New 45 S engine to reset the record books

Meet the world’s most powerful 2-litre four-cylinder series production engine — Mercedes-AMG’s all-new 310kW 500Nm 45 S lump set to occupy the engine bays of forthcoming A45, CLA 45 and GLA 45 models. Designed to deliver more power, less weight, better packaging and improved economy and emissions, the new M139 engine produces 285kW in standard form and 310kW in S incarnation and 490 and 500Nm respectively.

AMG promises that the new engine will deliver its torque in a peakier, more exciting manner than the outgoing units more diesel like flat curve. In other words, it will feel more like a racy normally aspirated engine. Peak torque is therefore 3200rpm further up the rev range at 5200rpm, while still producing more grunt than the old one did from 1000 to 2000rpm.

Boasting 160 bar combustion pressures, the new engine has a lighter, more robust closed deck alloy cylinder block with strengthening skirts around the cylinders, a redesigned water jacket, electrically controlled water pumps and separate coolant plumbing for the block and cylinder head. Add all-new ‘Camtronic’ variable inlet and exhaust valve control for the dual injector 16-valve head with larger exhaust valves and optimised valve seats.

A larger turbocharger now sits between the engine and the front bulkhead and brings low-friction roller bearings and an electric wastegate. The turbo is also rotated 180 degrees in order to fit the engine beneath lower bonnet lines in the new models, with additional cooling via a fan-generated engine cover, as well as oil, water and air chilling to improve under-bonnet temperature control.

Each engine is continues to be built under AMG's one-person-one-engine philosophy, but new methods and ergonomics improve the process to cut production time by a quarter and enable AMG’s four-cylinder manufacturing facility to produce 140 engines a day over two shifts. 

The all new M339 mill makes its debut in the much anticipated A45 next month with CLA 45 saloon and GLA 45 following shortly after.