General Motors has unveiled a powerful V-6 turbodiesel that's smooth enough to debut in the company's newest luxury sedan: the '08 Cadillac CTS. It's a bold move because GM is banking on this CTS being a big hit and bolstering the reputation of its cars wearing the crest of the company's premium brand.
To avoid the problems experienced 28 years ago when GM transformed small-block gas engines into diesels, the company decided to team up with Italy's VM Motori. That's the same company responsible for the 2.8L diesel that was sold in the Jeep Liberty, but this is a totally different engine. The 2.9L V-6 appears to be based on the VMM RA 630, which has a compact design that can be installed in a longitudinal or horizontal layout, including two- and four-wheel-drive vehicles. The exhaust-gas recirculation (EGR) system is built into the heads, and the vacuum pump is built into one of the camshafts to conserve space. The 2.9L features dual chaindriven, variable-overhead camshafts to activate four valves per cylinder and can be tuned to lug at low rpm for high-torque commercial applications or programmed to run as a smooth, high-revving luxury engine.
At just 2.9L of displacement, this new diesel V-6 for the CTS makes more torque (406 lb-ft) than GM's 6.0L gas V-8 engine (373 lb-ft) used in its 1-ton trucks. While the engine can spin freely to achieve 250 hp at 4,000 rpm, the torque is available beginning at just 2,000 rpm. An electronically controlled, variable-geometry turbocharger helps make this possible.
To squeeze such impressive output from the small-displacement engine, VMM uses piezo-resistive cylinder-pressure sensors to obtain real-time data from the combustion process. This is combined with the super-accurate piezo electrically actuated injectors capable of up to eight injections per cycle and a Bosch CP3 pump providing 29,000 psi of pressure to the fuel rails. With all these weapons, the VMM engine computer is able to achieve high output while using as little fuel as possible and keeping emissions output to a minimum.