By Jim Kerr; photos by Bob McHugh

Photo Gallery:
2009 Mercedes-Benz BlueTec diesel models

Diesel powered vehicles have always been popular in Europe. High fuel prices there have been offset by the 30% better efficiency of the diesel engine. In Canada, the variety and availability of diesel powered cars has been limited by pure economics: we just don’t buy enough diesel-powered cars in Canada to justify designing one for North American standards and supporting it with dealer training and parts supplies. It’s a sad fact, but unless U.S. motorists buy more diesel-powered cars, we will see a limited number of diesel models in Canada.

Mercedes-Benz thinks that is about to change. Several factors have come into play. High fuel prices in the U.S. and Canada are making drivers think about alternatives; low-sulphur diesel fuel is now sold throughout Canada and the U.S.; and finally, tough new emissions regulations on diesel-powered vehicles are now being met with the Mercedes-Benz BlueTec technology.

Mercedes-Benz first introduced BlueTec to Canada in their E320 sedan. This car uses an oxidizing converter and a particulate trap in the exhaust system to reduce the tailpipe emissions. The power and smoothness of this vehicle has enticed many drivers. The E320 accounts for 13% of all E-class sedan sales in the U.S. California has implemented tough new regulations that require further reductions in emissions, and Mercedez-Benz is ready.

Mercedes-Benz M-Class, R-Class and GL-Class CDI models
Bluetech AdBlue fill point
Mercedes-Benz M-Class, R-Class and GL-Class CDI models (top photo); Bluetech AdBlue fill point. Click image to enlarge

This fall, three new Mercedes models will be in the showrooms. The ML 320, the R 320 and the GL 320 are all now powered with a 3.0-litre V6 diesel engine with BlueTec technology and AdBlue injection. The incorporation of AdBlue injection to the BlueTec emissions system enables these vehicles to be the first to meet the tough California emission standards, the toughest in North America. These emissions standards are applied in seven other States this year and will be joined by six more by 2012. Canadian drivers may fall under these tough standards too, as both B.C. and Quebec are looking at possibly implementing the regulations.

So what it this BlueTec and AdBlue technology? BlueTec reduces NOx emissions in a catalytic converter that breaks the gas down into Nitrogen and Oxygen. It also incorporates a particulate filter that allows exhaust gases through freely but traps small particles that we see as soot or smoke. With BlueTec, the diesel exhaust looks as clean as a gasoline-powered vehicle but AdBlue makes it even cleaner.

AdBlue is an aqueous urea solution, which when injected into the exhaust stream causes ammonia (NH3) to be released. The ammonia reacts with up to 80% of the remaining NOx to break it down. The results are pure nitrogen, which makes up about 76% of the normal atmosphere, and water vapour.

Each vehicle will have a separate tank to store the AdBlue solution. This solution is pumped into the exhaust as a vapour at a controlled rate by the engine computer. Different driving conditions will require different amounts of AdBlue injection (high cylinder temperatures produced by heavy loads produce more NOx) and this is monitored by a NOx sensor. There is enough solution on board to last about two maintenance intervals, so filling the AdBlue tank at every oil change will become part of routine maintenance.

The engine will operate fine without AdBlue, but because the emissions standards are not met without the injection of AdBlue, Mercedes-Benz had to work with regulators for a solution to keeping the vehicles within standards. If the tank (28 litres on the ML320 BlueTEC) is getting low, a warning message will tell driver several hundred kilometres in advance that the tank needs to be filled. This is followed by other warnings. If the driver ignores the warnings and drives with an empty AdBlue tank, then the vehicle will only start 20 times. Each time the driver starts the vehicle, a message will display the remaining number of starts before the vehicle must be towed. With the capacity of the AdBlue system and the multiple warnings, there is never a need for a driver to run out of AdBlue. Mercedes-Benz has offered the technology to other manufacturers and says the AdBlue solution will be readily available not only at dealers but at other retail outlets as well. Currently the price is near a dollar a litre for the AdBlue solution.

Diesel fuel is now priced higher than gasoline, but this is related to production capacity, not refining cost. Even with the higher fuel price, the increased efficiency of the diesel engine combined with excellent torque enable smaller more fuel efficient engines to used. Is there a clean diesel in your future? Mercedes thinks so.

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