M139: everything you need to know about this Mercedes engine
The M139 engine is a defining milestone in the evolution of AMG engines, setting a new benchmark for performance and innovation. Dubbed the world's most powerful four cylinder engine in series production, this 2.0 liter powerhouse delivers unmatched engine output, thrilling performance, and engineering precision. Developed by AMG engineers, the M139 is the successor to the M133 and serves as a core piece in Mercedes AMG’s compact high-performance lineup.
For tuning professionals and aftermarket specialists, understanding the nuances of the M139 is essential. At bFlash, we support these professionals with industry-leading ECU read/write tools and unique unlocking services that give access to the full potential of this impressive platform.
M139 Development and History
The M139 engine was introduced in 2019, following years of engineering refinements by AMG engineers who aimed to break all limitations previously associated with four cylinder engines. With roots in the proven M133, the M139 was built from the ground up using driverless transport systems, series production lines, and one engine, one technician philosophy in AMG’s Affalterbach facility. Notably, it features closed deck construction, which ensures optimum heat dissipation and structural rigidity for high-pressure performance.
Compared to its predecessor, the M139 produces around 40 hp more and features a host of design changes including a reversed layout, positioning the turbocharger and exhaust manifold at the rear of the engine for better exhaust flow and improved fresh air intake. This configuration enhances both packaging and thermodynamic efficiency.
Technical Specifications of M139
The M139 is a 2.0 liter, inline-4 turbo engine that pushes boundaries with up to 416 hp and 369 lb ft of torque in the "S" model. Even the base version produces an impressive 380 hp 354 lb ft, placing it among the most powerful four cylinder engines in the world. Its specific output of over 200 hp per liter is made possible by an arsenal of engineering enhancements:
M139 Engine Layout and Design
Closed deck construction ensures durability at high cylinder pressures.
Cylinder head is made from high-strength aluminum alloy with optimum heat dissipation characteristics.
Overhead camshafts are driven via low-friction timing systems.
A larger oil sump and refined air deflector design help improve cooling.
Unique layout places twin scroll turbocharger at the rear, reducing exhaust flow distance and improving boost response.
Performance Metrics
0-100 km/h in under 4 seconds (depending on vehicle setup)
Engine speed capability of up to 7,200 rpm
Compression ratio: 9.0:1 for the "S" model
Torque curve optimized for lower engine speeds, ensuring a broad powerband
Improved power delivery and responsiveness from low rpm to redline
Unique Features and Innovations of M139
AMG engineers have taken a holistic approach to improving power delivery, responsiveness, and efficiency.
Twin scroll turbocharger with turbine housing and first stage/second stage pressure regulation enhances exhaust flow and reduces lag.
Direct fuel injection with multiple injection nozzles and solenoid valves ensures more precise control of combustion.
Advanced roller bearings reduce mechanical friction within the turbo.
Forged aluminum pistons and forged steel crankshaft for reduced weight and improved durability.
Exhaust manifold integrated into the cylinder head to optimize fresh air and exhaust exchange.
Heat exchanger and engine’s coolant circuit actively manage thermal loads.
Minimal friction strategies throughout the block and camshaft systems.
Further optimization comes from injection nozzles that deliver fuel with pinpoint accuracy to the combustion chambers, resulting in a cleaner and more efficient burn. The engine also incorporates aerodynamically advantageous airflow solutions, ensuring fewer obstacles in the path of fresh air and fuel injection.
Applications
The M139 is primarily found in high-performance Mercedes AMG compact cars such as:
Mercedes-AMG A45 / A45 S
Mercedes-AMG CLA45 / CLA45 S
Mercedes-AMG GLA45 / GLA45 S
Select AMG performance platforms in development.
Its integration into various chassis highlights its adaptability, whether in front-biased AWD systems or more rear-oriented setups for dynamic handling. The consistent delivery of full engine output across all platforms, regardless of model or drivetrain configuration, demonstrates the engine’s versatility and advanced engineering.
Environmental Impact and Efficiency
Despite its formidable engine output, the M139 was designed with sustainability in mind:
Lightweight materials such as molten aluminum in the engine block help reduce weight.
Optimized combustion chambers and fuel injection strategy increase thermal efficiency.
Focused efforts on reducing mechanical friction and low friction coatings.
Aerodynamically beneficial air deflector designs minimize drag in the engine bay.
The M139 also utilizes advanced cooling technologies, including heat exchangers and controlled engine coolant circuits, to reduce thermal strain and increase efficiency under high-load conditions. As a result, fuel economy figures remain competitive even with such a high specific output.
Maintenance and Reliability
The M139’s series production benefits from meticulous quality control and high-end materials:
Forged aluminum pistons and a forged steel crankshaft contribute to long-term durability.
Enhanced transmission oil cooling and engine’s coolant circuit protect key components.
Fewer diversions in the air intake system lead to consistent performance.
Design prioritizes reduce friction and minimal wear, even under heavy load.
The use of closed deck construction and low friction internals results in an engine that is not only robust but also highly tunable. Even with aftermarket enhancements, wear and tear remain predictable and manageable when proper maintenance routines are followed.
For professionals, regular diagnostic checks using tools like bFlash ensure that systems related to fuel injection, boost control, and engine speed parameters are operating within safe limits. This ensures that tuning does not compromise longevity.
How to flash M139 with bFlash
At bFlash.eu, we are proud to offer the only tool on the market that supports unlocking and flashing of the M139 ECU. When you unlock your mercedes with us you can :
Write to the ECU calibration
Compatibility with various AMG models equipped with the M139 engine
Seamless integration into your tuning workflow, with full support from our engineering team
Our unique Mercedes unlock service is essential for tuning professionals. After sending in the ECU, we unlock the control module, giving you access to:
Full map access for ignition, fuel, torque, turbo boost, and more
Ability to adapt software to new hardware or custom requirements (Some tuners increase power up to 520+ hp with a bigger turbocharger and basic engine modifications on the four cylinder)
Restore to stock or load optimized calibrations
With bFlash, you can take advantage of the M139’s:
Full control over turbo boost levels and specific output in power
Ability to modify torque curves for better drivability
Fine-tuning of fuel injection and exhaust flow
Exhaust valves and calibration allow sound tuning for advanced tuners
This process allows tuning professionals to unleash full engine output while maintaining the mechanical integrity of the amg four cylinder engine.
We offer user-friendly software, robust hardware, and responsive support to help you maximize the power and efficiency of every M139 engine you work on.
At bFlash, we are also able to Unlock other MDG1 platforms from Mercedes. One you have a bFlash, it is possible to Unlock and flash OM654, OM656 and M256 engines.
Conclusion
The Mercedes AMG M139 engine isn’t just a technological marvel, it’s a statement by Mercedes AMG that four cylinder engines can deliver supercar-worthy performance when engineered with passion and precision. With cutting-edge features such as a forged internals, direct injection, and minimal friction design principles, the M139 sets a new benchmark for what compact performance engines can achieve. The four cylinder engine has beaten the specific output records with the S model and its 416 hp. With one engine, Mercedes AMG was able to offer a four cylinder engine block that defies what we thought possible in a mass produced engine with a reasonable compression ratio.
Thanks to bFlash, tuning professionals can now harness the full potential of this powerful four cylinder unit with a seamless ECU unlocking and flashing solution, redefining what's possible in the tuning aftermarket. Whether you're aiming for better drivability, more torque at low rpm, or higher engine speed performance, the M139 paired with bFlash puts all the right tools at your fingertips.
In the world of performance tuning, precision and control are everything. With access to components like the exhaust valves, intake system, and transmission oil parameters, you can unlock performance safely. Use bFlash to minimize risk, maximize gains, and offer your clients world-class tuning services with the full power of AMG engineering behind you.