This Is The New, Hand-Built DOHC Cadillac V8
Chief engineer of GM's V8 engines gives us a tour of the newly unveiled twin-turbo mill at the heart of the new, 550-hp, 627 lb-ft Cadillac CT6.
Cadillac’s Jordan Lee has the best job in the world, at least as jobs exist in my own fantasyland of wish fulfillment. Lee is chief engineer of V8 engines at General Motors, which means his team gets the cool projects, like an all-aluminum, DOHC V8 that just gave Cadillac a premium-grade powerplant on par with with those of its German competitors.
Not that there’s anything terribly wrong with pushrod V8s, like those that have powered all Cadillac models since the brand discontinued production of its Northstar engine series in 2003. Cam-in-block V8s are efficient at making power, easy to package, and cheap to build. Still, double overhead-cam, four-valve-per-cylinder V8s, while more complex, breathe freer, have more power at the top end of the rev range, and have less valvetrain inertia, and thus a more premium feel befitting a luxury sedan.
At the New York auto show this year, Cadillac unveiled a 4.2-liter DOHC, twin-turbocharged V8, which will first power the CT6 V-Sport, a blustery version of Caddy’s largest sedan. Two new CT6 models will get this V8: a standard version tuned to 500 hp and 553 lb-ft, and the high-output version in the V-Sport, which creates 550 hp and peak torque of 627 lb-ft. In the CT6, the new engine will be paired with GM’s 10-speed Hydra-Matic.
In addition to the extra cams, the new engine gets a 9.8:1 compression ratio and a 5,076-psi direct-injection system. Like similar engines from BMW, Mercedes-Benz, and Audi, the new V8 has a “hot V” design, in which all of the engine’s hot-side plumbing, from exhaust manifolds and twin-scroll turbochargers—each turbo-manifold pairing combined in a single unit—and catalytic converters are packaged inside the V between cylinder heads. The benefits are more responsive turbine spool-up and easier packaging. An air-to-liquid intercooler cools the intake charge, electronically-controlled wastegates manage boost up to 20 psi, while the turbos’ titanium-aluminide turbines save weight and can spool up to 170,000 rpm.
The new engine will be hand built at GM’s Performance Build Center in Bowling Green, Kentucky, along with Chevrolet Corvette production, which has lead some to speculate on which other, say, mid-engined vehicles might wind up with this 4.2 in their engine bays. No confirmation from GM on whether or not Cadillac will share its new performance bounty.