The last place one would expect to find devotion to a two-decade-old, iron-block six-cylinder engine is Volkswagen. The company has developed a line of powerful turbocharged, direct-injected four-cylinders, but VW remains committed to an aging engine that defies easy categorization: the VR6.
We -- like VW itself -- have occasionally described the VR6 as a V-6, but that's not strictly correct. Whereas most V-6s use two separate cylinder heads, the VR6 uses a single head. It's not an in-line six, though, because the cylinders are staggered and separated into two narrowly angled banks of three cylinders (15 degrees when the engine was first introduced).
In German, as in English, the V indicates an angle between two cylinder banks. Whereas we'd call a straight six an I-6, the Germans call it an R-6, with R standing for Reihenmotor. VW simply combined the two terms, resulting in the name VR6, which, loosely translated, means in-line V-6.
The benefits of this staggered, narrow-angle layout are clear: the VR6 is only marginally longer and wider than a four-cylinder engine, meaning that it can be mounted transversely in small front-wheel-drive cars without the need for a long, space-wasting hood. Volkswagen began work on a prototype 2.0-liter VR6 in 1978, but by the time it entered production in 1991, the VR6 had grown to 2.8 liters, largely to meet the needs of power-hungry Americans. The VR6 made its debut in the Passat and shortly thereafter found a home in the Corrado sport coupe. From there, it proliferated into other VWs, including the GTI and the Jetta.
With two valves per cylinder, the original VR6 developed between 172 and 178 hp, depending on the application. But it wasn't this engine's output that characterized it -- it was the VR6's sound and smoothness. Indeed, the VR6's refinement matched the best in-line sixes'.
Even though the engine's plastic cover said DOHC, the original VR6 was functionally an SOHC design, with each cylinder's valves actuated by the same camshaft. In 1999, a 24-valve variant was born, also with two camshafts in total, but now one operated all the intake valves while the other opened all the exhaust valves. Variable valve timing was now possible, helping broaden the VR6's torque curve.
All these advantages bring up the obvious question: why have no other makers followed VW with VR engines? Mainly, the tightly packed cylinder head imposes severe compromises in combustion-chamber and port designs. Even within VW, the VR6 is gradually giving ground to the turbocharged 2.0T four-cylinder, which produces more power and uses less fuel. But Volkswagen insists that the VR6, having now been increased in size to 3.6 liters and with a smaller included cylinder angle of 10.6 degrees, will continue to power the CC as well as the forthcoming new Passat, Touareg, and Porsche Cayenne.
The VR6 is nearly as compact as a four-cylinder, but thanks to turbocharging, the current 2.0T is more powerful and more efficient than the VR6.