Mercedes-Benz has finally (officially) confirmed the peak power and torque outputs of the “completely newly developed” turbocharged 2,0-litre four-cylinder petrol engine set to debut in the upcoming new Mercedes-AMG A45 hot hatch (and later roll out to the likes of the A45 Sedan and CLA45, too).

Billed as the “world’s most powerful four-cylinder engine in series production”, the Affalterbach-built powerplant will be offered in two outputs.

In flagship A45 S guise, the M139 engine will generate 310 kW (at 6 750 r/min) and 500 N.m, while in the standard A45 it will churn out 285 kW and 480 N.m. Peak twisting force in the former will be offered between a lofty 5 000 and 5 250 r/min, while in the latter will arrive between 4 750 and 5 000 r/min.

The German firm says this “increasing torque” at higher revolutions makes the engine feel “more free-revving”, while also confirming maximum engine speed of 7 200 r/min.

“We already set the benchmark in the segment with the preceding engine. This fundamentally new four-cylinder presented us with the challenge of doing even better. And we succeeded with a number of sometimes revolutionary solutions,” said Tobias Moers, chairman of Mercedes-AMG.

“With the M139, we have once again impressively demonstrated the engine expertise of Mercedes-AMG. Not only is the output per litre unrivalled for a turbocharged engine, the high level of efficiency also demonstrates that the internal combustion engine still has further potential,” he added.

Mercedes-AMG says the new engine (using a likewise new twin-scroll turbocharger and two-stage fuel injection) will be “entirely assembled by hand” on a new production line on the first floor of the engine factory in Affalterbach.

An interesting detail about the new M139 engine is that the turbocharger and exhaust manifold are now positioned at the rear, on the side of the firewall when viewed from behind. The intake system is therefore positioned at the front, allowing what Mercedes-Benz calls the “flattest possible and aerodynamically advantageous front section design”.

For increased cooling ability, an additional radiator has been added in the wheel arch to supplement the large unit in the front level of the main module.