| Mercedes-Benz M278/M157 | |
| Manufacturer: | Mercedes-Benz Mercedes-AMG (AMG) |
| Production: | 2010–2020 |
| Configuration: | 90° V8 |
| Valvetrain: | DOHC 4 valves x cyl. with VVT |
| Predecessor: | Mercedes-Benz M273 Mercedes-Benz M156 |
| Successor: | Mercedes-Benz M176/M177/M178 |
| Displacement: | 4663cc (M278) 5461cc (M157) |
| Bore: | 92.9mm 98mm |
| Stroke: | 86mm 90.5mm |
| Power: | 300- |
| Torque: | 540- |
| Block: | Aluminium |
| Turbocharger: | Honeywell Bi-turbos |
| Fueltype: | Gasoline |
| Fuelsystem: | Direct injection |
| Coolingsystem: | Water-cooled |
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 from Honeywell, one per cylinder bank, producing 0.9bar boost pressure in most configurations.[2] [3]
Mercedes-Benz estimated that these changes, with vehicle modifications such as a stop-start system, give the 4.7 - litre M278 22% lower fuel consumption and CO2 emissions than the 5.5 - litre M273 while producing more power 3200NaN0 versus 2850NaN0 and torque 7000NaN0 versus 5300NaN0.[2]
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 46631NaN1 with a bore and stroke of NaNmm. Output is 3200NaN0 at 5,250 rpm with 7000NaN0 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 3000NaN0 with 6000NaN0 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 2700NaN0 and 5500NaN0[6]
For 2014 S-Class models (chassis code W222), power is increased to 3350NaN0 at 5,250 rpm, while torque remains at 7000NaN0 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.
Applications:[2]
The second variant, designated M157,[8] is tuned by Mercedes-AMG for use in higher-performance models. This version has a displacement of 54611NaN1 with a bore and stroke of NaNmm.[9] Increased power and torque comes from the increased displacement as well as higher boost pressure of 10NaN0.
There are six states of output with the M157. For the S-Class and CL-Class, power is 4000NaN0 at 5,500 rpm with 8000NaN0 of torque at 2,000-4,500 rpm, or 4200NaN0 at 5,500 rpm with 9000NaN0 of torque at 2,500-3,750 rpm with the optional AMG Performance Package.[9] For the 2013-15 SL-Class, power is 3950NaN0 or 4150NaN0 with the optional AMG Performance Package. For the 2012-2013 E-Class and CLS-Class, power is 3860NaN0 with 7000NaN0 of torque in standard tune, or 4100NaN0 with 8000NaN0 of torque with the AMG Performance Package.[10] Beginning with the 2014 E-Class and CLS-Class, power increases to 4100NaN0 7200NaN0 of torque for standard tune, or 4300NaN0 with 8000NaN0 of torque for "S-Model" variants.[11] [12] At the same time for SL-Class, power increases to 4300NaN0 and 9000NaN0.[13] [14] [15] [16]
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.[17] 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.[18]
Applications:[8]
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.[19]
See main article: Mercedes-Benz M152 engine. 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[20] (up to 30 percent better than the M113 E55 engine used in the previous model). Output is 3100NaN0 at 6,800 rpm, with 5400NaN0 of torque at 4,500 rpm.[21]
Applications
