New AMG M139 Engine is the Most Powerful Four-cylinder in the World

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AMG M139 Engine

AMG M139 engine offers almost 209 horsepower-per-liter, which is unrivaled among small engines.

The Mercedes-Benz AMG division is best-known for big, powerful engines, but with the rising cost of gasoline coupled with governmental pressure to constantly low vehicle emissions, Daimler’s high performance branch is looking towards the future. That future is likely to rely on small engines to go fast and with the introduction of the new M139, it is clear that AMG doesn’t have any problems making big power with a little engine.

In fact, with the 2.0-liter, four-cylinder mill offering 416 horsepower and 369 lb-ft of torque, the M139 is the most powerful four-cylinder production engine in the world while the specific output of nearly 209 horsepower-per-liter make it one of the most efficient production engines of any size from any automaker in the world.

AMG M139 Engine

Today, bring you a look at what makes the AMG M139 engine so powerful, along with a look at which vehicles will soon benefit from this powerful little engine.

High Performance Core

The cornerstone of the new Mercedes-Benz AMG M139 engine is a chill-cast aluminum block, which is constructed by pouring molten aluminum into a water-cooled mold, resulting in a particularly dense and very strong structure. This block features a closed-deck design that is borrowed from the racing world that keeps weight low and strength high, allowing this engine to stand up to extreme combustion pressure.

AMG M139 Engine

Inside of that aluminum engine block is a forged, high-strength steel crankshaft that moves the forged aluminum connecting rods and pistons. The cylinder walls are Nanoslide-coated in similar fashion to the Mercedes Formula 1 engines, helping to reduce friction and heat during combustion.

Top End

The AMG M139 engine employs a new cylinder head design that has the spark plugs and the fuel injection nozzles located in the cylinder heads for better efficiency and larger exhaust valves help to remove the hot gasses from the engine in a hurry. Those valves and the intake valves are controlled by dual camshafts mounted in the heads, of course, with Mercedes’ Camtronic variable valve timing system leading to a better combination of low-end torque and high-end horsepower.

AMG M139 Engine

As mentioned above, the M139 has fuel injector nozzles mounted in the cylinder head ports, but there is also a secondary, direct injection system that adds more fuel when boost pressures reach their peak.

AMG M139 Engine

Finally – and perhaps most significantly – the M139 features a new twin-scroll turbocharger, featuring AMG’s first application of roller bearings. That turbo is fed by a divided exhaust manifold design and the wastegate is electronically controlled, allowing for better boost pressure control. Like the twin turbo V8 in the AMG GT, the M139 uses a ducted engine cover to provide cooling air to the turbocharger in addition to the water cooling efforts.

Big Cooling System

The key to making big power from a smaller, forced induction engine is keeping everything cool and to do so, the M139 has two radiators and the intercooler unit, with all three cooling channels being controlled by a variable speed electric pump. Even the engine computer cooling is taken into consideration, with the engineers mounting it on the high-flow air filter assembly.

M139 Engine

Non-mechanical Information

The new M139 engine will first be offered in the AMG A45 hatchback, but that isn’t likely to be offered in the United States. The first vehicles to utilize this new engine in the U.S. market should be the CLA45, the GLA45 and the GLB45. In each of these vehicles, the powerful little engine will be mated to a 9-speed automatic transmission and a high performance all-wheel-drive system.

M139 Engine

The M139 will be hand-built at the AMG engine facility in Affalterbach, Germany, under the brand’s “One Man, One Engine” program. It will have its own production line in the plant and every engine will have a plaque with the name of the technician who proudly handled the build.

Photos: AMG

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"Before I was old enough to walk, my dad was taking me to various types of racing events, from local drag racing to the Daytona 500," says Patrick Rall, a lifetime automotive expert, diehard Dodge fan, and respected auto journalist for over 10 years. "He owned a repair shop and had a variety of performance cars when I was young, but by the time I was 16, he was ready to build me my first drag car – a 1983 Dodge Mirada that ran low 12s. I spent 10 years traveling around the country, racing with my dad by my side. While we live in different areas of the country, my dad still drag races at 80 years old in the car that he built when I was 16 while I race other vehicles, including my 2017 Dodge Challenger SRT Hellcat and my 1972 Dodge Demon 340.

"Although I went to college for accounting, my time in my dad’s shop growing up allowed me the knowledge to spend time working as a mechanic before getting my accounting degree, at which point I worked in the office of a dealership group. While I was working in the accounting world, I continued racing and taking pictures of cars at the track. Over time, I began showing off those pictures online and that led to my writing.

"Ten years ago, I left the accounting world to become a full-time automotive writer and I am living proof that if you love what you do, you will never “work” a day in your life," adds Rall, who has clocked in time as an auto mechanic, longtime drag racer and now automotive journalist who contributes to nearly a dozen popular auto websites dedicated to fellow enthusiasts.

"I love covering the automotive industry and everything involved with the job. I was fortunate to turn my love of the automotive world into a hobby that led to an exciting career, with my past of working as a mechanic and as an accountant in the automotive world provides me with a unique perspective of the industry.

"My experience drag racing for more than 20 years coupled with a newfound interest in road racing over the past decade allows me to push performance cars to their limit, while my role as a horse stable manager gives me vast experience towing and hauling with all of the newest trucks on the market today.

"Being based on Detroit," says Rall, "I never miss the North American International Auto Show, the Woodward Dream Cruise and Roadkill Nights, along with spending plenty of time raising hell on Detroit's Woodward Avenue with the best muscle car crowd in the world.

Rall can be contacted at [email protected]

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