Mercedes-Benz has released details of a new engine that will be fitted to the upcoming top performance derivative of the SLK roadster.
Set to be unveiled at the Frankfurt Motor Show during September, AMG confirmed that it wouldn’t be a turbocharged 5,5-litre V8, but a naturally aspirated unit. This also means the new SLK55 AMG will be the only roadster in this segment to still offer a V8 engine.
One of the main reasons manufacturers have been implementing turbocharging in recent years is to be able to offer decent performance with the combination of a lower fuel consumption. With this new M152 5,5-litre V8, Mercedes-Benz decided to implement what it calls AMG Cylinder Management that disables four cylinders under light throttle loads and only activates all eight cylinders once the driver requires more power. The engine will be able to run on four cylinders when the driver has selected the “controlled efficiency” transmission mode. No button needs to be pressed to activate the other four cylinders. If the revs rise above 3 600 r/min, the activation of the other four cylinders is said to be seamless and imperceptible, and takes only taking 30 milliseconds.
With the help of this system, AMG has been able to cut fuel consumption considerably and the claimed usage in the SLK 55 is only 8,5 litres/100 km in the combined cycle.
Delivering 310 kW and 540 N.m, the M152 is based on the M157 5,5-litre V8 biturbo that can be found in the E63 AMG, CL63 AMG (that CAR tested in April 2011) and the S63 AMG. The displacement, bore and stroke, stop/start system and direct petrol injection technology have been carried over. A new intake air ducting, cylinder heads, modified valve drive, adapted oil supply and an optimised crankcase is some of the features that are unique to the M152.
Mercedes-Benz also confirmed that the engine’s red line will be 7 200 r/min. It seems some of the magical characteristics that we have got used to in the legendary 6,2-litre V8 have been carried over and engineered into this M152.
Specification: AMG M152 5.5-litre V8 engine
Displacement: 5 461 cm3
Bore x stroke: 98,0 x 90,5 mm
Compression ratio: 12,6 to 1
Power output: 310 kW @ 6 800 r/min
Torque output: 540 Nm @ 4 500 r/min
Dry engine weight: 187 kg
CAR will be attending and reporting directly from the Frankfurt Motor Show during September.
