GM Unveils New 400-horsepower Twin-turbo V6 For Cadillac CT6

A 3.0-liter twin-turbo, direct-injection V6 featuring cylinder deactivation and start/stop technologies will debut in the new 2016 Cadillac CT6 performance sedan at the upcoming New York Auto Show.

The engine is based on a clean-sheet, next-generation line of General Motors DOHC V6 engines that also includes a 3.6-liter naturally aspirated version that will replace the engines in the current ATS and CTS models as well as being offered in the new CT6. GM didn’t release final performance numbers but estimates the twin-turbo V6 will offer 400 horsepower and 400 lb-ft peak torque, which equates to 133 horsepower per liter. By comparison, the BMW 3.0-liter twin-turbo in the 740Li is rated at 315 horsepower, and the Audi 3.0-liter supercharged V6 is rated at 310 horsepower.

The new twin-turbo V6 will be backed by the Hydra-Matic 8L90 8-speed transmission. Helping boost low-end torque is a pair of low-inertia turbos that GM says sustains peak torque from 2,500 to 5,000 rpm.

“Torque is the pulling power of an engine and the new 3.0L Twin Turbo delivers it with confidence-inspiring smoothness and progression,” says Rich Bartlett, assistant chief engineer. “In fact, the potency of the torque across the rpm band is matched only by the satisfaction of the horsepower created as those revs climb quickly to 6,500 rpm.”

The cylinder deactivation feature kills one cylinder on each bank during low-load conditions to help save up to six percent on fuel. The start-stop technology also reduces fuel consumption by turning off the engine when the vehicle is stopped, then automatically restarting when the driver releases the brake.

GM’s 4th-generation V6 lineup features a stiffer aluminum block, forged-steel crankshaft, polymer-coated pistons and sinter-forged connecting rods. There’s also a new patented cooling system that “targets” the engine’s hottest areas while fostering a faster warm-up. The cylinder heads also received a makeover with integrated exhaust manifolds. Other improvements include a quieter cam-drive system and 2-stage oil pump.

Both engines share a 85.8-mm stroke but the 3.0-liter has a smaller 86-mm bore that reduces the piston weight for improved rev capability and opens up the coolant passages between cylinders.

“With nearly zero turbo lag and a commensurately low-inertia rotating assembly, this engine climbs the rpm ladder and produces power on demand,” says Bartlett. “Its performance is more than just the maximum output – it’s how it is delivered.”

Other twin-turbo features of note include 9.87:1 compression ratio compared to 11.5 on the 3.6; the pistons have steel insert on top ring land to handle higher cylinder pressures; and the valves are held at 19 degrees on the intake side and 16 degrees on the exhaust side, compared to the 3.6L’s 18 degrees for the intake and 15 degrees for the exhaust.

The turbos feature titanium-aluminide turbines that reduce the rotating inertial load by more than 50 percent over conventional Inconel materials. Max boost is up to 18 psi. The engine also features an integrated water-to-air intercooler that lowers the air-charge temperature by more than 200 degrees F.

“It is a very short path from the compressors to the intake ports,” says Bartlett. “The compressors draw their air directly from the inlet box and send their pressurized air through the intercooler immediately for a tremendous feeling of power on demand.”

Both engines will be assembled at the Romulus Powertrain Operations plant near Detroit.

About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World.
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