From its entry-level luxury cars, to exclusive supercars, every Mercedes performs with ease thanks to some of the world’s best engines. We consider how its legendary, since-replaced 6.2L M156 V8 compares to what’s available in M-B’s electrified future, and if a used M156 model is a better option.
Key Points
- The 6.2-liter M156 V8 is the engine that made Mercedes AMG the performance powerhouse it is today.
- Engineers at AMG threw all of the experience gained in 30 years of racing into the M156.
- When the M156 was retired, AMG replaced it with the M177 4.0L twin-turbo V8.
- The M177 engine provides more power and torque, as well as having a better powerband, but it’s lacking in the delivery.
- At some point, AMG will switch to electric powertrains in all its cars, which may make buying an older M-B for the M156 a compelling option.
Mercedes’ Last Big Naturally Aspirated 6.2-liter M156 V8 was Replaced by a Downsized, Turbocharged Engine that may Never Fully Live up to its Predecessor
The entire automotive industry is moving towards an electrified future. Mercedes-Benz has committed to offering at least 10 different all-electric cars by the end 2022. One of the best engines of the last several decades has already been retired.
The 6.2-liter M156 V8 is the engine that made Mercedes AMG the performance powerhouse it is today. It has been replaced by a downsized, turbocharged engine that while good, will never actually replace its predecessor in enthusiasts’ hearts.
It’s worth taking a look at what will surely be Mercedes’ last big naturally aspirated V8 and perhaps even its last great naturally aspirated V8 engine full stop.
Let’s see what made this engine special, take a brief look at its replacement, and then look forward to the future of Mercedes muscle.
AMG began as an engine builder for Mercedes’ racing effort. The move to road cars seemed like a natural extension, but even its most potent engines were still based on engines used in more pedestrian cars. Its first clean-sheet design first appeared in the 2007 Mercedes CLK63 AMG.
All the models this engine appeared in, which is practically all of Mercedes’ entire line, were designated “63” even though the M156 engine is 6,208 cc or 6.2L. Legend has it the 63 is a nod to Mercedes’ first V8, the M100, which was a full 6.3L.
The Mercedes CLK63 AMG engine’s output numbers were equally as impressive, making 475 hp and 465 lb.-ft. of torque.
But, since this was designed to be used across the product line, different power outputs were specified for different models. The most powerful version of the M156 is rated at 518 hp.
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The engineers at AMG threw all of the experience gained in 30 years of racing into the M156. The block and head are constructed of a silicon-aluminum alloy to minimize weight and maximize heat exchange.
Instead of pressing in steel cylinder liners, a new process of plasma coating was used to give the cylinder walls a high hardness, low friction surface.
The M156 engine also uses a forged steel crankshaft, utilizing high-density counterweights inserted into the crank.
Using a heavier material for the counterweights allows them to be smaller, decreasing power loss from the crank splashing through the oil in the crankcase.
At the top end of the engine, the DOHC heads use vertical valves, four per cylinder. The combustion chamber is hemispherical with 40 mm intake valves and 34 mm exhaust valves.
Both intake and exhaust cams use electro-hydraulic adjusters for variable valve timing. Each can adjust up to 40-degrees allowing the engine to use a large amount of valve overlap at low engine loads, improving both emissions and fuel economy.
M177 4.0L Twin Turbo V8 Replaced the M156, Bringing More Power but Less Delivery where it Matters
When the M156 was retired, AMG replaced it with the M177 4.0L twin-turbo V8. The engine provides more power and torque, as well as having a better powerband.
What it’s lacking is in the delivery. Because it uses two very small turbos, they spin up quickly and torque delivery becomes more of an all-or-nothing affair.
The car is somewhat overpowered, to begin with, becomes quite a handful to drive near the limits of its grip, as I found out in my first experience with the car driving it on the Algarve track in Portugal. Every corner exit was a balancing act of keeping the turbos spooled without blasting the rear tires loose with all the torque.
The 6.2L was just as overpowered, but the power was more manageable. The 4.0L delivers more power while being up to 32-percent more fuel-efficient. It’s hard to argue with progress.
We’ll All Miss the Sound of V8s, but Electric Motors Offer Instantaneous Power Delivery and Huge Amounts of Torque
When comparing large displacement engines with their replacement, downsized turbocharged engines, and then their replacements, electric motors, there is a certain amount of irony. Automotive enthusiasts are incapable of lamenting the loss of feel and throttle control that was available with naturally aspirated engines.
But, none of us will deny that having huge amounts of torque from way down in the rev-range all the way to redline is a big upside to forced induction. Electric motors do both of these things inherently well.
Yes, we’ll all miss the sound of V8s, but electric motors can produce maximum torque from zero rpm. Power delivery is instantaneous and infinitely variable.
At some point, AMG will switch to electric powertrains in all its cars. They will drive more like our memories of the old M156-powered cars than the actual cars do.
Mercedes engines have always been among the best in the world. The M156 was the best of the best. It will always occupy a place in the hearts of enthusiasts, even after the days of internal combustion have come to a close.
Photos: Mercedes
