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New Mercedes AMG V-8 Delivering Near-I-4 Mileage

Green performance without the hybrid?

by on Jul.21, 2011

Mercedes's AMG division claims the new M152 engine going into the SLK55 AMG will deliver big gains in power - and a 30% bump in fuel economy.

With the upcoming launch of its latest powertrain, AMG, the Mercedes-Benz performance division, claims it will be able to deliver the muscle of a traditional AMG V-8 with the mileage of a compact 4-cylinder powertrain.

While that might be a mild exaggeration, the claims are nonetheless impressive if the new 5.5-liter V-8 – developed specifically by AMG – actually can yield a 30% improvement in fuel economy compared to the brand-within-a-brand’s current 5.5-liter V-8.

Until recently, fuel economy was way down the list of attributes Mercedes officials were likely to emphasize – especially at AMG – but studies show that even the affluent buyers who ante up for cars like the Mercedes-Benz SLS AMG supercar now list mileage as a concern.

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The new powertrain will find its first application on the AMG-upgraded version of Mercedes’ compact roadster, the new 2012 Mercedes-Benz SLK 55 AMG.  Significantly, the 30% mileage improvement comes despite a 60 horsepower bump, to 415 hp, with torque jumping from 376 to 398 lb-ft on the new model.

Dubbed the M152, the new engine starts out with the fundamental architecture of the older M157 AMG V-8, a bi-turbo package that debuted only a year ago on the CL63 AMG and S63 AMG models.  But it opts for natural aspiration, among other things, and incorporates a new cylinder deactivation feature that shuts off half of its eight cylinders when power demands are light.

The ECO stop/start system is maintained – shutting off the engine when the vehicle is idled at a light or in traffic then automatically restarting it when the driver’s foot lifts off the brake.  Other changes include new intake air ducting, new cylinder heads, the modified valve drive, an adapted oil supply system and an optimized crankcase.

“The M152 sets an outstanding example for efficiency, while demonstrating the creativity and expertise of our engineers, who took their inspiration from Formula 1 when developing the cylinder shut-off system,” said Ola Källenius, Chairman of Mercedes-AMG GmbH.

The SLK55 AMG is set for a formal introduction at the upcoming Frankfurt Motor Show.  The maker likely won’t release specific mileage numbers until then and EPA validation won’t be completed until close to launch, so it remains to be seen if U.S. motorists really will get the promised improvement over the 2011 model.

The current SLK 55 AMG is rated at 14 mpg City, 22 Highway, with a combined 18 mpg average.  If the new, naturally aspirated V8 meets expectations, it would bump the combined rating to somewhere around 23 to 24 mpg.  And with the added power the roadster might do considerably better than the current 4.9 second 0 to 60 times.

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