Mercedes-Benz M278 engine

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Mercedes-Benz M278 / M157
Mercedes-Benz S550 long V222 engine room.jpg
Mercedes-AMG (AMG)
Configuration90° V8
Displacement4.7 L; 284.6 cu in (4,663 cc) (M278)
5.5 L; 333.3 cu in (5,461 cc) (M157)
Cylinder bore92.9 mm (3.66 in)
98 mm (3.86 in)
Piston stroke86 mm (3.39 in)
90.5 mm (3.56 in)
Block materialAluminium
ValvetrainDOHC 4 valves x cyl. with VVT
TurbochargerHoneywell Bi-turbos
Fuel systemDirect injection
Fuel typeGasoline
Cooling systemWater-cooled
Power output300–430 kW (408–585 PS; 402–577 bhp)
Torque output540–900 N⋅m (398–664 lb⋅ft)
PredecessorMercedes-Benz M273
Mercedes-Benz M156
SuccessorMercedes-Benz M176/M177/M178

The Mercedes-Benz M278[1] is a family of direct injected, Bi-turbocharged, V8 gasoline automotive piston engines.

The M278 is derived from the company's previous M273 V8 engine, sharing its bore pitch, aluminium engine block, and Silitec aluminium/silicon low-friction cylinder liners.[2] In contrast to the port-injected M273, the M278 features gasoline direct injection, with piezo-electrically actuated fuel injectors for more precise fuel delivery, and multi-spark ignition, which enables the spark plugs to be fired multiple times over the combustion sequence for more efficient combustion.[2] Other changes relative to the M273 include an increased adjustment range for the variable valve timing system, a new timing chain arrangement, and new engine accessories (such as the oil pump, water pump, fuel pump, and alternator) which reduce parasitic loads. Many of these new features are shared with the M276 V6 engine family, which was announced at the same time.[2]

While the M273 was naturally aspirated, the M278 features twin turbochargers, one per cylinder bank, producing 0.9 bar (13 psi) boost pressure in most configurations.[2]

Mercedes-Benz estimate that these changes, in conjunction with vehicle modifications such as a stop-start system, allow the 4.7–litre M278 to have 22% lower fuel consumption and CO2 emissions than the 5.5–litre M273 while producing more power 320 kW (435 PS; 429 bhp) versus 285 kW (387 PS; 382 bhp) and torque 700 N⋅m (516 lb⋅ft) versus 530 N⋅m (391 lb⋅ft).[2] The M278 is also more refined than its predecessor.[3]

The entire M278 lineup avoids the United States Gas Guzzler Tax, a first for V8 production engines from Mercedes-Benz.[4]


The basic M278 has a displacement of 4,663 cc (4.7 L; 284.6 cu in) with a bore and stroke of 92.9 mm × 86 mm (3.66 in × 3.39 in). Output is 320 kW (429 bhp; 435 PS) at 5,250 rpm with 700 N⋅m (516 lb⋅ft) of torque at 1,800-3,500 rpm for S-Class, CL-Class, SL-Class, and GL-Class models.[2] CLS-Class, E-Class, and M-Class models are detuned to 300 kW (402 bhp; 408 PS) with 600 N⋅m (443 lb⋅ft) of torque at 1,600 rpm.[5] Although it no longer corresponds with the engine displacement, all of the above models are still badged as "550". The GL-Class, besides the GL550 above, also features the GL450 trim that carries a detuned version of the 4.7 L engine making 270 kW (362 bhp; 367 PS) and 550 N⋅m (406 lb⋅ft)[6]

For 2014 S-Class models (chassis code W222), power is increased to 335 kW (449 bhp; 455 PS) at 5,250 rpm, while torque remains at 700 N⋅m (516 lb⋅ft) between 1,800-3,500 rpm. .[7]

These engines are mated to the 7G-Tronic 7-speed automatic transmission, and the new 9G-Tronic 9-speed automatic transmission.



The second variant, designated M157,[8] is tuned by Mercedes-AMG for use in higher-performance models. This version has a displacement of 5,461 cc (5.5 L) with a bore and stroke of 98 mm × 90.5 mm (3.86 in × 3.56 in).[9] Increased power and torque comes from the increased displacement as well as higher boost pressure of 1 bar (15 psi).

There are six states of output with the M157. For the S-Class and CL-Class, power is 400 kW (544 PS; 536 bhp) at 5,500 rpm with 800 N⋅m (590 lb⋅ft) of torque at 2,000-4,500 rpm, or 420 kW (571 PS; 563 bhp) at 5,500 rpm with 900 N⋅m (664 lb⋅ft) of torque at 2,500-3,750 rpm with the optional AMG Performance Package.[9] For the 2013-15 SL-Class, power is 395 kW (537 PS; 530 bhp) or 415 kW (564 PS; 557 bhp) with the optional AMG Performance Package. For the 2012-2013 E-Class and CLS-Class, power is 386 kW (525 PS; 518 bhp) with 700 N⋅m (516 lb⋅ft) of torque in standard tune, or 410 kW (557 PS; 550 bhp) with 800 N⋅m (590 lb⋅ft) of torque with the AMG Performance Package.[10] Beginning with the 2014 E-Class and CLS-Class, power increases to 410 kW (557 PS; 550 bhp) 720 N⋅m (531 lb⋅ft) of torque for standard tune, or 430 kW (585 PS; 577 bhp) with 800 N⋅m (590 lb⋅ft) of torque for "S-Model" variants.[11][12]

These engines are mated to the AMG Speedshift MCT 7-speed semi-automatic transmission, which replaces the 7G-Tronic's torque converter with a wet clutch pack.[13] Note that this MCT 7-speed can handle considerably more torque and is not the same unit as the dual-clutch transmission found on the Mercedes-Benz SLS AMG.[14]


The M157 engine will replace the previous M156 in most of the AMG lineup. Despite the 5.5–litre displacement, all models are designated "63" for marketing purposes.[15]


The third variant, designated M152, is a naturally aspirated derivative of the M157 engine, sharing the same displacement, direct injection, and many other features. The M152 engine includes a cylinder deactivation variable displacement system for improved fuel economy[16] (up to 30 percent better than the M113 E55 engine used in the previous model). Output is 305 kW (415 PS; 409 bhp) at 6,800 rpm, with 540 N⋅m (398 lb⋅ft) of torque at 4,500 rpm.[17]



Honeywell Turbo Technologies produced the turbochargers used in the Mercedes Benz 4.7 L biturbo V8 engines for the S-Class and CL-Class vehicles.[18]


  1. ^ Mercedes' New V Engine Family
  2. ^ a b c d e f g Mercedes-Benz New V6 and V8 Engines are More Powerful and More Efficient
  3. ^ "Archived copy". Archived from the original on 2012-08-18. Retrieved 2012-08-02.CS1 maint: archived copy as title (link)
  4. ^ [1]
  5. ^ 2012 Mercedes-Benz CLS550 - First Drive Review - Auto Reviews - Car and Driver
  6. ^ [2]
  7. ^ 2014 Mercedes S-Class Sets New Standards in Automotive Development
  8. ^ a b 2011 Mercedes-Benz S63 AMG - 2010 Geneva Auto Show Coverage, New Car Reviews, Concept Cars - Automobile Magazine
  9. ^ a b [3]
  10. ^ 2012 Mercedes-Benz CLS-Class In-Depth Overview
  11. ^ [4]
  12. ^ [5]
  13. ^ a b [6]
  14. ^ "Archived copy". Archived from the original on 2010-10-07. Retrieved 2012-01-27.CS1 maint: archived copy as title (link)
  15. ^ [7]
  16. ^ [8]
  17. ^ "Mercedes-Benz details new variable-displacement V8 for SLK55 AMG". Autoblog. 2011-07-21. Retrieved 2011-07-24.
  18. ^ [9]