The V8 is definitely not dead: The power of eight with the efficiency of four

22 Jul

By Matt McCarron

The eight-cylinder engine. Its characteristics has become synonymous with high horsepower, frame-twisting amounts of torque and speed. However, with fuel economy and overall efficiency becoming more important with each passing day, how much longer does the venerable V8 have in a world full of fuel-sipping four-cylinders?

Thankfully all the power-hungry, speed-loving enthusiasts need not be afraid. Yesterday Mercedes AMG announced the creation of an all-new naturally aspirated V8 engine, designated internally as the M152. The new V8 will make its world debut at the Frankfurt International Motor Show in September, and will power the new 2012 SLK55 AMG, the only vehicle in its segment to feature a eight-cylinder engine.

All-new 5.5-liter Mercedes AMG engine

The M152 is the equivalent of Dr. Jekyll and Mr. Hyde with two completely different personalities. The new AMG-derived V8 delivers impressive horsepower and torque figures expected from a hand-built AMG engine, but with a twist. And no, the twist does not refer to the amount of torque inflicted on the frame, rather that the M152 delivers the efficiency of a four-cylinder engine.

One might ask how this combination of power and efficiency is possible. The answer is both simple and highly complex, with technology, and lots of it.

Engineers at Mercedes’ high performance headquarters have incorporated their AMG Cylinder Management cylinder shut-off system into this new V8. The result of this technology is an engine that is capable of producing 415 hp at 6,800 rpm and 398 lb-ft of torque at 4,500 rpm. Not only does this engine produce an additional 60 hp and 22 lb-ft when compare to its predecessor, but it is 30 percent more fuel efficient.

When designing the M152 AMG engineers took ideas and inspiration from the twin turbo 5.5-liter M157 that powers the likes of the CL63 and S63 AMG. The displacement of both engines is identical, along with the ECO stop/start system. However the M152 differs from its forced induction cousin with a different air intake, cylinder heads, modified valve drive, an adapted oil supply system and an optimized crankcase.

The AMG Cylinder Management cylinder shut-off system is a perfect example of just how much technology is going into today’s high-end automobiles in a never-ending attempt to make them more fuel efficient without sacrificing overall performance. To understand how this improved fuel economy is achieve you need to understand how a system like AMG’s cylinder shut-off system works.

When driving in the Controlled Efficiency “C” transmission mode, cylinders two, three, five and eight in the M152 are cut off during partial load. This is available when the engine is operation between 800 and 3,600 rpm. During this range the engine still produces a minimum of 170 lb-ft of torque when running on only four cylinders. If and when the driver feels they need more power and reaches the 3,600 rpm plateau the engine engages the additional four cylinder in less than 30 milliseconds.

The technology placed in the M152 is remarkable, especially when you consider that many of the advanced systems making their way into passenger vehicles were, up until a few years ago, strictly reserved for million dollar race cars. As the auto industry makes its way further into the 21st century it will continue to have to innovate and improve to start ahead of new restrictions and regulations. However, if the M152 proves anything it is that world class performance and fuel efficiency to match can coexist.

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