Emotional peak performance and enormous torque, agile power delivery and a characteristic engine sound, comfort on long journeys and hallmark Mercedes reliability: expectations are high when Mercedes-AMG introduces a new high-performance engine – and its very first biturbo eight-cylinder is no exception. Two criteria are inexorably gaining in importance, namely efficiency and economy. Mercedes-AMG is confronting the challenges of the future, and demonstrating that dynamic performance can be perfectly combined with fuel economy.
The new AMG 5.5-litre biturbo engine combines performance with efficiency to apreviously unknown extent. This is made possible by a unique combination of innovative high-tech systems such as direct petrol injection, twin turbochargers, air/water intercooling and the Controlled Efficiency start/stop function. The eight-cylinder biturbo engine celebrated its market debut in the S 63 AMG in September 2010.
Mercedes-AMG is systematically following the trend towards increasing efficiency with its new V8 biturbo engine: with a displacement of 5461 cc it is precisely 747 cc below the 6208 cc of the naturally aspirated AMG 6.3-litre V8. Nonetheless it considerably betters it in terms of output and torque.
The AMG 5.5-litre V8 biturbo engine develops a peak output of 400 kW (544 hp) and maximum torque of 800 Nm (590 lb-ft). In conjunction with the AMG Performance Package these figures increase to 420 kW (571 hp) and 900 Nm (664 lb-ft). The torque curve in particular shows that no other engine in this output class is able to match the figures delivered by the new Mercedes-AMG biturbo unit.
Despite an increase in output by 14 kW (19 hp) resp. 34 kW (46 hp) and in torque by 170 and 270 Nm (125 and 199 lb-ft) compared to the naturally aspirated V8, which develops 386 kW (525 hp) and 630 Nm (465 lb-ft), AMG engineers have been able to reduce fuel consumption and CO2 emissions considerably.
With a provisional NEDC fuel consumption of only 10.5 l/100 km (22.40 mpg/US, 9.52 km/l), the new S 63 AMG betters its predecessor by 3.9 litres. This equates to a fuel saving of more than 25 percent, which engine specialists consider to be nothing less than a quantum leap. CO2emissions have likewise been significantly reduced: at 246 grams per km, the figure is 28.5 percent lower than for the previous model (344 g/km).
The achievement of these efficiency and environmental aims has no negative effects whatsoever on dynamic performance. On the contrary, as the new AMG 5.5-litre V8 biturbo fully lives up to AMG’s brand commitment to “performance:” the S 63 AMG accelerates from zero to 100 km/h (62 mph) in 4.5 seconds, and has a top speed of 250 km/h /155 mph (electronically limited). With the AMG Performance package, the high-performance saloon reaches the 100 km/h (62 mph) mark in 4.4 seconds and reaches a top speed of 300 km/h /186 mph (electronically limited).
Mercedes-AMG is presenting an attractive high-tech package with its combination of biturbo charging and direct petrol injection with spray-guided combustion. The innovative injection technology brings decisive advantages with respect to fuel consumption and exhaust emissions, thanks to higher thermodynamic efficiency. Particularly fast and precise piezo-electric injectors spray the fuel into the combustion chambers, ensuring a homogenous fuel/air mixture and highly effective combustion.
An electric low-pressure pump delivers the fuel from the tank to a high-pressure pump in the boot with a pressure of six bar. The fuel pressure in the high pressure rail is controlled between 100 and 200 bar (1450 and 2900 psi) on a fully variable and demand-related basis.
Two turbochargers and efficient air/water intercooling
Two turbochargers located next to the cylinder banks supply the eight cylinders with fresh air. At their maximum speed of 185,000 rpm under full load, the two turbochargers force 1750 kg (3858 lbs) of air into the combustion chambers per hour. The maximum charge pressure is 1.0 bar (14.5 psi), and 1.3 bar (19 psi) with the AMG Performance package. Thanks to their specific, compact construction – the turbine housings are welded to the exhaust manifold – there are significant space advantages and the catalytic converters also heat up more rapidly.
The new AMG V8 is the first turbocharged engine to dispense with the usual blow-off valve. This neat solution enabled the compressor housing to be made extremely compact. To ensure agile responsiveness with no time lag, all the air ducts in the intake tract are as short as possible. The wastegate valve, which reduces the pressure in the exhaust system during negative load changes, is vacuum-controlled via an electropneumatic converter. This allows dethrottling under partial loads, which in turn lowers the fuel consumption.
As was already the case in the AMG 6.0-litre V12 biturbo engine, the new eight cylinder direct-injection unit uses particularly efficient air/water intercooling. The low-temperature cooler with its water circulation is space-savingly accommodated within the V of the cylinder banks. It effectively cools down the intake air compressed by the turbochargers before it enters the combustion chambers, and maintains a constantly low intake temperature under full load. A large radiator at the car’s front end ensures defined cooling of the water circulating in the lowtemperature circuit. This guarantees a high output and torque yield in all ambient temperatures and operating conditions. Extremely short charge air ducting makes for outstanding responsiveness. The stainless steel pressure pipes for the fresh and charge air are produced by the hydroforming process, have a wall thickness of only 0.8 mm and are designed for particularly low pressure loss.