The 5.5-liter twin-turbo V-8 found in almost every 63 AMG model will be phased out starting with 2016. That’s not a surprising decision considering that the bonkers 6.2-liter V-8 was also ousted for not being in line with fuel economy levels set by modern turbocharged engines. The replacement is slated to be the internally codenamed M157, a 4.0-liter V-8, and it’s destined for engine bays across the entire Mercedes range.

Essentially a twin-turbocharged and direct-injected variant of the older 5.5-liter V-8 found in the mid-2000s on just about every "500" model, the M157 delivers between 536 horsepower and 577 horsepower in select Mercedes-Benz models sporting the "63 AMG" moniker. The only exception is the all-new Mercedes-AMG C63, which is the first "63" variant to get the new 4.0-liter, twin-turbo V-8 also found in the Mercedes-AMG GT.

The M157 was initially introduced back in 2011 on the S63 and CL63 AMG. Afterwards it was rolled out on pretty much every large Mercedes-AMG model in the lineup. Even though it offers more torque and much better fuel economy than the now-legendary M156 6.2-liter V-8, the new 4.0-liter V-8 replacement will bring even better performance and efficiency numbers, along with an improved throttle response. The last all-new model to get the 5.5-liter will be the convertible version of the S63 AMG Coupe, with its reveal being due in 2016. Every large AMG model introduced after that will get the 4.0-liter V-8 with the so-called "hot vee" positioning of its turbochargers.

Click past the jump to read more about Mercedes-AMG’s new V-8 engine.

Why it matters

Unlike the engine it replaces, the new 4.0-liter, twin-turbocharged V-8 (codenamed M177 or M178 depending on what oil lubrication system it has) is the second engine to ever be developed entirely in-house by Mercedes-AMG. With that being said, it does share some design features with the current four-cylinder engine lineup used by Mercedes-Benz. Since the powerplant is essentially two inline-four cylinders bonded to form a V-8 – with the intake runners on the outside and the exhaust-mounted turbochargers sitting inside the cylinder V – it offers a much better throttle response and improved fuel economy compared with the 5.5-liter V-8 that is about to be phased out.

The new engine is so good, actually, that even non-AMG Mercedes-Benz models will be getting a version of it when the 2017 E-Class is launched next year. With the A45, CLA45 and GLA45 AMG essentially using half of this powerplant to deliver 355 horsepower, you can probably guess that its output has been severely restricted in the new C63 and AMG GT, so there is plenty more where that came from. In other words, you shouldn’t feel too bad about the 5.5-liter V-8 being ousted by AMG, as its replacement will be much better in just about every single area.

2016 Mercedes-Benz GLE63 AMG Coupe

2016 Mercedes-Benz GLE63 AMG Coupe High Resolution Exterior
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Source: Autocar

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