They are distinguished by software only!

They are distinguished by software only!

The Mercedes-Benz M278 – that's the internal designation (where "M" for engine stands /"OM" would stand for oil engine (i.E., diesel) – is a V8 gasoline engine that has been offered in various series since 2010.

Technically closely related to the V6, M 276, which was created in the same development cycle, it also shares with it many advantages and disadvantages.

The M278 is the evolution of its direct predecessor, the M 273. From this took over the basic design, which of course had to be adapted in detail to the increased forces. The market launch of the M 278 took place in CL. S-Class in autumn 2010 instead of. Shortly thereafter, a power-reduced variant (408 hp) debuted in the CLS.

Since then, the engine has been used in the E-Class and CLS, in the S- and CL, SL, and the ML and GL SUVs (more detailed application data below).

II. Technical data

Valves per cylinder

Displacement 4663

Bore 92.9

Stroke 86

Compression ratio

Boost pressure

Fuel compatibility: Up to 25% ethanol, with additional components up to 85% [2]

– Compared with M 273 noticeably higher engine load[3]

Constructive basis M 273, from which essential production-relevant features have been taken over:

– Aluminum crankcase

– Aluminum silicon bushings

– Retention of the compression of the Sauger despite increase of the piston compression height around 4mm by shortening of the connecting rod around 2mm.[4]

– Retention of the basic cylinder head concept from the M 273, but with the addition of a two-part water jacket, for better heat dissipation of the increased combustion chamber load.[5]

Completely new timing chain control drive; Objectives:

– Compact design to reduce the overall height of the engine (crash safety)

– Retention of acoustic qualities and durability

– Improvement of chain friction.[6]

Further development of the wing cell-Camshaft adjuster:

– (weight optimization by 50% / installation space) [7]

– 35% higher actuating speed / 0.4 bar less oil pressure requirement [8]

Exhaust Camshafts[9]:

– Adjustment of the shifting angle on two pairs of exhaust cams for noise comfort under full load and in overrun operation, especially in the low and medium speed range

Predecessor engine was designed for sporty engine sound; now comfort!

Thermal cycle and thermal management[10]:

– Two-disc thermostat with two functions: a) map-controlled regulate different temperatures and b) shut off the water circuit, so that the water in the head and block does not circulate and warms up more quickly during cold starts

– Heating circuit with shut-off valve; water pump power consumption reduced

Oil circuit[11]:

– Map-controlled vane oil pump (aluminum casing) with additional external gear pump as suction stage for ATL

– Engine load and -speed-dependent supply with 2-4 bar via two electrically switched main channel pressure stages[12]

– thereby 35% less drive power compared to conventional fixed displacement pump

Intercooler (air-water) and charge air manifold in the V; all air ducts in stainless steel; thus very good responsiveness[13]

Exhaust gas turbochargers [14]:

– Turbocharger with wastegate that is supplemented by a mechanical vacuum pump to provide vacuum as quickly as possible.

– This makes it possible to dispense with a divert-air valve on the compressor.

Exhaust system:

– Double-walled exhaust pipe from the ATL outlet to the exhaust for the fastest possible response of the catalytic converters [15].

– Waiver of secondary air system [16].

– Soundproofing[17]

– through a crosstalk station (H-pipe in shell construction),

– two seperate middle mufflers (insulation wool + helmet wood resonator),

– Rear silencer (reflection chamber + damping wool).

Exhaust backpressure like the predecessor despite 30% more mass throughput.[18]

Injector and firing method[19]:

– Third generation direct injection

– Operating mode-dependent adjustable common rail pressure 120-180 bar

– New piezo high pressure injector with Multiple Injection (5 very precise injections per cycle)

Waiver of lean shift operation, so that non low sulfur fuel as offered in the main target markets can be used> thereby predominantly on the road with Lambda 1

Start-stop system [20]:

– Intelligent engine shutdown when the engine is at a standstill and the foot brake is depressed

– Direct start when the brakes are released with direct injection on one cylinder and so the engine starts up quickly (350ms)

– For this purpose, the crankshaft sensor provides the necessary data, so that all calculations can take place even when the engine is not running.

– Already after 60° KWU the starter can be switched off.[21]

Shutdown of the engine already after 1.5s idle time advantageous; NEDC savings potential 5%![22]

III. Configuration levels / areas of application

Mechanically, all four variants of the M 278 are completely identical. They are distinguished solely by software!

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