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  • Writer's pictureMike

Mercedes V8 Sleeper, The M278 Enigne

The Mercedes-Benz M278 is a family of twin-turbocharged V8 engines produced by Mercedes-Benz. Introduced in 2010, the M278 engine replaced the naturally aspirated M273 V8 engines, offering improved fuel efficiency, reduced emissions, and increased performance. Here are the detailed specifications and features of the M278 engine:

Engine Specifications:

  • Configuration: V8

  • Displacement:

  • 4,663 cc (4.7 liters)

  • Bore x Stroke:

  • 92.9 mm x 86.0 mm

  • Compression Ratio:

  • 10.5:1

  • Power Output:

  • Varies by model, typically from 402 hp (300 kW) to 429 hp (320 kW)

  • Torque:

  • Ranges from 600 Nm (443 lb-ft) to 700 Nm (516 lb-ft)

Technical Features:

  • Fuel Injection:

  • Direct fuel injection system (DI) for improved fuel efficiency and performance.

  • Turbocharging:

  • Equipped with twin-turbochargers, one for each bank of cylinders, enhancing power output and efficiency.

  • Intercooler:

  • Air-to-water intercooler system to reduce the temperature of the intake air, improving efficiency and performance.

  • Variable Valve Timing:

  • Continuous camshaft adjustment on intake and exhaust sides for optimized engine performance and efficiency.

  • Start/Stop System:

  • Integrated start/stop system to improve fuel economy by shutting off the engine when the vehicle is stationary.

  • Multispark Ignition:

  • Capable of firing multiple sparks per combustion cycle to ensure complete combustion and reduce emissions.

  • Lightweight Construction:

  • Extensive use of lightweight materials, including aluminum for the engine block and heads, to reduce overall vehicle weight.


The M278 engine is used in various Mercedes-Benz models, including:

  • CL-Class: CL500 (CL550 in the US)

  • S-Class: S500 (S550 in the US)

  • E-Class: E500 (E550 in the US)

  • CLS-Class: CLS500 (CLS550 in the US)

  • SL-Class: SL500 (SL550 in the US)

  • GL-Class: GL500 (GL550 in the US)

  • G-Class: G500 (G550 in the US)

  • ML-Class: ML500 (ML550 in the US)

Performance and Reliability:

The M278 engine is known for its combination of power, efficiency, and refinement. Key aspects include:

  • Fuel Efficiency: Improved fuel consumption compared to its naturally aspirated predecessors, thanks to direct injection, turbocharging, and start/stop technology.

  • Emissions: Reduced CO2 emissions, meeting stringent environmental regulations.

  • Performance: Strong power and torque delivery, providing excellent acceleration and driving dynamics.

Common Issues:

  • Timing Chain Tensioner: Issues with the timing chain tensioner can cause rattling noises and, if not addressed, can lead to more severe engine damage.

  • Oil Leaks: Some engines have experienced oil leaks from various seals and gaskets.

  • Turbocharger Issues: Problems with the turbochargers, including oil leaks or failure, have been reported.

Maintenance Recommendations:

To ensure the longevity and reliability of the M278 engine, regular maintenance is essential:

  • Oil Changes: Regular oil changes with high-quality synthetic oil to maintain engine health.

  • Timing Chain Inspection: Periodic inspection of the timing chain and tensioner to prevent potential issues.

  • Leak Checks: Regular checks for oil leaks and addressing them promptly.

  • Turbocharger Maintenance: Routine servicing of the turbochargers and associated components to ensure proper functioning.

Overall, the Mercedes-Benz M278 engine is a high-performance, efficient, and reliable powerplant, well-suited for a range of luxury and performance vehicles. Regular maintenance and attention to potential issues are crucial for optimal performance and longevity.

Aftermarket Performance:

With the "sleeper" moniker attached to the M278 powered cars the aftermarket is a little thin when compared to its big brother powering the AMG models. That doesnt mean that M278 powered cars dont have a good amount of support. At MBH motorsports we were one of the first to develop M278 downpipes. We started with the CLS550 and quickly moved to the S550, GL550, ML550 and the E550.

When you add downpipes for your M278 powered Mercedes the power gains as a stand alone mod are fairly modest. You can expect to pic up about 20whp without any other supporting mod. This this gain is had by removing the restrictive cats that allow then engine to flow more freely. The reduction of backpressure than can build up in the turbo and engine of your M278 also allows the turbos to have less resistance as they spin all in all this makes the flow of exhaust more efficient. TO the point that if you can keep your foot off the fun pedal you should see an increase in MPG.

When you combine tuning with your M278 downpipes that is when things start to really shine. By adding a tune with your downpipes, the downpipes allow for more timing and ignition to be added to the tuning file. When you combine that with the said benefits of what the M278 downpipes are already doing they power gains can be huge. In some cases reaching AMG M157 power levels.

Not all downpipes are made the same:

First and foremost our downpipes are made in the USA at our Arizona location. We use 16 gauge 304 stainless steel RathGibson tubing. Its pretty much the best of the best. I can just about guarantee all other M278 downpipes are either imported or using inferior quality tubing. In most cases both. As far as we know we are the only downpipes on the market that use RathGibson tubing in all M278 and M157 downpipes. When you see other downpipes from Russia or China sold by others are just about the same price as MBH downpipes, understand with MBH you are getting what we believe is vastly superior materials. Not to mention of world class craftmanship is second to none as well. This is why all of our M278 downpipes come with a lifetime warranty.

Easy Installation:

Our M278 downpipes are a breeze to install across all models. So weather you have a CLS550, E550, S550 or S550 Coupe and so on install should only take about an hour if you have access to a lift. A few tips to installing M278 downpipes or any exhaust for that matter is to loosen your entire exhaust. this allows you some wiggle room to fit the downpipes in. Each section of the downpipes has slip fit joints. these joint are not designed necessarily to be bottomed out . The female side of the slip joint is made a littler deeper than it needs to be, so that you can have some adjustability to get things right where you want them. With all of your downpipes there is no need to drop the engine, remove a motor mount, or any of that stuff. By getting a set of M278 downpipes for your Mercedes You will for sure save yourself some money on install time.

If you are thinking about adding some performance to your M278 equipped Mercedes, starting with a set of downpipes is an absolute must. Here are some popular links for our M278 downpipes

S550 W222

S550 W221

S550 Coupe





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