Mercedes-Benz M139 engine

The M139 is a turbocharged inline-four engine produced by Mercedes-Benz. It is the successor of the M133 engine. It is also the first four-cylinder engine by AMG to be specified with two outputs, to be assembled by hand using "one man, one engine" philosophy, and to be equipped with combined port and direct fuel injection system. At 310 kW on its introduction, M139 was the world's most powerful four-cylinder engine in serial production with specific output of 208 hp per litre or 104 hp per cylinder. The current top trim of the M139 produces 350 kW, giving it a specific output of 175 kW per litre or 87.5 kW per cylinder, making it the current most powerful four-cylinder engine in serial production.

Design
The M139 engine is based on the current M260 engine, which is an upgraded version of the outgoing M270, sharing the same bore and stroke dimension as well as the block. Unlike the normal M260, the AMG engineers rotated the engine block 180 degrees so that the intake system is in the front of the engine, while the turbochargers and exhaust headers are situated between the engine and firewall. The rotation optimises the engine air flow for higher performance and with shorter distance and fewer diversions. This also "allows the flattest possible and aerodynamically advantageous front section design." The exhaust valves in M139 engine are bigger than ones in M133 engines for higher flow. The compression ratio is raised to 9.0:1 for M139 from 8.6:1 for M133. The two-stage fuel injection system, a first in AMG four-cylinder engine, has the piezo injectors delivering the fuel directly into the combustion chambers as first stage and solenoid valves in the manifolds as second stage for increased specific output.

An electrically assisted turbocharger system by Garrett Motion is used.

Performance
The M139 engine has two specific outputs: 285 kW and 480 Nm for the base version; and 310 kW and 500 Nm for the S-model.

M139 (285 kW version)

 * 2019 - Mercedes-AMG CLA 45 4MATIC+ (C118)
 * 2019 - Mercedes-AMG A 45 4MATIC+ (W177)
 * 2020 - Mercedes-AMG GLA 45 4MATIC+ (H247)
 * 2022 - Mercedes-AMG SL 43 (R232)
 * 2022 - Lotus Emira (268 kW / 360 hp)

M139 (300 kW version)

 * 2022 - Mercedes-AMG C 43 4MATIC+ (W206)
 * 2024 - Mercedes-AMG GLC 43 4MATIC+ (X254)

M139 (310 kW version)

 * 2019 - Mercedes-AMG CLA 45 S 4MATIC+ (C118)
 * 2019 - Mercedes-AMG A 45 S 4MATIC+ (W177)
 * 2020 - Mercedes-AMG GLA 45 S 4MATIC+ (H247)
 * 2024 - Mercedes-AMG GT 43 (C192)

M139I (350 kW version)

 * 2022 - Mercedes-AMG C 63 S E Performance 4MATIC+ (W206)
 * 2024 - Mercedes-AMG GLC 63 S E Performance 4MATIC+ (X254)