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New Models
AUTOS: Mercedes Reveals Fuel-Miser V8
New 5.5-liter normally aspirated engine in SLK55 AMG delivers 415 horsepower; cylinder deactivation boosts fuel efficiency 30 percent.
The AMG performance version of the 2012 Mercedes-Benz SLK sports car gets a new V8 with cylinder deactivation for improved fuel economy. (Photo: Mercedes-Benz)
Mercedes-Benz has revealed the full details of a new naturally aspirated 5.5-liter V8 engine with fuel-saving cylinder-deactivation technology for the upcoming 2012 Mercedes-Benz SLK55 AMG.
Even with peak output lifted to 415 horsepower and 398 pound-feet of torque, up from the 355 horsepower and 376 pound-feet of the previous 5.4-liter V8, fuel economy has been improved dramatically, according to the automaker, with four cylinders shut off under partial loads.
The new M152 powerplant, which is based on the existing twin-turbocharged M157 V-8 engine making its way into more of AMG’s top-end models, claims 30 percent better fuel efficiency and is destined to be one of the last high-performance engines in Mercedes’ lineup without the aid of forced induction.
Numerous components and systems between the two engines are identical, such as displacement, bore and stroke, distance between cylinders, the engine stop-start system and direct-injection technology.
Unique to the M152 are its new intake air ducting, new cylinder heads, modified valve drive, custom oil-supply system and optimized crankcase, and the cylinder-deactivation technology.
The engine uses technology developed for Mercedes’ Formula 1 engine, with cylinders two, three, five and eight of the engine cut off under partial load to considerably lower fuel consumption. The cylinder shut-off function is available over a wide engine-speed range from 800 to 3,600 rpm if the driver has selected transmission mode "C" for Controlled Efficiency.
Symbols in the main instrument cluster inform the driver whether cylinder shut-off is active, and whether the engine is currently running in four- or eight-cylinder mode. When running on only four-cylinders, the engine still has a reasonable 170 pound-feet of torque on tap.
Once the driver floors the throttle and the tachometer passes the 3,600 rpm mark, the rest of the cylinders fire up in a process that takes no more than 30 milliseconds, Mercedes says.
The engine is also fitted with a sports exhaust system with integrated flaps, which allows the car to run relatively quiet at low speeds and much louder once the driver dials up the revs. Each of the two rear silencers has a flap which is adjusted depending on the driver's accelerator input and the engine speed.
At low loads and engine speeds below 2,000 rpm, the flaps remain closed. This causes the exhaust gases to cover a longer distance and flow through an additional damping element so that the engine sound is subdued. When the driver accelerates, the flaps open at an angle of 15 degrees, then 30 and up to 50 degrees so that some of the exhaust gases cover a shorter distance. Under full load at higher engine speeds, both flaps are fully opened.
Official EPA figures are yet to be released though we should know more once the engine makes its debut in the 2012 Mercedes-Benz SLK55 AMG at this September’s 2011 Frankfurt Auto Show.
Even with peak output lifted to 415 horsepower and 398 pound-feet of torque, up from the 355 horsepower and 376 pound-feet of the previous 5.4-liter V8, fuel economy has been improved dramatically, according to the automaker, with four cylinders shut off under partial loads.
The new M152 powerplant, which is based on the existing twin-turbocharged M157 V-8 engine making its way into more of AMG’s top-end models, claims 30 percent better fuel efficiency and is destined to be one of the last high-performance engines in Mercedes’ lineup without the aid of forced induction.
Numerous components and systems between the two engines are identical, such as displacement, bore and stroke, distance between cylinders, the engine stop-start system and direct-injection technology.
Unique to the M152 are its new intake air ducting, new cylinder heads, modified valve drive, custom oil-supply system and optimized crankcase, and the cylinder-deactivation technology.
The engine uses technology developed for Mercedes’ Formula 1 engine, with cylinders two, three, five and eight of the engine cut off under partial load to considerably lower fuel consumption. The cylinder shut-off function is available over a wide engine-speed range from 800 to 3,600 rpm if the driver has selected transmission mode "C" for Controlled Efficiency.
Symbols in the main instrument cluster inform the driver whether cylinder shut-off is active, and whether the engine is currently running in four- or eight-cylinder mode. When running on only four-cylinders, the engine still has a reasonable 170 pound-feet of torque on tap.
Once the driver floors the throttle and the tachometer passes the 3,600 rpm mark, the rest of the cylinders fire up in a process that takes no more than 30 milliseconds, Mercedes says.
The engine is also fitted with a sports exhaust system with integrated flaps, which allows the car to run relatively quiet at low speeds and much louder once the driver dials up the revs. Each of the two rear silencers has a flap which is adjusted depending on the driver's accelerator input and the engine speed.
At low loads and engine speeds below 2,000 rpm, the flaps remain closed. This causes the exhaust gases to cover a longer distance and flow through an additional damping element so that the engine sound is subdued. When the driver accelerates, the flaps open at an angle of 15 degrees, then 30 and up to 50 degrees so that some of the exhaust gases cover a shorter distance. Under full load at higher engine speeds, both flaps are fully opened.
Official EPA figures are yet to be released though we should know more once the engine makes its debut in the 2012 Mercedes-Benz SLK55 AMG at this September’s 2011 Frankfurt Auto Show.
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