There were times when four-pot engines were loathed for their lackluster character and underwhelming performance. While the American market only ever entertained the idea either for fuel economy or for meeting emissions targets, Europeans, on the other hand, were exploring its full potential. From Porsche to BMW, there are a great many four-cylinder engines that are devised with performance in mind.

One such engine that could give a Chevy small-block a run for its money is the Mercedes-AMG’s 2.0-liter turbocharged inline-four. Internally called the M139, this engine is far from your normal turbo-four. Mercedes-Benz has put a lot of effort into developing this 416 horsepower brute. That’s right, the M139 delivers over 400 horsepower, with a specific output of 104 hp per cylinder!

Since the days of gasoline engines are numbered, we must embrace the best of the motoring world. Carmakers have been burdened with emission targets, and regulatory agencies are wasting no time and making the norms even tighter. But kudos to Mercedes-AMG for pushing the engineering limits and making four-bangers as exciting as this.

We dive into the specifics of Merc’s M139 motor and discuss why it’s the most badass four-cylinder ever made.

Mercedes-AMG M139: The Most Powerful Four-cylinder Engine In Production

Mercedes M139 Engine at the AMG assembly line
Via: Mercedes-Benz

Folks at Affalterbach have created a gem of an engine with the M139. Aside from the ridiculous amounts of power, the level of engineering that went on to create this masterpiece is truly astonishing. Let’s talk numbers. The M139 2.0-liter turbocharged inline-four is available in two states of tune.

In the base version, power is rated at 382 horsepower at 6500 rpm and 354 lb-ft from 4750 to 5000 rpm. The higher output version delivers 416 horsepower at 6750 rpm and 369 lb-ft from 5000 to 5250 rpm, thanks to increased boost pressure.

Mercedes-AMG CLA45 S - Front
Via: Mercedes-Benz

The M139, as opposed to its predecessor, the M133, revs to a 7200 rpm redline, which is 500 more than the unit it replaces. Like all AMG flagship engines, the M139 is hand-built at AMG's engine factory in Affalterbach, Germany. The all-new powertrain can be seen powering the AMG A45, CLA45, the all-rounded GLA45, and the upcoming GLB45.

Also, all future mid and top-level AMG models will likely feature the M139 with electric assistance, and the infamous twin-turbo V8 will eventually be discontinued. The new C63 AMG has already transitioned to the gasoline-hybrid setup, with a longitudinally arranged M139 sitting under the hood.

RELATED: 2020 Mercedes-AMG CLA45 S: The World’s Most Powerful Compact Sedan

Mercedes-AMG M139: Let’s Talk Engine Design

Mercedes M139 engine at display during its unveil
Via: Mercedes-Benz

It’s no surprise the engine is an extraordinary piece of kit. But how did Mercedes-AMG design a compact engine to withstand extreme temperatures and thermal stresses? Merc’s M139 engine houses a forged steel crankshaft and forged aluminum pistons.

The cylinder linings have little to no friction thanks to AMG’s Nanoslide cylinder coating that allows for a mirror-like finish. The M139 uses both Direct and Port fuel injection necessary for achieving the high specific-output figures. In the first stage, direct injectors supply fuel to the combustion chambers, and when needed, solenoid-operated port injectors supplement the system.

Mercedes-AMG M139 Engine at display
Via: Mercedes-Benz

The M139 is still a transversely mounted motor, however, it’s reverse inclined. This means the intake system sits at the front (next to the bumper), while the exhaust manifold and turbocharger sit at the rear (ahead of the passenger compartment). This results in a flatter front section, enabling engineers to design shorter air intake and exit ducts to better package the engine.

The twin-scroll turbocharger now comes with roller bearings that reduce mechanical friction, allowing the impellers to spin quickly. In addition to oil and water cooling, details like the ducted engine cover borrowed from the AMG GT’s V8 help keep the turbo housing cool by acting as a wind deflector.

The M139 utilizes a closed deck structure and a cast aluminum block that’s denser and stronger, thanks to an innovative production process. As a result, the M139 can withstand higher peak combustion pressures.

RELATED: These Are The Most Powerful Four-Cylinder Cars Ever Made

Is The Mercedes-AMG M139 Engine Future-proof? Probably Not

Mercedes-AMG-most-powerful-four-cylinder-engine-cross section
Mercedes-Benz

This high specific-output plan from Mercedes could backfire. The idea was chosen to reduce the environmental impact. However, there’s a possibility that the M139 could be killed sooner than you think. As per the EU regulation, Euro 7 supposedly restricts the use of small-displacement engines that produce higher outputs.

This includes engines like the M139 with its specific output of 104 horsepower per cylinder. That’s why Porsche is planning on introducing larger displacement engines that make relatively less horsepower. For now, they’re starting the gig with the mid-engined 718 Cayman (the GTS 4.0) and would likely be expanding to the Porsche 911.

Even the Cayenne GTS is now using a V8 instead of the V6 it previously had. This is a positive sign for enthusiasts as forced induction could take a back seat, and manufacturers might start embracing naturally-aspirated engines.

Source: Mercedes-Benz