Touareg slammed with torque: VW's V-10 TDI diesel delivers 750 Nm of pavement peeling power to this classy SUV

Automotive Industries, August, 2004 by Rob Wilson

"Squirt" has been defined as the effect produced by dropping ah anvil on ah open tube of toothpaste. The V-10 TDI-powered Touareg has squirt, plenty of it thanks to the best-in-class torque of 750 Nm (553 ft. lbs.) at 2,000 rpm. Power output is 230 kW (310 hp) at 3,750 rpm.

There is no fuel economy vs. performance issue here. With the standard 100 L (26.3 gal.) fuel tank, the 5.0L V-10 TDI powered Touareg will give owners a 600-mile highway cruising range at 23 mpg. And there will be people who buy it for the fuel economy, which is attractive, but most will drive it for the nimbleness of its performance. The only thing that doesn't move on this SUV package is the fuel gauge.

Al asked Stephan Krebsfanger, product development manager, Volkswagen of North America, what he felt was most important about the engine. "To us it's the combination of sheer power and luxurious, low NVH driving characteristics. This engine is being shared between the Phaeton and the Touareg in Germany and the Touareg in Germany, the U.S. and the test of the world.

"It's ah engine that has to basically please two worlds. The world of luxury, the very epitome of luxury as is expected in a sedan like the Phaeton and to have the sheer torque and brute power that you need in the world of the SUV. Bringing those two worlds together is what has been accomplished with this engine."

With a top speed of 130 mph, the V-10 accelerates the 5,825-pound Touareg from 060 mph in 7.5 seconds. Touareg towing capacity is given at 7,716 pounds.

It's all about the engine, this very novel V-10 which is comprised essentially of two inline 5-cylinder engines, Siamese twins, each with its own air intake, exhaust and turbocharger, are connected only at the crankshaft and through the electronic controls. They do, of course, share a common block and crankcase. The cylinder bank centerlines are offset by 90 degrees.

This cylinder layout results in an extremely compact engine design that contains ten 0.5L cylinders within 544 mm of overall engine length. Bore and stroke of the engine are 81.0 X 95.5 mm. This slightly undersquare design is favored for desired torque characteristics. Cylinder spacing is given at 88 mm.

In keeping with the well-defined symmetry of the cylinder layout, the firing order is such that opposing cylinders of each bank follow one another. Thus, the firing sequence is 1-6-5-10-2-7-3-8-4-9. Being a four-cycle diesel, five cylinders tire every 360 degrees of crankshaft rotation, or one combustion event for every 72 degrees, providing extremely smooth delivery of power to the Touareg's Tiptronic equipped six-speed automatic flora ZF.

Containing the violent combustion forces of a diesel is always a challenge and VW has met that challenge with unique engine architecture. The block and heads are of lightweight hypereutectic aluminum alloy.

The bottom side of the block carries the top member of a cast iron bearing tunnel. An underslung aluminum alloy crankcase carries the bottom half of the bearing tunnel. The bearing tunnel, of course, contains the crankshaft and has six main bearings.

Studs extend from the top side of the tunnel up through the block and heads, which are secured with these studs. So the studs effectively tie the combustion forces from the engine down to the reinforcing bearing tunnel. There are 12 studs per head, in effect, four per cylinder.

Cylinders are parent bored but plasma coated with a few tenths of a millimeter coating to give the cylinder surface tool steel hardness and great durability.

There are two schools of thought with respect to linered- vs. parent-bored cylinders for diesel engines. While some still regard linered cylinders to be more durable and rebuildable, others regard them as a Band-Aide on manufacturing processes. If you can hold manufacturing tolerances tightly enough, parent bored is simpler, requires fewer components, facilitates tighter packaging and more effective cooling.

Riding in these parent-bored cylinders, aluminum pistons have a sombrero-shaped entrant bowl and cast-in cooling channel, which is jet cooled with the piston at bottom dead center.

Strengthened with brass bearings, piston pin bosses and connecting rods, small ends have a trapezoidal shape and thus more bearing surface area to absorb combustion forces, a premium engine feature. Connecting rods are fabricated from sintered metal and feature an angled split on the big end. Another interesting feature is an offset pin bore. This causes the piston to shift in the opposite cylinder wall just before top dead center greatly reducing piston slap (aka: noise).

NVH is an issue in all vehicles today, but needs a bit more attention in a diesel. The V-10 TDI is fitted with a counter-rotating balance shaft operating at crankshaft speed and there are counterweights on the crankshaft webs to reduce first order vibrations.

With the 90 degree layout and offset crank throws, second-order vibrations are reduce. The crankshaft also has a viscous type torsional vibration damper. Engine oscillation is held to a few thousandths of a millimeter.