Audi's squeaky clean 3.0 TDI engine bound for North America
Other highlights: The 90-degree cylinder block is made of vermicular graphite cast iron, which is both stronger and 15 percent lighter than ordinary iron, helping bring the total dressed engine weight in at 500 pounds. Chains driving the overhead camshafts are located at the back of the engine block to shorten the overall length of the engine to just 17.3 inches. High-energy glow plugs that reach 1800 degrees F in two seconds are used to start the engine when cold, and engineers on hand claim that on a winter morning in Fairbanks at -18 degrees F the engine took only 2.5 seconds to start (the process is automatic -- no waiting for a glow-plug lamp to go out before engaging the starter). Because diesels are slow to warm up, an electric booster provides warmth to the heater immediately after engine start-up.
The result? A 221-horsepower, 406-pound-foot engine that hustles this big honkin SUV to 60 mph in a claimed 8.4 seconds and achieves 25 mpg on the highway. How's it drive? Unlike any gasoline-powered SUV. Big thrust comes online just off idle, peaking from 1750 to 2750 rpm then tapering off as the needle approaches its modest 4600 rpm redline. Smoothly accelerating from a stop or a low cruising speed requires some right-foot finesse, or things can get jerky when the boost comes on. The V-6 gets a tiny bit coarse at higher revs too -- a problem that's utterly erased by the 326 hp, 560-lb-ft, 6.4-second 4.2 TDI V-8 or the 500-horse, 737-lb-ft, 5.3-second 6.0 TDI V-12 -- neither of which is yet slated for U.S. sales. None of the above engines suffers the noise, smell, or smoke associated with bad-old-days diesels, though they sound different at idle. The Q7 TDI's fuel economy is impressive, though recovering the price premium likely to be charged (which has yet to be announced, but will likely amount to several thousand dollars) may take way longer than the typical lease period -- especially with diesel priced 30-60 cents above regular unleaded in every state.
Still, we're bullish on diesel's future and we're thrilled to see luxury brands blazing the trail. Perhaps Mercedes, BMW, and Audi can give oil-burners an upscale, aspirational mystique that will make them more salable in Hondas, Mazdas, and other mainstreamers.