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Benz Bluetec drives diesel's rebirth

The time has come. With the mandated arrival of clean (relatively speaking) diesel fuel in Canada and the U.S. this fall, we will finally have an opportunity to find out for ourselves what the Europeans have known for years.

  • Choosing a car at dealership. Thoughtful grey hair man in formalwear leaning at the car and looking away

Las Vegas—The time has come.

With the mandated arrival of clean (relatively speaking) diesel fuel in Canada and the U.S. this fall, we will finally have an opportunity to find out for ourselves what the Europeans have known for years.

That is, diesels rule!

They're fuel-efficient, with lower CO2 emissions than comparable gasoline engines, and fun to drive.

Leading the way in our education will be the Mercedes-Benz E320 Bluetec sedan, the cleanest diesel in the world, according to Klaus Maier, vice-president of the Mercedes Car Group.

It is the first diesel passenger car to be sold here that surpasses the tough Tier 2, Bin 8 emission standards applicable in 2007 in Canada and 45 U.S. states.

Compliance with even tougher Tier 2, Bin 5 standards that take effect in 2010 is promised.

At that stage, the car can be sold in all 50 U.S. states.

Mercedes and Volkswagen have been selling diesels here for years, but we haven't been getting the really good stuff.

We couldn't, because the exorbitant sulphur levels in our diesel fuels — up to 500 parts per million (ppm) — would poison the sophisticated exhaust after-treatment systems that are necessary to control emissions to newly mandated levels.

European diesel fuels, by contrast, had sulphur levels below 10 ppm. Our new "clean" diesel fuels have an upper limit of 15 ppm.

That's not as low as auto makers would like, and other fuel issues remain, but it's good enough for us to start seeing some of Europe's high-tech diesels.

And what a revelation they are.

Far removed from the noisy, sooty oil burners of the 1980s, these new powerplants are smooth, strong and amazingly quiet.

Only a bit of audible knock at idle — apparent from outside but not inside the new E320 Bluetec — indicates it's a diesel.

Until you touch the accelerator pedal, that is. Then you get the message: this thing leaps ahead like a reborn muscle car.

Gobs of low-end and mid-range torque are a diesel trademark, hence their reputation as low-speed plodders, but today's diesels make good power across a broad range.

The 3.0-litre V6 CDI (common-rail direct injection) engine is the starting point for Mercedes's Bluetec strategy. It generates 208 hp and 400 lb.-ft. of torque, making it a solid all-round performer. And it can provide fuel economy of just 6.7 L/100 km.

Bluetec technology involves four elements:

  • clean fuel and optimized combustion minimizing raw emissions from the engine;

  • an oxidizing catalytic converter to treat carbon monoxide (CO) and unburned hydrocarbons (HC) in the exhaust;

  • a particulate filter that cuts exhaust-borne particulate matter to barely traceable levels;

  • nitrogen oxide (NOx) after-treatment.

    Nitrogen oxides, which are smog-forming gases, are the only exhaust emission components that are still emitted in greater quantities from diesel engines than from their gasoline counterparts, due to the nature of diesel combustion.

    That NOx after-treatment will take two forms.

    In stage one, which is applied to the Bluetec vehicles available in 2007, it consists of an NOx storage catalyst and an additional SCR (selective catalytic reduction) catalyst.

    The next stage, set for introduction in 2008, targets the tougher, 50-state requirements bowing for the 2010 model year.

    It will replace the passive NOx storage catalyst with an active treatment system.

    It injects a non-toxic aqueous urea solution into the exhaust flow, breaking down up to 80 per cent of the NOx into nitrogen and water in the downstream SCR catalyst.

    Mercedes calls that solution AdBlue — hence Bluetec.

    The Bluetec system has been successfully used for three years in Europe in heavy-duty trucks.

    A regulatory hurdle remains to be cleared before that second stage can be introduced in North America, however.

    Current U.S. emission regulations, which Canadian regulations parallel, stipulate that no specific consumer action be required to ensure the function of emissions systems throughout the life of the vehicle.

    Periodically adding AdBlue to a storage tank might be considered a required owner action.

    Mercedes, however, has sized the AdBlue tank so that it will only need refilling at routine maintenance intervals by the dealer, freeing the consumer of the task.

    Negotiations are still under way on the interpretation of that regulation.

    General Motors is counting on use of similar technology for a light-duty truck diesel it plans to introduce after 2009.

    Ford and others are expected to employ such a system as well.

    While we have until now lagged behind our European counterparts in access to the latest diesel technologies, we will be the first with access to Blue- tec, because of our tougher emissions standards.

    The technology will subsequently be introduced to passenger cars in Europe and other markets.

    Second-stage Bluetec will appear in the R-, ML- and GL-Class models in 2008.

    All that technology won't be cheap. Mercedes has yet to announce pricing for the E320 Bluetec in Canada.

    But there's little doubt it will be more than the previous E320 CDI, which started at $75,450.

    The E320 Bluetec is a package to be coveted.

    It's smooth, quiet, fast, comfortable and hugely responsive to your right foot, not to mention clean and fuel efficient.

    This Benz gives credence to industry predictions that diesel use in North America is likely to quadruple by 2015.


    Gerry Malloy, a freelance journalist (mgmalloy@aol.com), prepared this report based on travel provided by the auto maker.


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