There's really nothing wrong with the 5.5-liter twin-turbo V8 that powers the current Mercedes-Benz E63 AMG, among other AMG-branded models. This engine has been praised time and again for its power, throttle response, and throaty sound. And it'll soon be phased out of the model lineup entirely after only being introduced in 2011. Fortunately, its replacement has already arrived: the new twin-turbo 4.0-liter V8 now under the long hood of the Mercedes-AMG GT.

Obviously, it's smaller than the 5.5-liter but it's capable of delivering even greater power with far better fuel economy. It's really a win-win for Mercedes. But before it's sent to engine heaven, the 5.5-liter is being called for duty in the GLE63 S Coupe which was just revealed at Detroit. It'll go up against the BMW X6M and its twin-turbo 4.4-liter V8. Bottom line is that the new 4.0-liter twin-turbo V8 will soon become AMG's main, and most likely important, engine.