March 28, 2003

GM’s new 3.6 litre V6 to debut in 2004 Cadillac CTS

Warren, Michigan – An all-new 3.6 litre V6 VVT engine will make its debut in the 2004 Cadillac CTS. The V6 VVT engine is the first V-6 engine program to address what Thomas G. Stephens, group vice president, GM Powertrain, says is a vital initiative: to develop world-class engines with fully contemporary features — such as dual overhead cams and variable valve timing — but at a competitive cost structure that allows use of the engines in a global mix of vehicles.

The 2004 3.6 litre V6 VVT engine is the first variant of the global V6 engine family to go into production. Although a design priority was to minimize or even eliminate all sources of undesirable engine noise, the sound that does reach the vehicle occupants has been carefully optimized to be rich and rewarding.

Focus on reducing noise, vibration and harshness (NVH) did not compromise the dictates of high specific output. The 3.6 litre global V6 develops 255 hp @ 6,200 rpm and 252 lb-ft of torque @ 3,200 rpm.

The adoption of fully variable valve timing for both intake and exhaust valves provides flexibility, fuel economy and emissions-reduction. The four-cam variable valve timing is a key element in the V6 VVT control strategy, which imparts the engine with extreme flexibility. For example, 90 percent of the 3.6 litre V6’s peak torque is available across a remarkably broad operating range, from 1,600 rpm to 5,800 rpm.

“Flexibility was very important,” says Bob Jacques, base engine design system engineer. “We insisted on going after high performance and high refinement at the same time.”

Compared to an existing GM DOHC V6, the 3.6 litre V6 VVT develops 20 percent more peak power, a 13 percent increase in peak torque – and a 24 percent increase in torque-integral, or the amount of torque available at most points throughout the rpm range.

Key technologies include: all-aluminum construction, dual overhead camshafts (DOHC), 4-valve-per-cylinder valvetrain, roller-finger follower valvetrain, continuously variable cam phasing, electronic throttle control (ETC), durable forged-steel crankshaft, piston-cooling oil jets, coolant-loss protection software, GM’s Oil Life System, 32-bit microprocessor and coil-on-plug ignition.

The engine employs specially isolated cam covers to decouple them from vibration created by the combustion process, while the engine front cover incorporates internal damping plates to quell engine vibrations. A structural aluminum oil pan, attached by a full-circle mounting, enhances bending stiffness and mitigates “drumming” from the oil pan.

Polymer-coated piston skirts help the piston to track more smoothly and quietly in the bore. Pressure-actuated piston-oil squirters help cool the pistons, contributing to performance and durability, and help minimize noise that typically emanates from the cylinder bores and reciprocating components. “Hiss” from the PCV valve is eliminated by using two dissimilar-sized flow-metering holes, while equal-length intake manifold runners minimize half-order noise content.

The camshaft sprocket employs durable, molded-rubber “cushion rings” that absorb the noise of the camshaft drive engaging the sprocket teeth. A new oil pump design prevents noise caused by oil aeration while the fuel rail includes an internal fuel pressure damper, which attenuates the pressure pulsation in the fuel system to reduce radiated noise.

A forged steel crankshaft ensures the durability required of high specific output variants and provides an extra degree of robustness.

Flexible oil pan configurations facilitate the engine’s adaptability for all drive layouts. V6 VVT engines destined for AWD applications, for example, are fitted with an oil pan cast specifically with a pass-through so that the front-wheel half shaft can be fitted.

Three pressure-actuated piston-cooling oil-jet assemblies in the block each hold a pair of oil squirters that douse the underside of the piston and the surrounding cylinder wall with cooling oil. This practice reduces piston temperatures, which helps the engine develop more power. The cooler piston/cylinder interface also enhances long-term durability.

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