2005 Four Wheeler Of The Year

Volkswagen describes the Touareg V-10 as "the ultimate extension of the modern direct-injection diesel." We can attest that it is quiet, smooth and largely smoke-free, emitting only a brief puff of white smoke upon hard acceleration. Fuel burns cleanly due in part to an advanced fuel-injection system, using very high fuel pressure, which atomizes and precisely measures fuel as it is delivered. The injectors can deliver fuel to the combustion chambers at pressures as high as 29,733 psi.

Twin turbochargers, one for each cylinder bank, are used to maximize breathing. The turbine blades are actuated electrically for more precise delivery of cooled air, which arrives via a charge-air intercooler.

The V-10 block is aluminum, with an innovative gray cast-iron bearing tunnel into which combustion forces are introduced directly by way of the cylinder head studs. The cylinder walls are plasma-coated, a process that leaves a surface layer a few thousandths of an inch thick, helping cylinder walls resist deformation and wear.

Much attention was paid to reducing noise and vibration. The "V" configuration, with two rows of five cylinders, allows the water pump and water-cooled alternator to be located within the 90-degree valley, to be driven by shaft rather than belt. Engine oscillation caused by moving masses is limited to only a few hundred thousandths of an inch, being largely cancelled by a counter-rotating balance shaft and careful offsetting of crankshaft throws. There is a set of helical-cut spur gears at the flywheel, replacing the timing chain or toothed belt.

Keeping everything lubricated is a duplex oil delivery pump and two scavenger pumps that, according to Volkswagen, will operate reliably even at extreme angles. The result is an uncannily smooth, compact and powerful engine, EPA-rated at 23 mpg highway and 17 mpg in the city, that effortlessly powers a vehicle weighing roughly 6,000 pounds.-John Stewart