• Cylinder deactivation temporarily deactivates two of the cylinders in light-load driving conditions to enhance efficiency and seamlessly reactivates them when the driver demands full power.

• With the stop/start system, the 3.0L Twin Turbo is shut down in certain driving conditions such as stop-and-go city driving to reduce fuel consumption, automatically restarting when the driver takes his or her foot off the brake pedal.

Peak output is estimated at 400 horsepower (298 kW) and 400 lb-ft of torque (543 N·m), making it one of the most power-dense V-6 DOHC engines in the world, developing 133 horsepower (99 kW) per liter.

The 3.0L Twin Turbo is coupled to the Hydra-Matic 8L90 eight-speed automatic transmission.

Similar to the turbo system in the track-capable Cadillac ATS-V, the new 3.0L Twin Turbo features turbochargers with lightweight, low-inertia titanium-aluminide turbine wheels and an efficient, patented low-volume charge-air cooler, which contribute to optimal boost production and more immediate power delivery.

The advanced, low-inertia turbochargers enable the engine to sustain peak torque from 2,500 rpm to 5,000 rpm, giving it a broad torque curve that is conveyed to the driver through a feeling of responsive, sustained power across the entire rpm band.

The 3.0L Twin Turbo’s estimated 400 horsepower and 133 hp per liter is 27% greater than the BMW 740 Li’s 3.0L turbocharged I-6 (315 hp and 105 hp/L) and 29% more than the Audi A7’s 3.0L supercharged V-6 (310 hp and 103 hp/L). The 3.0L Twin Turbo is up to 5 dB quieter than the Audi 3.0L TFSI engine, while the 3.6L is up to 4 dB quieter than the Infiniti 3.7L V-6, GM said.

All-new V-6 architecture. Cadillac’s new 3.0L Twin Turbo is part of a new generation of technologically advanced V-6 engines, which includes a new version of the award-winning 3.6L naturally aspirated engine employed for years across the brand’s model range. Each features all-new structural and combustion elements designed to complement higher performance and greater efficiency with exceptional quietness and smoothness.

Features shared by the 3.0L Twin Turbo and 3.6L include:

• Stronger, stiffer aluminum block with increased structure in the bulkheads for superior rigidity;

• Tough, refined rotating assembly with a stiff forged-steel crankshaft, friction-reducing polymer-coated pistons and strong high-copper-content, sinter-forged connecting rods;

• New four-cam phasing system with intermediate park technology that enhances efficiency by enabling late inlet valve closing in certain conditions;

• All-new, patented “targeted” cooling system that provides strategic cooling of the engine’s hottest areas while simultaneously fostering faster warm-up, which enhances efficiency;

• New cylinder heads that enhance combustion performance and include direct injection and feature integrated exhaust manifolds;

• Revised, simplified timing drive system with cushioned chain sprockets contributing to quieter engine operation; and

• All-new oiling system moves the pump inside the block for quieter operation. The two-stage oil pump also enhances efficiency.

Continuously variable valve timing with intermediate park feature. Camshaft phasing allows the greatest variances in valve timing to make the most of power and efficiency. The new engines takes that technology to the next level with intermediate park technology for the intake camshaft phasers.

Because optimal part-load efficiency requires retarding the intake cams to reduce pumping losses, the effect also reduces the effective compression ratio, which affects the engine’s cold-start performance. Conventional cam phasing system authority is limited by how far the intake cams can be retarded in the parked position without affecting cold starting.

Intermediate park technology, which incorporates an intermediate-lock intake variable valve timing cam phaser, allows the cams to be parked at the most favorable position for cold starting, while expanding the amount of intake cam retard for other conditions by adding another 20 degrees of intake phaser authority. This enhances fuel efficiency and reduces emissions.

Targeted cooling system. Unlike conventional systems, which force coolant flow from the front of the block to the back, the new patented targeted cooling system sends coolant simultaneously to each water jacket in the heads and block.

This new, parallel-flow design maximizes heat extraction in the area of the upper deck, intake and exhaust valve bridges in the heads and integrated exhaust manifold with a minimal amount of coolant. The result is more even and consistent cooling, which enhances performance, and faster engine warmup, which improves cold-start efficiency and reduces emissions.

Additionally, the strategic sizing of the coolant jackets in the head and the block reduces the cooling system thermal inertia, allowing the use of a smaller water pump, which requires about 50% less power to drive, enhancing fuel efficiency and even allowing a lower overall height of the cylinder block.

New cylinder head design. An all-new cylinder head design builds on the airflow attributes of the current V-6, supporting a broader power band that ensures excellent low-rpm torque, for strong power at take-off, and excellent airflow at high-rpm, for greater horsepower.

Engineers achieved that through increased in-cylinder mixture motion, a faster burn rate of the air-fuel mixture and attributes that took full advantage of the new intermediate park cam phasing system.

Highlights include:

• The intake valves are 6% larger, resulting in a 5% increase in flow capacity and a significant 25% increase in in-cylinder mixture motion;

• The exhaust valves are also 6% larger, for a 10% increase in flow capacity;

• The injector angle was increased from 22 degrees to 24 degrees, which helps reduce emissions and oil dilution;

• The adoption of a smaller, 12mm spark plug (vs. the previous 14mm plug) allows it to be more centrally located in the cylinder for improved flame propagation and greater light-load efficiency; and

• A combustion chamber design to promote in-cylinder mixture motion, achieve a faster burn rate and increase dilution tolerance to take full advantage of the intermediate park cam phasing system.

The new head design also has improved combustion chamber cooling enabled by the patented targeted cooling system, which reduces the chance for knock and enhance high-load efficiency.

An integrated exhaust manifold rounds out the head’s features, saving weight over a conventional, separate head/manifold assembly.

3.0L Twin Turbo. While the 3.0L Twin Turbo is based on the same, all-new architecture as the naturally aspirated 3.6L V-6, it incorporates specific components and features to support the load and cylinder pressure characteristics unique to a forced-induction engine.

Its 86mm bore specification is about 10% smaller than the 3.6L, while both engines share an 85.8mm stroke. The smaller bore reduces the size and consequentially the weight of the pistons in the 3.0L Twin Turbo, making the most of the rotating assembly’s geometry to match the quicker rev capability enabled by the low-inertia turbochargers’ quick spool-up.

The smaller bores also allow larger water jackets between the cylinders, which helps maintain optimal combustion temperatures across the rpm band and during sustained high-load, max-boost performance.

Additional features unique to the 3.0L Twin Turbo include:

• Lower 9.8:1 compression ratio vs. 11.5:1 on the naturally aspirated 3.6L;

• Extreme duty 44MnSiV6 steel crankshaft forging;

• The pistons incorporate a specific steel insert in the top ring land to support the turbocharged engine’s higher cylinder pressures;

• Large, 36mm intake valves and 29mm sodium-filled exhaust valves enable the engine to process tremendous airflow;

• The valves are held at 19 degrees on the intake side and 16 degrees on the exhaust side vs. the 3.6L’s 18 degrees for the intake and 15 degrees for the exhaust;

• Valve spring pre-load tension is increased to manage the greater exhaust pressure during peak load performance;

• Hardened AR20 valve seat material on the exhaust side is used for its temperature robustness, while the heads are sealed to the block with multilayer-steel gaskets designed for the pressure of the turbocharging system; and

• Tuned air inlet and outlet resonators, aluminum cam covers and other features contribute to exceptional quietness and smoothness.

Low-inertia turbochargers and vacuum-actuated wastegates. The twin, low-inertia turbochargers’ featherweight titanium-aluminide turbines are used with vacuum-actuated wastegate control for precise, responsive torque production. The titanium-aluminide turbines reduce rotating inertial load by more than 50%, compared with conventional Inconel turbine wheels. That means less exhaust energy—which spins the turbines—is wasted in stored inertial loads.

In practical terms, that means the relatively small size of the turbochargers and their lightweight turbines foster more immediate “spooling,” which practically eliminates lag, for an immediate feeling of power delivery. They produce up to 18 pounds of boost (125 kPa).

A single, centrally located throttle body atop the engine controls the air charge from both turbochargers after the temperature is reduced in the intercooler. This efficient design also contributes to more immediate torque response, while reducing complexity by eliminating the need for a pair of throttle bodies.

Unique vacuum-actuated wastegates—one per turbocharger—are used with the Twin Turbo for better management of the engine’s boost pressure and subsequent torque response for smoother, more consistent performance. They are independently controlled on each engine bank to balance the compressors’ output to achieve more precise boost pressure response.

The wastegates also work in concert with vacuum-actuated recirculation valves to eliminate co-surge from the turbos—a condition that can result in dynamic flow reversal, such as the moment immediately after the throttle closes. This overall system integration contributes to the engine’s smoother, more consistent feeling of performance.

Patented low-volume charge-air cooling. Cadillac’s patented, manifold-integrated water-to-air charge cooling system also contributes to more immediate torque response, because the compressors blow through very short pipes up to the intercooler.

With no circuitous heat-exchanger tubing, there is essentially no lag with the response of the turbochargers. Airflow routing volume is reduced by 60% when compared with a conventional design that features a remotely mounted heat exchanger.

It is a very short path from the compressors to the intake ports. 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.

—Rich Bartlett, assistant chief engineer

The charge-cooling heat exchangers lower the air charge temperature by more than 200 ˚F (94 ˚C), packing the combustion chambers with cooler, denser air for greater power. Also, the air cooler system achieves more than 80% cooling efficiency with only about 1 psi (7 kPa) flow restriction at peak power, which contributes to fast torque production.

Manufacturing. Both of Cadillac’s new V-6 engines will be produced at GM’s Romulus Powertrain Operations assembly facility, near Detroit, which received a $540-million investment to build the next-generation V-6 engines.