This is the 503 hp Mercedes AMG GT engine

New twin-turbocharged 4-liter AMG V8 also packs 479 lb-ft of torque

 AMG 
The new Mercedes AMG GT supercar will get a twin-turbo V8 making 503 hp and 479 lb-ft of torque. 

The eagerly awaited Mercedes-AMG GT will be powered by a twin-turbocharged four-valve-per-cylinder 4.0-liter V8 gasoline engine that produces 503 hp (SAE) at 6,250 rpm and 479 lb-ft of torque between 1,750 and 4,750 rpm in its initial state of tune, the German car maker has officially confirmed.

The all-new 90-degree quad-cam direct-injection unit, known internally under the codename M178, has been developed from the ground up as a replacement for AMG's existing naturally aspirated 6.2-liter V8, the M159, which is being phased out after four years following the end of production of the SLS AMG in both coupe and roadster guises.

AMG's new sand-cast aluminum-block engine is also slated to power the upcoming replacement for the C63 AMG. It boasts the same 83 mm (3.2-inch) and 92.0 mm (3.6-inch) bore and stroke measurements as the Mercedes-Benz performance car division's highly strung 355 hp turbocharged 2.0-liter four-cylinder direct injection powerplant, as used by the CLA45 AMG; overall swept volume is 3,982 cubic centimeters, or 243 old fashioned cubic inches.

 AMG
The new Mercedes AMG GT engine on the test stand.

Boosting induction are a pair of Borg Warner-produced turbochargers mounted atop the engine within the space between the two cylinder banks -- a layout AMG engine boss Christian Enderle says helps make the M178 some 3.5 inches shorter than the M159 engine. The turbochargers, which operate in a parallel state at a maximum pressure of 33 psi, are cooled by a water-to-air intercooler.

Other technology included on AMG's second turbocharged production car engine is a Bosch-supplied piezo injection system capable of providing up to seven individual injections per cycle, cylinder barrels finished with Mercedes-Benz's patented Nanoslide friction-reducing material, a cylinder head produced from a lightly Zirconium-refined aluminum, and dry-sump lubrication.

The exhaust is rooted from the turbochargers high up in the middle of the engine, providing the M178 with what is known as a “hot inner vee.” Initial aural impressions of the new powerplant on a test bed at AMG's headquarters in Affalterbach, Germany, reveal it retains the characteristic baritone exhaust note possessed by its predecessor.

 AMG
The new Mercedes AMG GT will have 503 horsepower when the car launches.

With a specific output of 126.3 hp per liter, the turbocharged M178 engine slated for the new GT develops a significant 35.6 hp more per liter than the naturally aspirated M159 unit fitted to the standard SLS AMG. But with a swept volume that is a considerable 2.2 liters less than its predecessor, its overall 503 hp is down by 65 hp on the engine it replaces in its initial state of tune. Peak power is also developed 750 rpm earlier in the rev range at 6,250 rpm.

The new AMG engine's 479 lb-ft of torque is the same as that offered by the standard M159 unit. However, it is developed 3,000 rpm earlier in the rev range at 1,750 rpm and continues on a plateau through to 4,750 rpm.

By comparison, BMW M division's twin turbocharged 4.4-liter V8 direct-injection gasoline engine, as used by the M5, M6 coupe and M6 cabriolet, boasts 125.6 hp per liter for an overall 552 hp at 6,000 rpm and 501 lb-ft of torque from 1,500 through 5,750 rpm.