Autobahn A8 runs between Munich and Stuttgart. The white Audi Q7 is headed for Augsburg. On a flat, straight stretch of autobahn, the tachometer is redlined at a leisurely 4200 rpm, yet the digital speedometer readout climbs to 287 kph - nearly 180 mph. That's what the world's only production twelve-cylinder diesel engine can do in a nearly three-ton SUV.
This 5.9-liter V-12 does Rudolf Diesel proud. When the engineer made this same trip more than a century ago, commuting between his mansion in Munich and the MAN research facility in Augsburg, he had to take the train, which was then pulled by a steam engine. "What a waste!" Diesel would rant. "In a year or two, my petroleum-fed compression-ignition design will ring in a new era. It's going to be three times more efficient, much more economical to run, and significantly cleaner than that noisy puff-puff device."
One hundred and sixteen years after the first patent was granted, diesel has long since become a global household name. It powers locomotives, ships, and motor vehicles; it drives factory equipment and electric generators. As far as automobiles are concerned, its most extreme variation can be found under the hood of our massive Q7. Inspired by the racing diesel engine that won Le Mans, the Audi V-12 demonstrates what can be achieved when the engineers work overtime and the accountants take a year or two off. No, this engine will never be profitable. Instead, its mission is to act as a high-tech brand enhancer. Does this burly overachiever send the wrong message for the times? Not really. Over about 2000 mostly lead-footed miles, our twelve-cylinder test car averaged a relatively impressive 16 mpg, considering its power and weight.
In the Manroland museum in Augsburg, one can still marvel at Rudolf Diesel's original work, such as his third prototype engine. Codenamed 25/40 and completed in 1896, the monstrous single-cylinder device developed 18 hp at 154 rpm - not exactly the stuff dreams are made of today. But back then, that was enough to elevate Diesel to the same elite level as Nicolaus August Otto, inventor of the four-stroke, spark-ignition gasoline engine. Both engineers were backed by powerful corporate supporters: Diesel had signed early licensing deals with MAN and Krupp, while Otto had teamed up with Deutz.