Mercedes-AMG just broke our heads with the M139, a 416 hp 4-cylinder engine

Not so long ago, four-cylinder turbocharged engines rarely developed more than 250 horsepower. But these days are over, and just in case you need to convince, here is the latest four-cylinder Mercedes-AMG: the M139, announced Thursday.

The S M139 is now officially the world's most powerful four-cylinder engine with 416 hp. No, it is not a typo; this four-cylinder 2.0-liter makes more power than the 4.4-liter V8 engine of the BMW E9x M3 made. This also generates a lot more torque, around 369 foot-pounds, to be exact. There is also a non-S version, which makes 382 horses, but we do not care!

"With the M139, we have once again impressively demonstrated Mercedes-AMG's expertise in engines," Mercedes-AMG President Tobias Moers said in a statement. "Not only is the efficiency per liter unmatched for a supercharged engine, but its high efficiency also demonstrates that the internal combustion engine still has additional potential."

The M139 engine is different from his predecessor, the M133in many ways. The most important change is that the engine has been turned over so that the exhaust side of the cylinder head is directed towards the vehicle firewall. This simplifies the piping routing of the turbo system and allows AMG engineers to lower the nose of the car to improve aerodynamics.

The AMG engineers did not stop there. They have equipped the M139 with a highly efficient (and expensive) double ball bearing turbo. This has the effect of increasing turbo responsiveness and eliminating the latency that would normally be expected in such a highly supercharged engine.

Another concern created by all this turbo pressure – almost 30.5 pounds per square inch, to be exact – is whether the internal components of the engine will be able to withstand its abuse for a long time. To remedy this, Mercedes chose to use a closed-deck engine block for cylinder stability, as well as a crankshaft and forged pistons, both lighter than their cheaper cast counterparts.

AMG uses a number of other tips to increase engine longevity and power, including an electric water pump that reduces spurious losses and can be more precisely controlled to manage engine temperatures. She also opted for air-to-water intercooling, rather than the more traditional and less expensive air-to-air style. This has the advantage of better packaging and greater stability for the engine under load thermals.

It's clear that the M139 does not need more than 400 horses, but because AMG apparently only employs crazy people who do not live in the same world as you and me, it does it anyway. We do not know yet in which engine Mercedes will install this engine – we would guess things with a badge "45" followed by a small "s" – but it will undoubtedly be a riot in all applications.