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New Mercedes Four-Cylinder Engine Generation Four newly developed petrol engines developing up to 141 kW/192 bhp are to be introduced from mid-2002. Fuel consumption is reduced by more than 19 % thanks to direct injection, while torque increases by 15 % and emissions are comfortably below the EU-4 limits.
Installed in the C-Class and Other Models The engines, which will initially be installed in the C-Class and subsequently in other Mercedes model series, highlight the shape of things to come in all the major areas of development: fuel consumption, torque characteristics, power delivery, lightweight design and refinement. The 1.8-litre engine is available in four guises, all featuring the unique Twinpulse system, which combines a compressor supercharger, intercooler, four valves per cylinder, variable valve timing, Lanchester balancer and an adaptive drive system.
The newly developed four-cylinder engines will initially be installed in the C-Class and subsequently in other MercedesBenz model series.
The new four-cylinder engines have power outputs ranging from 105 kW/143 bhp to 141 kW/192 bhp. From the end of 2002, Mercedes-Benz will also offer a direct-injection petrol engine developing 125 kW/170 bhp for the first time. This is the first engine of its kind to combine direct-injection technology with a compressor supercharger and counter-balancer. The new engine develops more power, yet it consumes over 19 % less fuel than the equivalent C-Class predecessor model. Fuel consumption in the C 200 CGI is a mere 7.8 litres per 100 kilometres (sulphur-free Super Plus, NEDC combined consumption).
Over 75 % of the torque is available from just 1500 rpm, and the direct-injection engine develops its maximum torque of 250 Nm from 3000 rpm. It maintains this impressive torque up to 4500 rpm.
Enhanced Dynamism and Lower Fuel Consumption The new C 180 Kompressor accelerates from 0 to 100 km/h in 9.7 seconds, going on to reach a top speed of 222 km/h. Fuel consumption has been reduced by a full litre to 8.4 litres per 100 kilometres (NEDC combined consumption), a saving of more than
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10 %. The maximum torque of 220 Nm is some 15 % higher than in the predecessor model (190 Nm) and available from just 2500 rpm. Meanwhile, the new C 200 Kompressor consumes over 11 % less fuel than its predecessor. Its four-cylinder engine develops a maximum torque of 240 Nm at 3000 rpm (predecessor model: 230 Nm). In terms of power output and torque, the C 230 Kompressor (141 kW/192 bhp, 260 Nm) is the star of the four-cylinder engine line-up. This version, which Mercedes-Benz will install in the C-Class Sports Coupé, delivers a fuel saving of 0.7 litres per 100 kilometres compared to its predecessor.
High Thermal Efficiency The engineers have ensured that the new engines deliver exemplary fuel consumption, primarily by shifting the operating points to engine speed ranges that offer optimum thermodynamic efficiency. In addition, reducing the displacement to 1.8 litres results in lower friction losses and improved thermodynamics, all of which has a positive effect on fuel economy. However, the four-cylinder C-Class models have lost none of their agility and dynamism. This is largely thanks to the compressor supercharger installed in all the new-generation power plants, helping the engine to develop impressive torque from idle. This, in turn, extends the overall ratio by up to 13 %. As a result, the new engines largely run with the throttle wider open, making them particularly economical. This is the so-called Twinpulse effect, providing even higher performance and even lower fuel consumption. The Twinpulse system enables the compressor supercharger and the Lanchester balancer – a combination that is unique in the world – to resolve a further conflict of aims that arises when developing four-cylinder engines: the balancer shafts counterbalance the vibrations which would normally occur, AutoTechnology 4/ 2002
thus ensuring a level of refinement that is exemplary in this displacement class.
Lean-Burn Operation Under Partial Load Major advances in the fields of emission control and engine management have resulted in a solution to a familiar technical problem: producing an engine that is sufficiently lean-burning to provide the desired fuel consumption while using catalytic converters that normally require a "stoichiometric" air/fuel mixture (14.6:1). The solution is a newly developed NOx trap catalytic converter which absorbs the nitrogen oxides during the lean-burn cycle and then rereleases them in brief regeneration phases, so that they react with other constituents of the exhaust gas to form harmless nitrogen. Thanks to this technology, which Mercedes combines with exhaust gas recirculation and secondary air injection in the new direct-injection petrol engine, the C 200 CGI is able to comfortably comply with the future EU-4 emissions standard. Up to 35 % of the exhaust gases can be recirculated, depending on the engine operating charac-
teristics, thus bringing about a substantial reduction in NOx emissions. Another innovation comes in the form of the "linear" oxygen sensor, which becomes active immediately when the engine is started from cold and supplies information about the exhaust gas composition. This information is then processed by the engine computer, for the purpose of warm-up control among other things. It enables the catalytic converter to reach its operating temperature in considerably less time. In addition, a newly developed, electronically networked NOx sensor with digital control is used, to ensure optimum control of the NOx trap catalytic converter.
New MercedesBenz four-cylinder port-injection engine (M 271 KE).
Direct Injection The fuel is injected into the cylinders at an angle of 42 degrees and, depending on the engine operating characteristics, at a pressure of between 50 and 120 bar. The CGI engine has two separate intake ports. These ports ensure optimum swirl in the mixture. Each of the intake ports also has an adjustable swirl flap. The high-pressure fuel pump is driven by the intake camshaft. A pressure regulator controlled by the engine computer regulates the
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High-pressure fuel pump driven by the intake camshaft.
pressure in the fuel rail, which is directly connected to the injectors. This regulator receives signals from a special pressure sensor. Under partial load, at a mean pressure of between 4 and 5 bar and at low engine speeds, the four-cylinder engine is "lean-burning". In other words, it operates with the throttle wider open and with a high level of excess air. Outside this range, the direct-injection engine is operated with the usual air/fuel mixture for engines with catalytic converters (lambda 1).
Aluminium Cylinder Made from high-strength aluminium alloy, the cylinder head in all versions has 16 valves and double overhead camshafts. Unlike in the previous four-cylinder engine, both camshafts are adjustable and have variable valve timing. A newly developed vane-type adjuster with an integrated control valve ensures optimum valve timing at all times. This has a favourable effect on torque characteristics under full
Cutaway view of the new four-cylinder port-injection engine.
load as well as on fuel consumption and exhaust emissions. The valves are controlled by cam followers with a roller mechanism and have a maintenance-free hydraulic valve lifter.
Highly Efficient, LowNoise Compressor The Mercedes-Benz developers have reengineered the compressor by reducing the clearance between the rotors and the supercharger housing and by using a new coating for the rotors. The result is an even higher rate of air flow and even better efficiency than in the mechanical supercharger used in previous Mercedes-Benz four-cylinder engines. Special wide-band silencers are installed on the intake side and pressure side. After being compressed, the air exits the compressor and flows through an intercooler. In this new generation of engines, the standard version and CGI version have different plastic pipe arrangements: in the direct-injection version, they are separated into two separate lines per cylinder before actually entering the cylinder head. Each of these pipes has an electrically adjustable swirl flap which further promotes air swirl.
New Mercedes-Benz four-cylinder direct-injection engine (M 271 DE).
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Electronic Control Unit in the Air Cleaner Housing
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C-Class with the new four-cylinder engine.
The round air cleaner attached to the intake pipe has the advantage of being able to provide a relatively large filter area in the smallest of spaces. In addition, the electronic control unit is located on the side of the air cleaner housing. The control unit is integrated into the vehicle's electronic system via a CAN data bus. The hot-film air flow sensor is positioned directly behind the air filter housing.
Refinement on a Par with a Six-Cylinder Engine The Mercedes engineers claim that the new four-cylinder engines have a refinement and acoustics that are on a par with a six-cylinder engine. This is primarily down to the newly developed Lanchester balancer, which consists of two forged shafts supported in multiple bearings and located below the crank mechanism. The shafts rotate in opposite directions at twice the crankshaft speed and, in doing so, counterbalance the forces of inertia caused, for example, by the motion of the pistons, which tend to cause irritating vibration.
The size, weight and arrangement of the balancer shafts have been perfectly harmonised to neutralise the vibration forces in the four-cylinder engine. This technology thus substantially reduces noise emissions and vibrations. The aluminium housing that contains the bearing-mounted balancer shafts is located in the oil sump and bolted to the crankcase from below. Drive is provided by a newly developed silent chain with low masses. The crankcase also contains the engine oil pump, which is driven by one of the two shafts by means of a gear pair. Made of die-cast aluminium (previous
engine: cast iron), the crankcase is one of the major components in the lightweight design concept. The engine weighs just 167 kilograms, making it 18 kg or almost 10 % lighter than its predecessor.
Lightweight design concept.
Driving Dynamics Mercedes-Benz also offers a newly developed system which recognises individual driving styles and adapts the drive characteristics of the engine accordingly. For sporty drivers, the ECU does its best to please, providing superlative accelerator response. If, on the other hand, the computer detects a driver who prefers comfort rather than speed, it adapts the ECU control characteristics, harmonising the four-cylinder engine settings to suit this particular style of driving. To ensure there is no doubt when detecting the driving style or the driver's requirements, the system monitors the pedal movements extremely closely and records every instance of acceleration before adapting the pedal characteristics.
Cutaway view of the new Mercedes-Benz four-cylinder direct-injection petrol engine. AutoTechnology 4/ 2002
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