Mercedes-Benz A-Class Engine

High tech from four cylinders

• AMG 2.0-litre four-cylinder turbo engine with 265 kW
• The world’s most powerful four-cylinder engine in series production
• Exciting power delivery, high pulling power
• Fuel consumption of 6.9 litres per 100 kilometres (NEDC combined)
• Compliance with EU6 emissions standards right from the market launch
• Mercedes-Benz A-Class

When designing and developing the powerful AMG 2.0-litre four-cylinder turbo engine, the Mercedes-AMG experts drew inspiration from a wide variety of sources – including the technology of the AMG 5.5-litre V8 biturbo engine (M 157) and the AMG 6.0-litre V12 biturbo engine (M 279). AMG’s four-cylinder in-line turbo engine – in-house designation M 133 – also incorporates several decades of motorsport experience.

With an output of 265 kW and a peak torque of 450 Newton metres, the high-performance unit belonging to the BlueDIRECT engine family is the world’s most powerful four-cylinder engine in series production. The AMG turbo engine also stands out from the crowd when it comes to power density: a figure of 133 kW per litre puts the four-cylinder in-line unit on par with the world’s most powerful super sports cars. With a maximum charge pressure of 1.8 bar, the AMG 2.0-litre four-cylinder turbo engine leads the field in this respect, too. The M 133 likewise sets new standards in terms of efficiency and environmental compatibility: the A 45 AMG boasts an NEDC combined fuel consumption of 6.9 litres per 100 kilometres – making it the most fuel-efficient high-performance car in the Mercedes‑AMG model range. The A 45 AMG already meets the requirements of the EU6 emissions standards.

Driving performance, excitement, emotive appeal

The characteristics of the AMG 2.0-litre four-cylinder turbo engine add up to driving enjoyment. Be it on account of their responsiveness, pulling power or engine sound – the A 45 AMG delivers excitement right from the very first mile. One of the defining aspects of the driving sensation is the rich torque: a constant 450 Newton metres is on tap between 2250 and 5000 r/min. The spontaneous response to accelerator pedal movements and the lightening fast run-up to the governed maximum speed of 6700 r/min leave a lasting impression. Much of the emotive appeal is down to the engine sound – not least when combined with the optional AMG performance exhaust system with exhaust flap.

The key data at a glance:

*Electronically limited

The exciting engine characteristics and impressive technical data are largely down to the high-tech package put together by Mercedes-AMG. The M 133 – a high-performance unit belonging to the Mercedes-Benz BlueDIRECT engine family – displays many of the technical features of the AMG 5.5-litre V8 biturbo engine (M 157): the spray-guided direct petrol injection system includes the piezo injectors positioned centrally in the four combustion chambers and multiple injection with an injection pressure of 200 bar. In combination with the multiple spark ignition, it allows higher thermodynamic efficiency, which in turn leads to better fuel utilisation and a sustainable reduction in particulate emissions. The A 45 AMG already complies with the second stage of the EU6 emissions legislation that does not go into effect until 2017. The injection system’s outstanding flexibility also ensures a high level of degrees of freedom for the application. There are up to five injections per combustion cycle in the cold-start and warm-up phase that is so crucial in terms of emissions. Here one of the key aspects for particulate reduction is the reduction of the partial injection quantities. The four-valve-per-cylinder design with continuously variable camshaft adjustment, alternator management and the ECO start/stop function are likewise familiar features from the eight-cylinder biturbo engine (M 157).

Twin-scroll turbocharger for spontaneous response

The spontaneous reactions to accelerator pedal movements and the excellent throttle response are down to a fast build-up of charge pressure and torque. The engineers addresses the challenges concerning the response of small-displacement turbo engines by combining a twin-scroll turbocharger with maximum derestriction of the exhaust system and multiple injection. Unlike conventional systems, a twin-scroll turbocharger merges the exhaust gas ducts of cylinder pairs in the flow-optimised manifold. The advantages of the special twin-scroll manifold: exhaust gas back pressure, exhaust gas temperature and exhaust gas impulse ensure an optimum gas exchange. By the same token, the engine’s tendency to knock and the residual gas in the cylinders are minimised.

Twin-scroll technology not only enhances key engine characteristics – it also helps to reduce fuel consumption and exhaust emissions. The optimised intake manifold with extremely short air paths and, an exceptionally compact compressor housing, additionally ensure spontaneous response and fast reactions to accelerator pedal movements. The wastegate valve integrated in the twin-scroll exhaust gas turbocharger is vacuum-controlled by an electropneumatic converter, allowing a reduction in exhaust gas back pressure and dethrottling under partial loads, which in turn lowers fuel consumption.

Pure high tech inside the engine, too

The inner workings of the engine are just as sophisticated and high tech as the turbocharger: one typical feature of powerful racing engines is the weight-optimised crank assembly with forged steel crankshaft and forged pistons with friction-optimised piston rings. These components were developed for motorsport and are also used in the SLS AMG super sports car; they reduce the oscillating masses and ensure exceptionally fast rev up. Pressure-controlled oil-spray nozzles in the crankcase ensure efficient cooling of the highly stressed piston crowns.

Another innovation transferred from the SLS AMG is NANOSLIDE technology – a process which tribologically optimises the surfaces of the piston walls. A considerably harder surface is achieved compared to conventionally coated cylinder walls. The advantages are low friction and wear accompanied by outstanding durability.

A technology known as “spectacle honing” comes from the AMG 5.5-litre V8 naturally aspirated engine (M 152) in the SLK 55 AMG: in this process, the cylinder liners receive their mechanical surface treatment when already bolted in place. As honing would no longer be possible with the cylinder head installed, a jig resembling spectacles is bolted to the crankcase. The cylinder liners distort as if the cylinder head were in place, and are only then given their mechanical surface treatment. As a result, any static distortion of the cylinder liners caused by tightening the cylinder head bolts can be completely eliminated. The positive effects of this process are: reduced friction losses, low oil consumption and lower fuel consumption.

Engine cooling with high-tech components

High power output and maximum stability – the cooling system in the A 45 AMG has to meet strict requirements. The principle of effective air-to-water intercooling is the same as that seen in the AMG 5.5-litre V8 biturbo engine and AMG 6.0-litre V12 biturbo engine. A cooler extending across the complete front level of the cooling module and situated behind the radiator grille is supplemented by an additional cooler in the right wheel arch. The principle: together with the intercooler, which is connected in series, a high-performance electric pump ensures the required flow through the water coolers located behind the large intake ports. This provides for ideal cooling of the highly compressed charge air, thereby contributing towards optimum engine performance. The transmission oil cooling is integrated into the water cooling circuit for the engine. The radiator positioned behind the front fascia is supported by the heat exchanger which is fitted directly on the transmission and supplied with cooling water as required by means of an auxiliary pump.

To ensure optimum stability, the twin-scroll turbocharger has a sophisticated engine-off cooling system: a separate water pump allows the coolant to continue circulating, thus preventing temperature peaks when the hot engine is switched off. Extreme loads of the kind that occur when driving on the racetrack do therefore not have a negative impact on service life.

For spontaneous deceleration and response, AMG’s four-cylinder turbo engine has electronically controlled fuel delivery with fully variable fuel pressure that can be controlled on demand between 100 and 200 bar. The fuel intake in the 56-litre tank has been optimised in line with the high performance of the A 45 AMG: the pump integrated in the tank ensures reliable delivery even at high lateral acceleration levels.

Further highlights of the AMG 2.0-litre four-cylinder turbo engine:

• Gravity-die sandcast all-aluminium crankcase with ventilation bore (optimises comfort and efficiency)
  • Variable camshaft adjustment (optimises output, fuel consumption and exhaust gas emissions)
  • Low-resistance air filter (optimises output)
  • Controlled oil pump (optimises fuel consumption)
  • Two-mass flywheel with centrifugal pendulum (optimises comfort)
  • Viscous vibration damper on belt drive (optimises comfort)

AMG sports exhaust system with automatic exhaust flap

The twin-pipe AMG sports exhaust system is equipped with an automatically controlled exhaust flap. This technology, based on the same principle as that used in the SLK 55 AMG, enables the engine sound to be changed depending on the driving situation: subtle and restrained when cruising or throaty and distinctive when accelerating and driving dynamically – acoustically, this technology perfectly reconciles the two apparently conflicting aims of tangible dynamic spirit and hallmark Mercedes comfort on long journeys. The exhaust flap is continuously adjusted by the engine control unit according to the power called up by the driver, load status and engine speed. As a powerful compact car, the A 45 AMG has a sportier and much throatier sound than its competitors.

An AMG Performance exhaust system with exhaust flap is available as an optional extra. This system gives the driver an even more emotive, fuller engine sound when driving under full load and when changing gears. The double-declutching function during downshifting and the interruption of ignition and injection during upshifting under full load produce a particularly throaty sound with the AMG Performance exhaust system and create a level of emotionality which is otherwise the preserve of engines with more than four cylinders.

Sophisticated emission control system to ensure compliance with the
EU6 emissions standards

Both exhaust systems have a ceramic catalytic converter mounted near the engine firewall, which ensures fast response and, therefore, low untreated emissions. In addition, the exhaust pipe between the turbocharger and the catalytic converter has special insulation and also helps to accelerate heating of the ceramic catalytic converter. The A 45 AMG already meets the requirements of the EU6 emissions standards, which do not go into effect until 2015. It also undercuts the particle concentration limit of 6 × 10¹¹ particles/km that will be compulsory starting in 2017. The large exhaust pipe cross sections – diameter of 80 millimetres upstream and 75 millimetres downstream of the catalytic converter – minimise the exhaust gas back pressure and optimise both power and torque output.

Engine production – a tradition of hand-built excellence

“One man, one engine” – the traditional AMG philosophy also applies to the AMG 2.0-litre four-cylinder turbo engine. Like all AMG eight- and twelve-cylinder engines, the new turbo engine is assembled entirely by hand.

An exclusive assembly line has been set up for the new AMG engine at the Mercedes-Benz engine production plant in Kölleda – where all four-cylinder engines are built for the A-, CLA- and B-Class models. A characteristic feature of the “one man, one engine” production process is the AMG engine badge bearing the signature of the responsible engine fitter. Apart from serving as an AMG hallmark confirming superlative production quality, the AMG engine badge also attests to the peerless DNA of Mercedes-Benz’s high-performance brand.