2012 Mercedes-Benz CLS63 AMG Engine In-Depth
The Mercedes-Benz CLS 63 AMG is setting standards, as evidenced by its fuel consumption of 2.6 gallons per 62 miles
by John Clark | 16 January 2011
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A new AMG high-performance engine is expected to deliver maximum performance in all areas – and the AMG 5.5-litre V8 biturbo engine driving the new CLS 63 AMG is no exception to this rule. Whether its maximum performance, torque and power delivery, engine sound, suitability for long journeys or renowned Mercedes reliability, the powerful 410 kW (557 hp) eight-cylinder engine is able to meet all of the demands which are made of it. Future challenges also include being able to achieve optimum values when it comes to efficiency too, however. Here again the CLS 63 AMG is setting standards, as evidenced by its fuel consumption of 9.9 litres (2.6 gallons) per 100 kilometres (62 miles) (NEDC combined).
As such the performance Coupé demonstrates how exciting dynamism and low fuel consumption can be combined to impressive effect. 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 stop/start function.
Mercedes-AMG is systematically following the trend towards increasing efficiency with its V8 biturbo engine: with a displacement of 5461 cubic centimetres 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. It develops a peak output of 386 kW (525 hp) and maximum torque of 700 Nm. In conjunction with the AMG Performance Package these figures increase to 410 kW (557 hp) and 800 Nm.
Despite an increase in output of 8 kW (11 hp) and 32 kW (43 hp) respectively, and in torque of 70 and 170 Nm compared to the naturally aspirated V8, which develops 378 kW (514 hp) and 630 Nm, AMG engineers have been able to reduce fuel consumption and CO2 emissions considerably. With an NEDC fuel consumption of only 9.9 litres per 100 kilometres, the new CLS 63 AMG betters its predecessor by 4.6 litres. This equates to a fuel saving of more than 32 percent, which engine specialists consider to be nothing less than a quantum leap. CO2 emissions have likewise been significantly reduced: at 231 grams per kilometre, the figure is almost 32 percent lower than for the previous model (345 g/km). Both engine variants achieve identical consumption and emissions values. Thanks to the increased efficiency, it has been possible to reduce the volume of the fuel tank from its previous 80 litres to 66 litres. An 80-litre tank is also optionally available at no extra cost.
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 CLS 63 AMG accelerates from zero to 100 km/h in 4.4 seconds, and with the AMG Performance package the Coupé reaches the 100 km/h mark in 4.3 seconds. The top speed of both engine variants is 250 km/h (electronically limited).
Key data at a glance:
|CLS 63 AMG||CLS 63 AMG with AMG Performance package|
|Valves per cylinder||4||4|
|Displacement||5461 cc||5461 cc|
|Bore x stroke||98.0 x 90.5 mm||98.0 x 90.5 mm|
|Cylinder spacing||106 mm||106 mm|
|Output||386 kW (525 hp) at 6800 rpm||410 kW (557 hp) at 5750 rpm|
|Output per litre||71 kW (96 hp)||75 kW (102 hp)|
|Max. torque||700 Nm at 1750 – 5000 rpm||800 Nm at 2000 – 4500 rpm|
|Torque per litre||128 Nm||146 Nm|
|Maximum engine speed||6400 rpm||6400 rpm|
|Mean pressure||18.5 bar||20.8 bar|
|Engine weight (dry)||204 kg||204 kg|
|Power/weight ratio||0.39 kg/hp||0.36 kg/hp|
|Fuel consumption NEDC combined||9.9 l/100 km||9.9 l/100 km|
|CO2 emissions||231 g/km||231 g/km|
|Acceleration 0 – 100 km/h||4.4 s||4.3 s|
|Top speed||250 km/h*||250 km/h*|
* electronically limited.
Combination of twin turbocharging and direct petrol injection
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 particularly fine distribution of the fuel droplets into the air in the combustion chamber. The result is 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 on a fully variable and demand-related basis.
Two exhaust gas turbochargers and efficient air/water intercooling
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 into the combustion chambers per hour. The maximum charge pressure is 1.0 bar, and 1.3 bar 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 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 low-temperature 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 millimetres and are designed for particularly low pressure loss.
Aluminium crankcase with Silitec cylinder liners
The crankcase of the AMG 5.5-litre V8 biturbo engine is of diecast aluminium. The low (dry) engine weight of just 204 kilograms is the result of uncom-promising lightweight construction methods, and leads to the car’s very balanced weight distribution. The bearing cover for the main crankshaft bearings is of grey cast iron, and 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 crankcase cavities arranged in series. Normally the upward and downward movement of the pistons causes air to be forced into and extracted from the sump, which leads to increased internal friction losses and therefore a reduction in output. The ventilation holes prevent this by ensuring effective pressure compensation between the cavities.
The forged crankshaft of high-grade 38MnS6BY steel alloy 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 four per cylinder. The exhaust valves, which are subject to high thermal loads, are hollow and sodium-filled. Four overhead camshafts operate the 32 valves via low-maintenance, low-friction cam followers. The infinitely 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 variable 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 terms of noise comfort compared with cylinder roller chains.
Efficient 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 two and four 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 particularly clever solution: after a cold start, initially the engine oil is only cooled via the oil/water heat exchanger. 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. 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. A selectable water thermostat ensures rapid warming of the coolant when starting the engine and driving off.
The engine coolant is cooled using the particularly effective crossflow principle. There is a transverse flow of coolant through both the crankcase and the cylinder heads. Additional cooling slots in the cylinder head ensure 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.
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 all of the vehicle’s 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 – an ignition amplifier – at each cylinder. These ensure 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.
Exhaust system with new catalytic converter housings
Low exhaust emissions, compliance with country-specific standards, a characteristic AMG engine sound and a weight-optimized design – the requirements for the exhaust system of the new AMG 5.5-litre V8 biturbo engine were manifold and complex. The CLS 63 AMG complies with all the current EU-5 emission standards, as well as meeting all 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 1.0 millimetre in thickness ensure 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 emissions 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.
The on-demand lambda control guarantees optimum composition of the fuel/air mixture in all operating conditions, to avoid damaging the catalytic converters. This also benefits the fuel consumption under full load, as the mixture can be leaner than in engines without this control system.
Lightweight AMG sports exhaust system for a characteristic sound signature
The twin-pipe AMG sports exhaust system has a pipe cross-section of 70 milli-metres from the manifolds to the rear silencers. Thanks to a particularly intelligent lightweight design, it has been possible to save 4.3 kg of weight compared with the previous model. The AMG experts achieved this by reducing the wall thickness of all of the exhaust pipes as well as the centre and rear silencers to 1.2 millimetres.
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 accelerating and double-declutching, but unobtrusiveness at constant speeds. Unpleasant frequencies or droning noises were effectively eliminated during a series of painstaking tests. The sports exhaust system emits a sonorous eight-cylinder sound that is typical of AMG, while the striking chrome twin tailpipes feature a new design.
Engine production – tradition of hand-built excellence
Like all other AMG engines, the new eight-cylinder biturbo is assembled by hand in the AMG engine shop taken into commission in 2002. Highly-qualified technicians assemble the M157 according to the “one man, one engine” philosophy, maintaining the very strictest quality standards. This painstaking care is attested to by the signature on the characteristic AMG engine plate.
Long tradition of powerful AMG V8 engines
Powerful eight-cylinder engines are an inseparable part of AMG’s corporate history. Established in 1967, the company immediately caused a stir with the 300 SEL 6.8 AMG which succeeded in taking second place at the 24-hour races at Spa-Francorchamps (Belgium) in 1971. The AMG racing saloon was technically based on the Mercedes-Benz 300 SEL 6.3. With an engine output of 184 kW (250 hp) at 4000 rpm and a top speed of 220 km/h, this luxury V8 saloon was Germany’s fastest regular production car at the time. Classic tuning as well as an enlarged displacement from 6330 to 6835 cc resulted in an increase in output to 315 kW (428 hp) at 5500 rpm and in torque from 500 to 608 Nm.
A further milestone in the AMG engine story was the M117, the first eight-cylinder unit with four-valve technology. With a displacement of 5.6 litres, 265 kW (360 hp) and 510 Nm of torque, this V8 accelerated the Mercedes-Benz 300 CE 5.6 AMG to a top speed of 303 km/h in 1987. This made the coupé the fastest German car in series production, and American fans reverently christened it “The Hammer”.
Another important engine in the history of AMG was the supercharged AMG 5.5‑litre V8 introduced in 2001: the M113 K developed an output of up to 428 kW (582 hp) and torque of 800 Nm. The supercharged AMG 5.5-litre V8 in the SLR McLaren of 2003 was even more powerful – the M155 developed up to 478 kW (650 hp) and 820 Nm. 2005 saw the debut of the AMG 6.3-litre V8 engine; depending on the model, the naturally aspirated, high-revving M156 developed up to 386 kW (525 hp) and 630 Nm. Exclusively reserved for the SLS AMG, the likewise 6.3-litre M159 has a maximum output of 420 kW (571 hp) and maximum torque of 650 Nm.
Numerous victories in the “International Engine of the Year Awards”
The supercharged AMG 5.5-litre V8, the AMG 6.3-litre V8 and the AMG 6.0-litre V12 biturbo were all able to win the Best Performance Engine category in the International Engine of the Year Awards. The AMG 6.3-litre V8 also won in 2009 and 2010 in the “Above 4 litres” class.