New 4.0-litre V8 to power Mercedes-AMG GT
Mercedes-Benz has unveiled technical details of an all-new 4.0-litre bi-turbo V8 which it will be using to power its upcoming Mercedes-AMG GT sports car due to be unveiled at the Paris Motor Show later this year.
Known internally as the M178, this new engine is the latest addition to AMG’s rich history with V8s going back to the M100 of the 300 SEL 6.3, an enlarged version of the same engine in the 450 SEL 6.9, right up to more recent mills like the 6.2-litre M156 and 5.5-litre twin turbo M157 used in various “63 AMG” models.
Independently developed and produced by AMG, the M178 is based heavily upon the 2.0-litre four-cylinder found in the A 45 AMG and CLA 45 AMG – bore and stroke measurements are identical (83.0mm by 92.0mm), resulting in a 3,982cc displacement, precisely double the four-pot’s. The two engines also share a considerable amount of technology, most notably third-generation direct injection with spray-guided combustion for improved thermodynamic efficiency.
Construction of the engine is lined with materials selected to keep overall weight of the powerplant down. The closed deck crankcase is made out of sand-casted aluminium whilst surface of cylinder liners incorporate Nanoslide technology that makes them twice as hard as conventional cast iron linings. Pistons, meanwhile, are made of forged aluminium and lined with low-friction rings.
A notable process implemented in the engine’s construction process is ‘spectacle honing’, whereby he cylinder liners receive their mechanical surface treatment when already bolted in place. A jig resembling spectacles is bolted to the crankcase in place of the cylinder head mounted later. Any cylinder warpage that might occur during final assembly is therefore taken into account or eliminated as the cylinder liners are honed.
Besides blessing the engine with low weight (209kg dry), Mercedes also endeavoured to package it as compact as possible. Its pair of turbochargers sit in between the cylinder banks as opposed to outside them in the case of most turbocharged V8s. This arrangement, Mercedes claims, also have the added advantage of optimizing fresh air supply into the chargers. Maximum boost of the turbos, which spin up to 186,000rpm, is 1.2 bar.
Lubrication is circulated through a dry sump system, which enables the elimination of a conventional oil pan and consequently enables the engine to be mounted 55mm lower than it otherwise would have to be. Another advantage of dry sump lubrication is that it ensures optimum distribution of oil even under high lateral acceleration.
Thanks to its pair of turbochargers complemented by its array of technologies, the 4.0-litre M178 generates outputs comparable to the naturally-aspirated 6.2-litre M156 used in the previous-generation E 63 AMG. From 1,750 to 4,750rpm, the driver has unbroken access to 650Nm of torque, before full power of 510hp is delivered at 6,250rpm. Mercedes anticipates that the engine’s consumption will dip below 10 l/100km, ensuring compliance of Euro 6 emission standards.
Besides brute muscle, AMG also takes considerable pride from the unique sounds generated by its engines. Variable flaps incorporated into the exhaust system enable the type of sound generated by the V8 to be altered according to driving conditions. At low load, the flaps close to ensure exhaust gases flow through the rear silencer for a quiet cruise; as engine load increases, the flaps progressively open to let more noise into the cabin.
In accordance to time-honoured AMG tradition, the M178 will be handbuilt, which each engine assigned to a specific builder who will then sign off a plaque before commissioning the engine. Before being fitted into the cars they are assigned to, each engine is systematically bench-tested to ensure that they not only meet performance goals, but also able to function reliably over a variety of demanding conditions.
KON
Pictures: Official Mercedes-Benz release.
