Mercedes M157: Everything You Need To Know

The duumvirate automaker heavyweights prepared their weapon for yet another breakthrough engine that may raise eyebrows for some AMG conservatives since their longing for the Kompressor is insatiable. Well, though it does not have the charisma of those ‘K’ engines, it still fits the shoe of the then-vacated post left by the Kompressors.

This path led to mold the style of Mercedes – luxurious but aggressive.

The success gained from the naturally aspirated M156 engine translated into the same route they followed with the M113 K and into the M157, eventually. They took a page from their previous books and integrated the forced induction into this 5.5 Liter V8.

What are Mercedes M157 Engines?

The Mercedes M157, despite having a larger displacement, only weighs the same as the M156 engine. Its compact profile build and performance-oriented objective wholly utilized the potential in terms of compatibility among a wide variety of AMG-branded vehicles.

Designated as the Mercedes-AMG M157 engine, this 5.5 Liter bi-turbo V8 monster is designed to power AMG-badged vehicle models. The framework of the engine originated from the 4.7 Liter bi-turbo M278 engine. However, the M157 is extensively reworked; it has a higher displacement due to a larger bore and stroke.

It is the second variant of the M278 family released and tuned by the Mercedes-AMG for high-performance usage. These engines are matched with an AMG Speedshift MCT 7-speed semi-automatic transmission, replacing the 7G-Trmoic’s torque converter with a wet clutch pack.

Moreover, this MCT 7-speed is capable of handling more torque and different units as the dual-clutch transmission found in the Mercedes-Benz SLS AMG.

To add, the M157 also features the same cylinder block and heads with the M273, forged steel crankshaft, and connecting rods connected to hyper eutectic-cast aluminum pistons. Early piston rings have a diamond-like coating, a technology adopted from the manufacturer’s racing machines.

Engine Specifications and Design:

  • Production Run: 2010 – 2020
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: biturbo V8
  • Bore: 98 mm
  • Stroke: 90.5 mm
  • Valvetrain: DOHC four valves per cylinder
  • Displacement: 5.5 L (5461 cc)
  • Compression Ratio: 10.0
  • Weight: 450 lbs.
  • Maximum HP: 577 HP at 5,500 RPM
  • Maximum Torque: 590 lb-ft at 2,500 – 3,750 RPM

The Mercedes M157 engine has a lightweight aluminum cylinder block with a 98 mm cylinder bore, 90.5 mm piston stroke and a 10.0 compression rating. The cylinder banks are arranged in a ‘V’ configuration with 106 mm spacing between these cylinders.

Within the bores, the M157 has cast-in Silitec (aluminum-silicon combination) cylinder liners. The Silitec liners undergo a deck plate honing process, which aids the assembled state simulation and static crankcase deformation by mounting a deck stress plate on the cylinder head.

The crankcase ventilation happens through a series of two oil separators, an impactor and a centrifuge. These guys work via a line between the impactor and left air filter.

The ventilation starts at the centrifuge through a pressure regulating valve and a check valve in partial load situations and eventually reaching the partial load branch to charge the air distributor.

The ventilation starts at the centrifuge in full load but goes to the right air filter upstream of the turbocharger via a pressure regulation valve and a check valve. Moreover, full-load vents happen through a line between the oil separator and left air filter to the left filter upstream of the turbocharger.

The M157 engine has a forged steel crankshaft with eight counterweights that rotates on five main bearings. To add, the machine has 146.5 mm fracture-split forged connecting rods and cast aluminum pistons with 30.1 compression height. The M157 AMG first piston ring is coated with diamond-like carbon, a technology applied on most motorsport engines.

The cylinder head is aluminum-made with dual overhead camshafts driven by a two-stage chain drive with three gear chains; each gear chain is tensioned via a hydraulic chain tensioner. The camshafts are made from internal high-pressure formed steel tubes with composite cams.

Furthermore, the heads have a two-piece water jacket and cooling slot between the cylinders. A hydraulic vane-cell camshaft adjuster with a control valve is also installed for a more responsive and instantaneous operation. The adjuster can adjust all camshafts instantly by up to 40 degrees relative to the crankshaft to change valve overlap.

However, the four valves per cylinder are actuated by roller cam followers; the hollow exhaust valves are packed with sodium for dissipating heat.

The M157 AMG has Garrett MGT2260SML turbochargers attached to the two-cylinder banks; these turbos have wastegate control positioned with the cylinder bank. Each of the two exhaust manifolds is fitted with a turbocharger driven by the kinetic and thermal energy of exhaust gases from the connected cylinder bank.

Which, in turn, will carry the air in gap-insulated, welded exhaust manifold and an exhaust downpipe downstream of the turbocharger.

The wastegate is managed via a vacuum from the mechanical vacuum pump placed on top of the engine. With that, the wastegate can be opened in a partial-load situation to reduce fuel consumption and accumulate boost pressure. The wastegate would then be closed by a vacuum from the vacuum unit.

The two-cylinder banks of the engine have a shared water/charge air cooler connected to the low-temperature cooling circuit with a charge air cooler circulation pump and low-temperature cooler. Cooling the charged air increases the density, resulting in more power production, reducing the formation of nitrogen oxides, and reducing the tendency to knock.

The first generation direct fuel injection system is installed in the M157 engine. It has a non-return high-pressure supply with two separate fuel rails. From those rails, the piezo injectors spray refined atomized fuel into the combustion chambers and are capable of providing up to five injections per cycle.

A coupler module is placed inside each fuel injector to ensure that the piezo actuator model and nozzle module have zero clearance in the longitudinal direction. An O-ring seals the fuel feed on the high-pressure side and another to fill the leak line at the fuel injector. Moreover, the seal between the cylinder head and fuel injector is provided by a Teflon ring.

The AMG M157 has an ECO start/stop function. Basically, a start-assisted in-engine direct start function and engine stop function are combined to form a start/stop operation. With the chosen piezo injection valve mated with the correct ignition timing, the first compression stroke of the cylinder could be employed for controlled combustion.

Furthermore, the cylinder with a better piston position will receive the fuel injection into its combustion chamber. This is to allow the engine to set off imminently after starting the machine directly. However, the oil supply to the transmission hydraulics must be maintained while the engine is off and restarted.

The ECO start and stop function adds an additional 12 Ah battery which works as a buffer to cushion voltage drops during engine starts.

And lastly, to reduce energy demand, the M157 AMG has ancillary units.

The power output of the M157 varies depending on the model. The first units fitted to the S-Class and CL-Class produced 536 HP at 5,500 RPM with 590 lb-ft of torque at 2,500 – 3,750 RPM. With an optional AMG performance package, the power production increased to 563 HP at 5,500 RPM with 664 lb-ft of torque at 2,500 – 3750 RPM.

The M157 2013 – 2015 SL-Class power rating is 530 HP and 557 HP with the AMG performance package. For the 2012 – 2013 CLS-Class and E-Class, the output is 518 HP with 516 lb-ft of torque; and 550 HP with 590 lb-ft of torque with the AMG Performance Package.

Starting with the 2014 CLS-Class and E-Class, the power in standard tune would be increased to 550 HP with 531 lb-ft of torque and 577 HP with 590 lb-ft of torque for the “S-model” variants.

It is easy to spot the S-model or Performance Package from the standard versions by simply lifting the hood. AMG dressed these wild M157 with a carbon-fiber engine cover instead of the plastic one.

Applications of the AMG M157 Engine:

  • 2011 – 2017 S 63 AMG
  • 2011 – 2014 CL63 AMG
  • 2012 – 2018 CLS 63 AMG
  • 2012 – 2015 ML 63 AMG
  • 2015- 2019 AMG GLE 63
  • 2012 – 2016 GL 63 AMG
  • 2016 – 2019 AMG GLS 63
  • 2013 – 2018 G 63 AMG
  • 2012 – 2016 E 63 AMG
  • 2012 – 2019 SL 63 AMG

Engine Tuning, Upgrades, and Modifications

Some owners tuned or moded their engines by changing the spark plugs, other aftermarket parts, and ECU.

You can also bring your engine into a shop and undergo a stage 1 intermediate tune to buff the power and torque numbers up. Furthermore, leveling it up to a more powerful machine might be an option after the first. It would be best to consult on specialists if that is possible.

Tuning like this helps you gain an approximate 15-20% increase in both power and torque.

Problems Surrounding the AMG M157 Engine:

Like a high-performance engine, we expect a lot from these machines; some even demand a bulletproof type of engine. However, considering the amount of power it produces, we can say it is pretty reliable as it can withstand those outputs. But, what are external problems we might encounter with M157?

The first one is the timing chain issue. This is most common on early M157 engines, such as the 2011 and 2012 models. These machines have an oil drainage problem coming from the cylinder head on initial start-up leading to oil starvation of the timing chain tensioner. Worst, this causes the timing chain to stretch than usual.

Tune and modded M157 engines frequently suffer misfiring issues on the OEM spark plugs. In addition, a large spark plug gap combined with higher cylinder pressure may result in a blown-out spark plug.

Another issue is coolant hose leaks. As the M157 engine age, its components start to deteriorate, crack, and split; the hose is no exception. These are easy repairs, though, but beware if the leak is bad enough to cause an excessive coolant loss.

That will not end pleasantly as it can lead to overheating, and we all know that overheating is detrimental to the engine. When the engine lacks or is out of coolant, operations will get hot very quickly, affecting the machine’s overall condition.

The Mercedes M157 is also prone to valve timing cover leak, also referred to as the timing case cover. Coolant or oil may leak from a drain hole situated on the front valve timing cover near the thermostat piping. This is generally due to the timing case cover not being mounted properly.

And don’t forget to change your engine oil with the recommended mileage. Change the standard maintenance items such as spark plugs and other components. Use high-quality fuel.

Summary

Overall, this engine is solid and reliable, certainly more reliable than most high-performance engines out there. The M157 definitely met the expectations and overwhelmed some due to its capabilities and potential. Even though it does not have the responsiveness of some AMG, the M157 is a great performer. 

This engine effectively renewed the minds of Mercedes-AMG to provide a more powerful and more efficient V8 without performance trade-offs.

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