Just a few weeks after detailing the 4.0-liter V-8 that will power the 2015 Mercedes-AMG GT sports car, the German automaker has revised the engine's horsepower rating. The M178 engine will offer 503 hp at 6250 rpm and 479 lb-ft of torque from 1750 to 4750 rpm. Previously, AMG said the engine would offer 510 hp.
The M178 engine uses a "hot inside V" layout, meaning both of its turbochargers sit inside the valley formed by the two banks of four cylinders. That makes the engine more compact, and also is said to improve responsiveness by cutting down the distance air must flow to and from the turbochargers. The engine also uses dry-sump lubrication, meaning its oil pan can be smaller, allowing the engine to be mounted 2.2 inches lower in the 2015 Mercedes-AMG GT to lower its center of gravity.
To cope with the 17.4-psi of maximum boost, the M178 engine has forged aluminum pistons, which are light but strong. The crankcase is made from aluminum to save weight, and the head from a zirconium alloy that is said to stay cooler. As AMG had revealed previously, the 2015 Mercedes-AMG GT gets a two-mode exhaust with flaps that open as the pilot drives more aggressively. At low speeds, one flap stays closed so all the exhaust gases are routed through additional silencers. Under more enthusiastic driving, the second flap opens and lets more engine noise out so occupants, "are left in no doubt as to the performance potential."
The 2015 Mercedes-AMG GT replaces the SLS AMG as the company's most sporting car, but the new two-seater is smaller and more affordable, so it can take on cars like the Porsche 911 and Jaguar F-Type. When European bureau chief Georg Kacher spent time with the car in Europe, he reported that it is, "virtually vice-less… It goes like stink, is comparatively affordable, and leaves loud exclamation marks on the road and track. The long-nose crowd-pleaser appears to support, assure, and occasionally even elevate the driver with every move it makes." Talking with AMG head Tobias Moers, Kacher also learned the car will have a top speed of around 194 mph and a 0-to-60-mph time below four seconds.
Although we have seen the 2015 Mercedes-AMG GT with striking green camouflage, as shown below, AMG has yet to fully reveal it publicly. That's expected to happen later this year at the Paris auto show or the Los Angeles auto show before the car goes on sale in 2015.