The Mercedes-BenzM278 is a family of direct injected, Twin-turbocharged, V8gasolineautomotivepiston engines. The M278 is derived from the company's previous M273V8 engine, sharing its bore pitch, aluminium engine block, and Silitec aluminium/silicon low-friction cylinder liners. 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. 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 which reduce parasitic loads. Many of these new features are shared with the M276 V6 engine family, which was announced at the same time. While the M273 was naturally aspirated, the M278 features twin turbochargers, one per cylinder bank, producing boost pressure in most configurations. Mercedes-Benz estimate that these changes, in conjunction with vehicle modifications such as a stop-start system, allow the 4.6-litre M278 to have 22% lower fuel consumption and CO2 emissions than the 5.5-litre M273 while producing more power versus and torque versus. The M278 is also more refined than its predecessor. The entire M278 lineup avoids the United StatesGas Guzzler Tax, a first for V8 production engines from Mercedes-Benz.
M278 (base)
The basic M278 has a displacement of with a bore and stroke of. Output is at 5,250 rpm with of torque at 1,800-3,500 rpm for S-Class, CL-Class, SL-Class, and GL-Class models. CLS-Class, E-Class, and M-Class models are detuned to with of torque at 1,600 rpm. 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 4.6 L engine making and For 2014 S-Class models, power is increased to at 5,250 rpm, while torque remains at between 1,800-3,500 rpm.. These engines are mated to the 7G-Tronic 7-speed automatic transmission, and the new 9G-Tronic 9-speed automatic transmission. Applications:
The second variant, designated M157, is tuned by Mercedes-AMG for use in higher-performance models. This version has a displacement of with a bore and stroke of. Increased power and torque comes from the increased displacement as well as higher boost pressure of. There are six states of output with the M157. For the S-Class and CL-Class, power is at 5,500 rpm with of torque at 2,000-4,500 rpm, or at 5,500 rpm with of torque at 2,500-3,750 rpm with the optional AMG Performance Package. For the 2013-15 SL-Class, power is or with the optional AMG Performance Package. For the 2012-2013 E-Class and CLS-Class, power is with of torque in standard tune, or with of torque with the AMG Performance Package. Beginning with the 2014 E-Class and CLS-Class, power increases to of torque for standard tune, or with of torque for "S-Model" variants. These engines are mated to the AMG Speedshift MCT 7-speedsemi-automatic transmission, which replaces the 7G-Tronic's torque converter with a wet clutch pack. 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. Applications:
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.
M152
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 deactivationvariable displacement system for improved fuel economy. Output is at 6,800 rpm, with of torque at 4,500 rpm. Applications
