AMG is known for building great engines, with a large part of engine production enjoying hand-built status at the Affalterbach facility, located about an hour away from the Mercedes-Benz headquarters in Stuttgart, Germany.
In the past few years Mercedes has re-designed both its V8 and six-cylinder performance engines, and the technology contained within both engines is stunning.
The new 3,0-litre straight-six performance engine
Mercedes-Benz switched from a straight-six engine design to a V6 for its mid-line sedan models about two decades ago. Now it’s switched back to a straight six, and the new engine fitted in the AMG E53 sedan, coupe and cabriolet models is an amazing piece of engineering.
The new six-cylinder features turbocharging, supercharging and a 48-volt electric power boost
The new straight six engine, with the code nameM256, displaces 2 999 cc in AMG E53 form and delivers a very impressive 336 kW and 520 Nm of torque. It achieves this mainly by using a large single turbocharger of twin-scroll design, the reason being that large turbochargers are more efficient at higher revs.
But large turbos suffer from lag compared to smaller ones. They take more time to “spool up” once you push your foot hard on the accelerator, because their internals are heavier.
Enter the supercharger
To help spin up the large turbocharger quickly, Mercedes-AMG employs a small supercharger located downstream of the turbocharger. The supercharger does not use exhaust gas like a turbo, but in this case is driven by a 48-vlt electric motor. Once the turbo is spinning sufficiently, a valve closes and the supercharger is taken “out of play” while the turbo takes over to provide intake charge boost.
And a 48-volt starter-alternator for even more power
At the outset this straight-six petrol engine was designed to incorporate a 48-volt combined starter-alternator system. This device not only starts the car and provides charging for major electric components, but it also provides 16 kW of power to the engine at ultra-low revs. So throttle response is even more instant!
The 48-volt system is also complemented by a separate 12-volt system with its own small battery to operate more traditional 12-volt devices on the car.
The 4.0 litre V8 in the E63 S
There is just one model that uses the 4,0-litre V8 engine in the E-Class range, and that is the E63 S sedan. And the power and performance outputs are impressive: the numbers are 450 kW, 850 Nm of torque, 0-100 km/h in 3,4 seconds and a top speed of 300 km/h.
The lightweight V8 motor was introduced a few years ago and features a pair of twin-scroll turbochargers mounted within the “V” of the engine block, to achieve a more compact design. Many high-performance V8 engine builders follow this layout today, as locating the turbos outside the cylinder V makes for a bulkier engine package. The turbocharging response is also improved with this “in-the-V” layout.
There are various other hi-tech features on this engine, with ducting from alternate cylinders to help minimise turbo lag and minimise emissions. Other features include direct fuel injection and air-water intercooling for the intake charge of air.
Perhaps the most impressive is the V8’s ability to switch to four-cylinder operation by deactivating fuel supply, ignition and closing off the intake and exhaust valves. This occurs on cylinders 2, 3, 5 and 8 under very light or closed-throttle conditions, and the result is impressive fuel saving.
And the efficiency winner?
Impressive though the V8, our efficiency prize goes to the new 3,0-litre straight-six with tis complex turbocharging, electric supercharging and 48 volt mild-hybrid technology.
It has impressive performance with 0-100 km/h in 4,5 seconds and a top speed of 250 km/h. But more importantly its fuel consumption average of 8,7 litres/100 km and 200 g/km of CO2 emissions makes it the winner.
The V8 comes a close second thanks to its huge power output combined with a 10,8 litres/100 km consumption average and 245 g/km of emissions.
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