Meet Cadillac's 400-hp V-6 Engine

General Motors Co.'s Cadillac unit has unveiled a 3.0-liter V-6 engine that makes 400 hp and 400 lb-ft of torque.

Cadillac Chief Engineer Dave Leone says the twin-turbocharged mill sets a new benchmark for power density: 133 hp per liter. He boasts the engine is the only production 6-cylinder unit to combine two-cylinder deactivation and automatic stop-start technology. GM expects the combination to improve fuel efficiency 6%.

The twin-turbo system uses low-inertia titanium-aluminide turbine wheels that reduce rotating inertia by more than 50% compared with conventional Inconel turbines. A single throttle body controls the air charge from both turbochargers, reducing complexity and enhancing torque response. Peak torque is available between 2,500 rpm and 5,000 rpm.

A patented, water-cooled charge-air system built into the intake manifold reduces turbo lag with an air flow routing volume that is 60% smaller than a conventional design with remotely mounted heat exchanger. GM says the configuration lowers air charge temperature more than 200 F.

The 3.0-liter powerplant will be mated to the Hydra-Matic 8L90 8-speed automatic transmission that debuted in the 2015 Chevrolet Corvette.

GM also is introducing a fourth-generation version of its naturally aspirated 3.6-liter V-6 engine in the CT6. The redesigned engine is rated at 335 hp and 284 lb-ft of torque. Like the twin-turbo powerplant, the larger engine includes two-cylinder deactivation and stop-start technology. The combination is expected to improve fuel efficiency about 9% compared with the current-generation engine.

Both engines share stiffer aluminum blocks, polymer-coated pistons, a four-cam phasing system, redesigned cylinder heads with integrated exhaust manifolds and an all-new two-stage electric oiling system housed inside the block for quieter operation.

The 3.6-liter engine will be mated to a new Hydra-Matic 8L45 8-speed automatic transmission. The unit shares its architecture with the brawnier 8L90 gearbox but weights 30 lbs less. It also occupies the same space as the previous 6-speed gearbox.