Detroit Diesels: Audi Q7 V-12 TDI-powered concept trumps Mercedes-Benz and BMW

Fuel cells and hybrids may have a future powering lighter sedans and trucks, but the future of the full size truck or SUV--and probably of the biggest sedans-- is diesel. They simply provide way more torque more efficiently than other modes of propulsion. They're also more expensive to produce to current emissions regs, so it's no surprise that diesel's first big push into passenger cars will be in high-end high-performance vehicles. Mercedes-Benz, Audi and BMW all announced diesel-engine production plans in Detroit, but Audi trumped them all with a concept Q7 powered by a 60-degree twin-turbo V-12 TDI that churns out 500 horsepower and 738 pound-feet of torque. Tech highlights include an iron-graphite cylinder block cast in a unique process that allows thinner walls for a 15% weight savings. The common-rail piezoelectric direct fuel injection also breaks ground with injection pressures up to 29,000 psi. It's said to be capable of launching the Q7 to 60 mph in about 5.5 seconds and returning up to 20 mpg.

No timing has been announced for the V-12, but Audi will sell a 3.0-liter V-6 diesel in 2008, producing--ahem--"only" 233 hp and 369 pound-feet of torque. It will share the Bluetec name and selective-catalytic reduction technology (which injects urea into the exhaust to reduce NOx emissions) with Mercedes-Benz, but wil NOT share any parts. Bluetec is simply a name meant to distinguish 50-state US compliant Mercedes, Audi, and VW diesels from their dirtier CDI and TDI-badged forebears. All require ultra-low sulfur diesel. Mercedes showed its previously announced GL320 Bluetec V-6 SUV (this engine also underpinned the Jeep Trailhawk concept) alongside a "concept" GL420 V-8 diesel making 290 hp and 515 pound-feet and achieving a claimed 24 mpg.

Not to be undone, BMW announced its own unique 3.0-liter twin (sequential) -turbo diesel inline six. Output is rated at 286 hp and 428 pound-feet, and it is said to be capable of whooshing a 3-series to 60-mph in 6.1 seconds. It uses the same SCR urea emissions controls as its German neighbors, but BMW didn't sign on to use the Bluetec nomenclature, which it deemed unnecessary, because BMW hasn't sold diesels in the US prior to 50-state compliance. Look for this engine to power the X5 and maybe X3 and 3-series models starting in calendar 2008.

After these image-leading brands have sold their ultra-high performance diesels for a few years, and people learn that diesels are no longer stinky slow-pokes, the way will be paved for more affordable oil-burners priced for middle-American families.