'New' diesels boost mileage, reduce soot
For the next 10 years or so very few manufacturers marketed diesel-powered cars in the United States, says Kevin Riddell, automotive analyst for J.D. Power and Associates.
"VW was a great example," he says. "They had diesel on the market for several years, and without a significant amount of advertising, they have cultivated a dedicated group of enthusiasts among their drivers who continued to buy their TDI diesel cars."
If preconceptions about diesel were a gut punch for the fuel, California's strict emissions requirements delivered the knockout.
this point, the U.S. is essentially a completely
virgin market for diesel.”
-- Philip Reed, consumer advice
Those rules, which were adopted by several other states, prohibited any new sales of the old-style diesel engines because the soot they belched turned out to be a major smog producer.
"Without California and the states that follow their rules, automakers were locked out of a huge part of the market," Linkov says.
By the 2007 model year, all but a tiny handful of new diesels were finally pulled from the market.
But that didn't mean the manufacturers were abandoning the technology. Rather, Linkov says, they were redesigning their engines to comply with the strict air pollution rules.
"At this point, the U.S. is essentially a completely virgin market for diesel," Reed says.
J.D. Power and Associates expects
Volkswagen to remain the largest global supplier
of diesel-fueled light vehicles in the coming
years, followed by Ford Motor Co. and Mercedes-Benz.
New fuel, new engines
With pioneering engine technology and a new
ultralow sulfur blend of diesel fuel -- mandated
by the Environmental Protection Agency --
which became available in most areas last
year, carmakers think this is the time to
try another push into the diesel market.
Taking advantage of the cleaner fuels, manufacturers have come up with a few tricks to make their engines clean enough to pass the California standard.
For example, Mercedes' engine
uses a urea-injection system to capture the
soot and scrub out the exhaust. The urea is
a liquid that must be replenished at every
oil change. Urea is a nitrogen-rich, synthetically
produced organic compound. Commercially it
is used as a chemical foundation for things
like fertilizer, cleaning solvents, and in
this case, exhaust scrubbers. Urea injection,
also called Selective Catalytic Reduction,
or SCR, involves squirting urea into a special
catalyst to reduce emissions of oxides of
Volkswagen took a different approach. Instead of scrubbing their exhaust with a liquid, they designed a trap that captures the particulates before they are released into the air. Then, when the trap gets near to being full, the car's computer changes the fuel mixture to run hotter and the particulate is dumped back into the engine, incinerating the pollutants.