Engine and power transmission: Dynamism, performance and efficiency

May 8, 2012
  • AMG 5.5-litre V8 biturbo engine producing up to 415 kW (564 hp)
  • Impressive engine sound, pulling power and power delivery
  • NEDC combined fuel consumption of 9.9 litres per 100 km
  • ECO start/stop function fitted as standard
  • AMG SPEEDSHIFT MCT 7-speed sports transmission
Performance and fuel consumption, power delivery and exhaust emissions, engine sound and characteristic Mercedes reliability – the AMG 5.5-litre V8 biturbo engine in the new SL 63 AMG meets the widest variety of requirements in all areas. This is made possible thanks to a combination of innovative high-tech systems such as direct petrol injection, twin turbochargers with air/water intercooling and the ECO start/stop function.
The eight-cylinder engine develops maximum power of 395 kW (537 hp) and maximum torque of 800 Nm. For the first time the Performance package is also available for the SL 63 AMG, which increases the values to 415 kW (564 hp) and 900 Nm. As a result the new AMG Roadster offers more power than any of its competitors in this segment. The variant with the AMG Performance package also boasts increased charge pressure which has been pushed from 1.0 to 1.3 bar, and a high-quality real carbon-fibre engine cover, among other features.
A glimpse at the performance underlines the exceptional drive dynamics: the SL 63 AMG accelerates from zero to 100 km/h in 4.3 seconds - with the AMG Performance package this figure drops to 4.2 seconds - while the top speed is 250 and 300 km/h (electronically limited) respectively. A determining factor for the power delivery is the broad torque curve: a constant 800 Nm of torque are available between 2000 and 4500 rpm. With the AMG Performance package, as much as 900 Nm can be called upon between 2250 and 3750 rpm. The impressive characteristics of the eight-cylinder biturbo engine make it suitable for all driving styles: whether completing high-speed laps on a closed-off racing circuit, driving extended stretches on the motorway or enjoying cruising along picturesque country roads with the vario-roof open – the AMG 5.5-litre V8 biturbo engine is the very model of effortless superiority and emotional appeal. The characteristic AMG eight-cylinder sound emanating from the two chromed twin tailpipes of the weight-optimised AMG sports exhaust system also has enormous potential to excite.
Enhanced performance and torque, reduced consumption
While output and torque have been increased compared with the previous AMG 6.3-litre V8 naturally aspirated engine (386 kW and 630 Nm), fuel consumption has been significantly reduced: the SL 63 AMG consumes 9.9 litres per 100 km (NEDC combined, 231 g CO2/km) and as such ranks at the top of its segment. The reduction of 4.2 litres compared with the predecessor equates to a decrease of 30 percent. Both power variants have identical consumption figures.
The key data at a glance:
Cylinder arrangement
Cylinder angle
Valves per cylinder
5461 cc
Bore x stroke
98.0 × 90.5 mm
Cylinder spacing
106 mm
Compression ratio
395 kW (537 hp) at 5500 rpm
415 kW (564 hp) at 5500 rpm*
Output per litre
72 kW (98 hp)
76 kW (103 hp)*
Max. torque
800 Nm at 2000-4500 rpm
900 Nm at 2250-3750 rpm*
Torque per litre
146 Nm 165 Nm*
Maximum engine speed
6400 rpm
Engine weight (dry)
204 kg
Power/weight ratio
0.38 kg/hp 0.36 kg/hp*
Fuel consumption, NEDC combined
9.9 l/100 km
CO2 emissions
231 g/km
Acceleration 0-100 km/h
4.3 s
4.2 s*
Top speed
250 km/h**
* with AMG Performance package ** electronically limited
A paragon of efficiency: the AMG 5.5-litre V8 biturbo engine
The key to this performance is the AMG 5.5-litre V8 biturbo engine, designated as the M 157, which premiered in 2010 in the S 63 AMG and CL 63 AMG. It has also been the dynamic driving force behind the E 63 AMG and CLS 63 AMG. The M 157 is a paragon of efficiency and boasts a wealth of technological highlights. On account of higher thermodynamic efficiency, the combination of twin turbochargers, direct petrol injection and spray-guided combustion allows better fuel economy and results in lower exhaust emissions. An electric low-pressure pump sends the fuel from the tank to a high-pressure pump in the engine compartment at a pressure of 6 bar. The pressure of the fuel in the high-pressure rail is fully variable on demand between 100 and 200 bar, ensuring agile response in any driving situation.
Further highlights of the innovative and unique eight-cylinder powerplant from Affalterbach include an all-aluminium crankcase, four valves per cylinder with camshaft adjustment, air/water intercooling, alternator management and the standard-fit ECO start/stop function. Whereas the previous AMG 6.3-litre V8 naturally aspirated engine had a displacement of 6208 cc, the new AMG
5.5-litre V8 biturbo engine needs just 5461 cc.
Two exhaust gas 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 of air per hour into the combustion chambers. The maximum charge pressure is 1.0 bar, or 1.3 bar if the AMG Performance package is included. Thanks to their special, compact design – the turbine housings are welded to the exhaust manifold – there are significant space advantages, and the catalytic converters also heat up more rapidly.
The AMG V8 dispenses with the usual blow-off valve. This neat solution has 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 AMG experts have enabled the wastegate valve, which reduces the pressure in the exhaust system during negative load changes, to be 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 in the SL 65 AMG, the eight-cylinder direct-injection unit uses particularly efficient air/water intercooling. The low-temperature cooler with its water circulation is accommodated within the V of the cylinder banks to save space. It effectively cools down the intake air compressed by the turbochargers before it enters the combustion chambers, and maintains a constantly lower intake temperature under full load. The large radiator at the car's front end ensures defined cooling of the water circulating in the low-temperature circuit. Extremely short charge-air ducting makes for optimum 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 millimetres and are designed for very low pressure loss.
All-aluminium crankcase with Silitec cylinder liners
The crankcase for the AMG 5.5-litre V8 biturbo engine is made of diecast aluminium. The low (dry) engine weight of 204 kilograms is the result of uncompromising lightweight construction methods and gives the vehicle balanced weight distribution. The bearing cover for the main crankshaft bearings, made of grey cast iron, is bolted to the crankcase for high rigidity. Cast-in Silitec cylinder liners ensure that the eight pistons operate with low friction.
Drilled ventilation holes in the crankcase lead to a higher output and fuel savings under partial load: above the bearing blocks there are longitudinally drilled holes which connect the adjacent crankcase cavities. Normally the upward and downward movement of the pistons causes air to be forced into and extracted from the sump, which leads to increased resistance and therefore a reduction in output. The ventilation holes prevent this by ensuring effective pressure compensation between the cavities.
The forged crankshaft made of high-grade 38MnS6BY steel alloy (a combination of the chemical elements manganese, sulphur, boron and yttrium) rotates in five main bearings, has eight counterweights and has been optimised with respect to torsional rigidity, inertia, low rotating masses and a long operating life. A two-mass viscous damper mounted at the front reliably eliminates vibrations. Each connecting rod journal on the crankshaft carries two forged, cracked connecting rods. In the interests of low mechanical friction and high wear resistance, the lightweight pistons have a metallic contact surface. Pressure-controlled oil-spray nozzles in the crankcase ensure that the highly stressed piston crowns are efficiently cooled.
Four-valve technology with variable camshaft adjustment
Perfect charging of the combustion chambers is ensured by large intake and exhaust valves, of which there are two per cylinder. The exhaust valves, which are subject to high thermal loads, are hollow in order to reduce weight and also sodium-cooled. Four overhead camshafts operate the 32 valves via low-maintenance, low-friction cam followers. The continuously variable camshaft adjustment within a range of 40 degrees on the intake and exhaust sides depends on the engine load and engine speed, leading to outstanding output and torque values. This also results in consistent idling at a low speed.
Depending on the engine speed, valve overlap can be varied for the best possible fuel/air supply to the combustion chambers and efficient removal of the exhaust gases. The camshaft adjustment is carried out electromagnetically via four pivoting actuators, and is controlled by the engine control unit. The camshafts are driven by three high-performance silent chains, which have considerable advantages in noise comfort compared to cylinder roller chains.
Innovative oil supply and water cooling
Efficient oil delivery under all load and operating conditions is ensured by an oil pump with an electrically controlled compression stage. The oil pressure can be varied between 2 and 4 bar, which has advantages in terms of friction and fuel consumption. An extraction stage integrated into the oil pump for the two turbochargers prevents oil from being entrained into the charge air and exhaust gases, thereby helping to reduce emissions even further. Both the sump and the extraction point have been optimised for maximum lateral acceleration and efficient lubrication. The oil capacity is 10.5 litres.
The combined water/oil cooling system is a clever solution: after a cold start, initially the engine oil is fed through the oil/water heat exchanger. The advantage of this system is that the engine oil warms up more rapidly, as the engine coolant warms up faster and the oil is later cooled by the coolant. If the cooling performance of the very compact cooler is insufficient, the flow is additionally directed through the external engine oil/air cooler by an oil thermostat. A selectable water thermostat ensures rapid warming of the coolant when starting the engine and driving off.
The engine coolant is cooled using the efficient crossflow principle. There is a transverse flow of coolant through both the crankcase and the cylinder heads. Additional cooling slots in the cylinder head allow more efficient cooling of the combustion chambers, which has advantages during combustion: it enables earlier ignition timings to be chosen without incurring the risk of knocking. Large openings in the AMG front apron help to ensure effective airflow over the water, engine oil, charge air and transmission oil coolers.
Alternator management and optimised belt drive
A significant contribution to the low fuel consumption comes courtesy of the optimised belt drive, the on-demand control of all ancillary units and pumps, and the alternator management: whenever the V8 engine is on the overrun or when braking, kinetic energy is used to charge the battery rather than being wasted as heat in the usual way. In all other operating modes a combination of electrical-system and alternator management enables the alternator to be kept at a low voltage. This reduces the load on the engine and makes for fuel savings of around 0.15 litres per 100 kilometres according to the NEDC standard, and up to 0.2 litres per 100 km in city traffic with its frequent overrun and braking phases.
Highly efficient engine electronics for every function
All the engine functions are executed and controlled by a particularly efficient Bosch MED 17.7.3. control unit. This state-of-the-art engine computer not only controls the direct petrol injection, charge pressure, camshaft adjustment and variable oil supply, but also communicates with other onboard control units, such as those of the AMG SPEEDSHIFT MCT 7-speed sports transmission. The microprocessor has more than 30,000 different parameters and functions stored in its memory, and is able to perform up to 260 million individual operations per second. To reduce the load on the engine control unit, the eight individual ignition coils have an integral electronic module on each cylinder. This ensures a strong ignition spark at all engine speeds and under all load conditions. The highly precise fuel distribution of the piezo-electric injectors is handled by eight high-voltage output stages.
New catalytic converter housings for low exhaust emissions
Low exhaust emissions, compliance with country-specific standards, a characteristic AMG engine sound and a weight-optimised design – the requirements for the exhaust system of the AMG 5.5-litre V8 biturbo engine were manifold and complex. The SL 63 AMG complies with the EU5 emission standards, and also meets the requirements of the US market (LEV-II standard, On-Board Diagnosis II and lambda sensor diagnosis).
The turbochargers are welded to the exhaust manifolds, while air gap-insulated manifolds with an inner shell measuring only 1.2 millimetres in thickness allow a rapid catalytic converter response. For efficiency and to save space, this concept has a tandem catalytic converter housing on each side of the vehicle: adjacent to the firewall, two thin-walled ceramic substrates are grouped into each housing. This solution makes the previous, additional underbody catalytic converters unnecessary. The two ceramic substrates differ to ensure rapid and efficient emission control: the front one is coated with palladium, while the rear one has a bimetal coating of palladium and rhodium. One lambda sensor per row of cylinders is located in front of each catalytic converter housing, and there is a lambda diagnostic sensor between each of the two thin-walled substrates.
AMG sports exhaust system for a characteristic sound signature
The twin-pipe AMG sports exhaust system has a pipe cross-section of 70 millimetres from the manifolds to the rear silencers. Thanks to a particularly intelligent lightweight design, it has been possible to save 12.3 kg of weight compared with the previous model. The AMG experts achieved this with a whole series of measures:
  • reduction of the wall thickness of all of the exhaust pipes
  •  joint housing for underfloor and firewall catalytic converters
  • redesigned switchover valve
  • centre muffler featuring pipe design for reduced volume
  • new tailpipe trim integrated into the bumper
  • optimised suspension elements
When designing the sound, the aim was to create a perfect synthesis of perceived dynamism and the comfort on long journeys that is the hallmark of a Mercedes. The goal of the developers was to achieve an emotional experience when starting the engine, accelerating and double-declutching, but unobtrusiveness at constant speeds. Unpleasant frequencies or droning noises were eliminated during a series of tests. The sports exhaust system emits a sonorous eight-cylinder sound that is typical of AMG from the new chromed twin tailpipes integrated into the bumper.
Engine production – a tradition of hand-built excellence
Like all other AMG engines, the eight-cylinder biturbo is assembled by hand in the modern AMG engine shop. Highly-qualified technicians assemble the M 157 according to the "one man, one engine" philosophy, maintaining the very strictest quality standards. This painstaking care is attested to by the responsible engineer's signature on the characteristic AMG engine plate.
Power transmission: maximum driving pleasure, reduced consumption
RACE START, double-declutching function, seven gears, four transmission modes and ECO start/stop function: the power transmission of the SL 63 AMG combines extreme emotional appeal, maximum driving pleasure and optimum economy. The AMG SPEEDSHIFT MCT 7-speed sports transmission excites with a combination of unique options.
The AMG SPEEDSHIFT MCT 7-speed sports transmission is exclusive to Mercedes-AMG and combines the sporty, direct and agile responsiveness of a manual transmission with the high levels of comfort of an automatic transmission. MCT stands for Multi-Clutch Technology and indicates that only clutch elements are employed to perform gearshifts. A compact wet start-up clutch, which runs in an oil bath, replaces the conventional torque converter. Thanks to its low rotational inertia, the transmission responds instantaneously and dynamically without the losses typical of a torque converter transmission – thereby helping to save fuel. The AMG sports transmission also impresses with its low weight of just 80 kilograms, which has been made possible through the use of lightweight magnesium for the transmission housing. Vibrations are effectively eliminated by a two-stage torsion damper, with resulting benefits in perceived passenger comfort.
ECO start/stop function fitted as standard
The ECO start/stop function fitted as standard is permanently active in the consumption-optimised "Controlled Efficiency" ("C") driving mode. Once the driver comes to a halt e.g. at a red traffic light or in a traffic jam, the engine is automatically switched off. Once the brake pedal is released or the accelerator is depressed, the engine is immediately restarted and the car is able to move off quickly. Intelligent technology guarantees a comfortable and immediate starting procedure: a crankshaft sensor which recognises the direction of rotation registers the resting position of all eight pistons. For an automatic engine start, the cylinder with the most favourable piston position receives an injection of fuel into its combustion chamber.
The engine management ensures that the engine is only switched off if certain preconditions are met. The starter battery must have sufficient charge, for example, and the engine must be at the necessary operating temperature for efficient emissions control. The same applies to the interior temperature selected by the driver: if this has not yet been reached, the engine is not switched off when the car comes to a stop. The onboard network management system makes sure that active audio, telephone or video functions are not interrupted by the ECO start/stop function.
A green "ECO" symbol shows the driver when the ECO start/stop function is active. Should one of the above criteria be preventing activation of the system, this is shown in the central display by the message "Start/stop inactive" and a yellow "ECO" symbol. In the more performance-oriented driving modes "S" (Sport), "S+" (Sport plus) and "M" (Manual), the ECO start/stop function is always deactivated.
Consumption-optimised Controlled Efficiency ("C") drive mode
When adapting the MCT sports transmission to the AMG 5.5-litre V8 biturbo engine, the AMG engineers paid special attention to the new driving mode Controlled Efficiency ("C"). The emphasis was on delivering minimum engine speed in the highest possible gears in all driving situations. When moving off in "C", the transmission always selects second gear and shifts decidedly early to the next higher gears if the driving style permits. At 60 km/h for instance, sixth gear will already be engaged – not only improving fuel consumption but also noise levels. Thanks to its powerful, readily available torque even at low engine speeds, the AMG V8 biturbo unit is absolutely ideal for this style of driving. Controlled Efficiency also means convenient gearshifts and a "soft" accelerator response set-up for outstandingly smooth power transfer. The use of a new low-friction oil as well as the implementation of further detailed measures in the AMG
SPEEDSHIFT MCT 7-speed sports transmission enhance the efficiency and ensure an additional reduction in consumption.
Drive modes "S", "S+" and "M" for even more driving pleasure and dynamism
In addition to Controlled Efficiency ("C"), three transmission modes are available to meet the demands of drivers looking for a more dynamic ride: in "S" (Sport) mode, the engine and transmission take on a much more agile character. Accelerator pedal movements trigger a more direct traction response, making the downshifts more spontaneous. The engine speed is allowed to reach a higher level in each gear, while the gearshifts in "S" are around 25 percent faster than in "C". Turning the rotary switch in the AMG DRIVE UNIT a notch further to the right activates "S+" mode. "Sport plus" shifts the gears another 25 percent faster than in "S". The same applies to the manual shift mode "M". In "S+" and "M" modes, gearshifts at full throttle take just 100 milliseconds.
The engine management system partially suppresses cylinders in "S", "S+" and "M" modes: precisely interrupting ignition and injection under full load for brief periods leads to even faster gearshifts than before. The highly emotional vocals are an appealing side effect of this lightning-fast process.
Ultra-fast, spontaneous multiple downshifts are another forte of the AMG SPEEDSHIFT MCT 7-speed sports transmission. For instance, kickdown allows gearshifts straight from seventh down to fourth gear, or from fifth to second. In the "S", "S+" and "M" driving modes the automatic double-declutching function is active. Every manual or automatic downshift is accompanied by precisely metered double-declutching – with increasing intensity from "S" through "S+" to "M". And this not only adds to the driver's emotional experience: the load-free downshift minimises load-change reactions, which pays particular dividends when braking into bends – and also enhances safety in the wet
or on ice.
No automatic downshifts in manual "M" mode
In manual “M” mode the driver also benefits from the high torque of the V8 biturbo engine, as there is no automatic downshift under full load and kickdown; the transmission remains steadfastly in the selected gear. Moreover, the MCT sports transmission does not perform an automatic upshift in manual mode when the rev limit is reached. In “M” mode the AMG instrument cluster displays the current gear and alerts the driver visually to the need for an upshift just before the needle reaches the red zone. This means that a particularly sporty driver can use the superior performance potential to its fullest extent. When approaching the lower rev limit, e.g. when braking the vehicle, there is an automatic downshift to the next lower gear.
The powerful electronic transmission control unit with integrated 80 MHz processor controls spontaneous downshifts – say when the driver suddenly needs power for dynamic acceleration.
The AMG DRIVE UNIT is the central control unit for the AMG SPEEDSHIFT MCT 7-speed sports transmission and all driving dynamics functions. The electronic rotary switch to select the four drive modes, including activation of the Race Start function, is located behind the E-SELECT selector lever. Next to this are three buttons for additional functions: the first controls the 3-stage ESP®, the second the AMG sports suspension. The third adorned with AMG lettering is used to store the personal set-up. Briefly pressing the AMG button brings up the configuration options, whilst holding down the button allows you to program the required set-ups - this is confirmed by an acoustic signal. The current settings may be viewed in the instrument cluster by pressing the button at any time.
The Race Start function delivers maximum dynamism: while the vehicle is at a standstill, the driver can activate the ESP® sports function and press the brake pedal with their left foot. Having preselected the Race Start program using the rotary switch, a confirmation message comes up on the AMG central display. The driver then simply needs to confirm the Race Start function by pulling the "Up" shift paddle once, fully depressing the accelerator and taking their foot off the brake. The optimum start-up engine speed is set fully automatically and the SL 63 AMG accelerates away with flawless traction – all the way up to top speed, if so required. It is not necessary to shift up through the gears manually; the AMG transmission changes gear with lightning-fast shift times.