General Motors working on a second, larger twin-turbo V6?

Adding credence to earlier rumors, it appears GM may be working on a big turbo V6 to take on Ford's 3.5L EcoBoost.

An unnamed inside source at General Motors says that, in addition to the automaker's planned 3.0-liter twin-turbo V6, a 3.6-liter unit utilizing a similar number of turbos is also in development. But just what hood this larger V6 engine will slot under remains up in the air.

Leftlane reported last July that General Motors may be working on an eight-speed automatic transmission for large rear-wheel drive vehicles like its Chevrolet Silverado/GMC Sierra twins, and at the time there were early rumors hinting that a twin-turbo 3.6-liter V6 may also make its way into the 2014 GMT900-codenamed full-size trucks.

Then things get a bit tricky since it seems to make perfect sense that this engine would offer a counter to Ford's popular 3.5-liter EcoBoost (that's Ford-speak for twin turbos) used in the F-150, but there is speculation that GM's new mill won't even end up in a truck.

Rumors suggest that the 3.6-liter twin-turbo may in fact be in development exclusively for Cadillac, possibly as the range-topping engine for the ATS in the ATS-V. At the same time, however, it is probably that GM would want to spread development costs across multiple vehicles and find a way to counter Ford's EcoBoosted F-150.

As far as the power figures are concerned, GMInsideNews points out that a Chevrolet Camaro concept car with a 3.6-liter twin-turbo under the hood appeared at SEMA in 2009, claiming to have 425 horsepower and 400 lb-ft of torque. Since it was a show car, it is hard to say if those figures were accurate as they seem a bit steep, but they certainly aren't out of the question.