Mercedes-Benz’s AMG performance division unveiled its new twin-turbo, direct-injection V-8 engine today in the S63 AMG Showcar, at its headquarters in rural Affalterbach, in the hills outside Stuttgart.
The new V-8, code-named M157, is based on the existing 5.5-liter V-8 (M273) that’s widely available throughout the Mercedes lineup. It will make its debut this fall in the S63 AMG and in the all-new, next-generation CL coupe, presumably as the CL63 AMG. Yes, that’s right: the badging will remain S63 even though the displacement will be 5.5 liters. But, really, what does that matter? Even the current AMG V-8, the M156, is actually a 6.2-liter, not a 6.3-liter, so Mercedes is just continuing its illogical badging because it wants to evoke the glories of the historic 6.3 badge.
Friedrich Eichler, head of powertrain development for AMG, explains that the new twin-turbo engine is actually rather conventional in design. “We use one turbo per cylinder bank and [rely on] very, very good volumetric efficiency [to prevent turbo lag] We also made the turbo diameter as small as possible.”
Eichler elaborates on the many changes made to the base V-8 for this new AMG application: “We changed the crankcase and a lot of geometric parts. Structural stiffness is improved, especially in the area where the crankshaft is rotating, where we made the ventilation holes smaller, for more rigidity. We have also made huge efforts toward mechanical efficiency, to reduce friction. We have roller finger followers and we have changed the pistons, the connecting rods, the diameter of the crankshaft, and the bearings. We also have a better cooling system.”
The result is an engine that exceeds the performance of the existing 6.2-liter AMG V-8 (not to mention the S600’s twin-turbocharged 5.5-liter V-12) while offering 25% better fuel efficiency. In base form, the M157 produces 536 hp and 590 lb-ft of torque; with the optional performance package, which Eichler says is the result simply of software tweaks, but ones that have been extensively tested, the M157 twin-turbo V-8 will provide 563 hp and 664 lb-ft of torque. Notably, the M157 will not be subject to the gas guzzler tax in the United States. “This engine is all about torque,” notes Eichler, and indeed the torque peak in the standard configuration is a plateau from 2100 rpm to about 4600 rpm. With the performance package, peak torque comes on at 2400 rpm and runs to about 3600 rpm.
The M157 will be mated to an updated version of the MCT 7-speed automatic transmission that debuted two years ago on the SL63 AMG. It features a wet clutch rather than torque converter. The S63 will start in second gear, with upshifts as soon as possible, in a further quest to save fuel. A standard stop/start function will also help fuel economy. AMG’s performance estimates are 4.5 seconds to 60 mph with the standard engine and 4.4 seconds with the performance package; these figures represent 1.1 to 1.2 seconds quicker times than those currently achieved by the existing S63 AMG.
The Mercedes-Benz AMG M157 twin-turbo direct-injection V-8 engine will, like all AMG engines, be built by a single mechanic at the Affalterbach facility by hand, following the AMG principle: one man, one engine.
The S63 AMG Showcar pictured here is simply a means of showcasing the new twin-turbo V-8, says Tobias Moers, AMG’s head of product development. It also mimics the Mercedes 6.3 racing sedan that put AMG on the performance-car map back in 1971, right down to the red paint and the decals. Don’t expect the S63 AMG Showcar’s 325-section rear wheels on the production car, but Moers says that the 5-spoke wheels are accurate in style.