DETROIT – Cadillac will fill the gap between the naturally aspirated, 3.6-liter CTS and supercharged CTS-V with a 420-horsepower, 430 pound-foot twin-turbo 3.6 V-6 engine. The new engine will be officially unveiled at the New York International Auto Show later this month and premiers in the 2014 Cadillac CTS that goes on sale this fall. The new engine is the highest-output V-6 in General Motors history; its specific output of 118 horsepower per liter trumps BMW’s twin-turbo 4.4-liter V-8, which makes just 91 horsepower per liter.
Though it’s based on the standard 3.6, the twin-turbo V-6 is virtually all new, with more than 90 percent new parts thanks to the need for stronger components to handle additional torque and power. It will be coupled to an Aisin eight-speed automatic that also will be standard with the naturally aspirated, rear-drive ’14 CTS. It’s GM’s first eight-speed transmission.
The all-wheel-drive naturally aspirated 3.6 sticks with the six-speed automatic. Cadillac will make the twin-turbo available as an option on the ’14 XTS, but with a six-speed automatic. In the XTS, the engine is rated 410 horsepower and 370 pound-feet.
The new engine tops a lineup that begins with the 2.0-liter turbo four in the new CTS, where it gets a torque boost to 295 pound-feet. That engine will be coupled to the six-speed automatic in the new Caddy midsize luxury sedan. The 3.6-liter naturally aspirated V-6 will make 321 horsepower in the 2014 CTS.
Features of the twin-turbo include a vacuum-actuated wastegate control, high-capacity air-cooler and high-pressure gas direct-injection. Compression ratio is a high 10.2:1. The dual-overhead cam engine has independently variable valve timing. With the new eight-speed, the rear axle ratio drops from 3.27:1 for the naturally aspirated V-6 to 2.85:1. Cadillac does not have EPA fuel mileage estimates yet, but says highway mileage will be well into the 20s, and it will avoid the gas-guzzler tax.
Cadillac is claiming the engine for its own, and says that despite the powertrain’s relatively compact dimensions, it doesn’t fit easily into other applications. On the other hand, as we’ve reported before, the new Cadillac CTS is being built on a longer-wheelbase version of the ATS’s Alpha platform, and the longer-wheelbase Alpha also is planned for the next Chevrolet Camaro.