Cadillac Drops Details On All-New 4.2-Liter Twin Turbo V8 Engine

It seems the folks in the skunkworks over at Cadillac aren’t comfortable resting on the achievements of the venerable LS-series engine family in its world-beating lineup of performance luxury cars. To that end, the company revealed details today on an all-new 4.2-liter twin-turbo powerplant destined for use in the new CT6 V-Sport sedan. With two snails on board, Cadillac engineers were able to coax monster power out of the diminutive displacement powerplant, with an estimated 550 horsepower and 627 lb-ft of torque available to the driver’s right foot. In addition, there will also be a slightly-detuned 500 horsepower version of the engine platform.

Cadillac CT6 V-Sport 4.2L Twin Turbo V-8“Cadillac’s performance technology reaches new heights with the new and exclusive 4.2L Twin Turbo V-8,” said Cadillac President Johan de Nysschen. “The engineering prowess embodies the very spirt of Cadillac performance on and off the racetrack.”

The design, which uses a “hot-V” configuration that reverses the traditional engine airflow path, with air entering the cylinder heads from the lower ouside position, flows through the cylinder head into the intake valley, and into the turbochargers located at the tops of the cylinder heads, provides a number of benefits. Most importantly, it essentially drops turbo lag to zero, making for a more responsive engine, while drastically improving engine bay packaging, always a concern with engineers.

“Designing an all-new engine was the best way to achieve the performance goals for the CT6 V-Sport,” said Jordan Lee, 4.2L TT V-8 chief engineer. “It builds on Cadillac’s well-established turbocharging know-how and forges new ground with innovative features that deliver exceptional performance and refinement.”

The engine uses an all-new lightweight aluminum block with pressed-in steel liners; its 86mm cylinder bores house a forged-steel crankshaft with 90.2mm stroke dimensions. The small cylinder bores mean lighter pistons. These are constructed from hypereutectic aluminum and are equipped with a friction-reducing polymer skirt coating, all the rage today. When combined with the twin-scroll, low-inertia turbochargers,allow for quick engine response across the powerband. 36mm intake valves and 29mm exhaust valves help to scavenge the cylinders.

With up to 20 psi boost pressure on tap combined with electronic wastegates, the company says that 90-percent of peak torque is available at only 2,000 rpm and carried through 5,200 rpm. The use of twin-scroll turbochargers helps to solidify the engine’s performance, and the turbocharger housings also act as the exhaust manifolds to assist efficiency. The manifolds are also configured to work with the engine’s exhaust pulses to deliver the proper airflow to each of the scrolls in the turbos. Valve timing is tightly controlled by the ECU to help each of the engine components to work together to improve turbine efficiency and enhance exhaust scavenging.

Head-on view of engine

Another notable feature is the pair of water-cooled heat exchangers, which reside above the turbos and are cooled by their own circuit, dropping air charge temps by more than 130 degrees before the air enters one of the dual 59mm throttle bodies—one for each bank of the engine. Cadillac claims a small 1 psi drop at full power, which means torque doesn’t drop and the engine just keeps on pulling.

Alternate viewThis engine relies on all of the most advanced technologies available. Cadillac employs direct fuel injection and a 9.8:1 compression ratio, with fuel pressures topping out at an astronomical 5,075 psi. It’s delivered by a pair of camshaft-driven pumps with one on each bank. GM has also been successful with its Active Fuel Management system, which shuts down cylinders to help fuel economy when the engine is not in a high-demand situation. the engine features exclusive deactivating rocker arms are used on each of the four valves of the cylinder being deactivated.

Chain-driven dual overhead camshafts, four valves per cylinder, independent continuously variable camshaft timing are all on board. The advances made in recent years with respect to camshaft timing and the advantages it provides are well-documented; by allowing the camshafts to move independently of one another, the engine management system can be configured to maximize the torque curve of the engine without affecting drivability. The engine also features Stop/start technology designed to save fuel at stoplights, helping to boost fuel economy.

It’s apparent that the engineering wizards at Cadillac have been hard at work developing this new engine platform, and we fully expect to see them advance each of the technologies used in its design moving forward. This ain’t your Daddy’s Caddy!

About the author

Jason Reiss

Jason draws on over 15 years of experience in the automotive publishing industry, and collaborates with many of the industry's movers and shakers to create compelling technical articles and high-quality race coverage.
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