rating of 39 mpg for the highway.
It is able to meet the most rigid of emissions standard like the Bin 5 in the U.S. The E 250 can also fulfil the guidelines set by the EU6 legislation though this is not expected to be implemented by September 1, 2014. It was important that the E 250 be able to satisfy the legal requirements when it came to on-board diagnostics.
One of these was to lower the internal raw emissions being produced by the engine and therefore the new four-cylinder 2.2-liter CDI engine had to be redeveloped. The electronic engine control system is so sensitive that it can react immediately to a wide range of operating conditions in order to optimize the engine’s combustion process.
This time the power unit hardware integrates a number of features that are part of the series production engines like the 2-stage turbocharger, fourth-generation piezo common-rail direct injection, exhaust gas recirculation, and the four-valve technology.
The exhaust gas treatment system in particular contains just an oxidation catalytic converter that has been fixed near the engine. It also comes with a diesel particulate filter placed in the rear bulkhead leading to a reduction in its regeneration time.
There are two SCR catalytic converters at the center of the BlueTEC. The SCR stands for Selective Catalytic Reduction and these converters also have what is known as an "AdBlue" injector located upstream. This injector is made of an aqueous urea solution that while synthetic, can convert nitrogen oxide to a harmless nitrogen gas inside the converters.
In order to monitor and diagnose this rather hig-tech gas treatment process, the E 250 makes use of a number of sensors like temperature sensors, differential pressure sensor, and Lambda probe plus NOx. To be able to store this "AdBlue" solution, the E 250 contains a 25-liter tank that has both temperature and pressure sensors, membrane pump and valve.
There is even an electrical heating unit that ensures the "AdBlue" 33% urea solution does not freeze even when the vehicle experiences very low temperatures. In addition, the 25-liter tank is enough to make sure that the full service and the refill can be maintained on a regular basis.
The tank has been placed on the spare wheel well in its boot. As such, with the 4-cylinder engine combined with its SCR technology, the E 250 does not only offer excellent fuel economy and lower emissions, it also delivers extraordinary performance and a fun factor.
As what can be expected from any Mercedes-Benz vehicle, the powertrain offers smooth characteristics owing to two Lanchester balancing shafts. The BlueTEC technology is expected to be part of the series production model to be released in Europe by the autumn of 2009 through the E 350 BlueTEC.
The E 350 however uses a V6 diesel engine that delivers 155kW or 211 hp of power and maximum torque of 540 Nm. With this, Mercedes-Benz customers should expect a series production vehicle that conforms with EU6 emission standards even if it has yet to be implemented in September 2014.