Mercedes Benz C-Class (2002)

Hot on the heels of the C-Class range re-positioning, which saw the introduction of SE packages and more value to customers, and the Saloon's five star Euro NCAP crash test performance, Mercedes Benz has introduced an innovative range of TWINPULSE petrol engines for the C-Class.

The engines use four-cylinder technology combined with efficient superchargers, intercooling, variable valve timing, Lanchester balancer shafts and adaptive drive dynamics. All these features add up to silky-smooth engines with high power outputs, strong torque curves and remarkably low CO2 emissions. This major reduction is great news for fleet users, who will now pay significantly less tax.

The new engines retain the recently realigned C-Class prices - so customers win in their pocket and under the bonnet. The new TWINPULSE engines will be available in C-Class Estate and Sports Coupé models from July, and in C-Class Saloon models from September.

CO2 emissions down to start from 175 g/km - users now pay 37% less tax

Fleet users will appreciate one of the main benefits of the new TWINPULSE system. Carbon dioxide emissions for the entry-level manual C 180 KOMPRESSOR are just 175 grams per kilometre - an incredible 50 g/km lower than the previous car's figure. It means that for the period 2002-2003, business users will now only be taxed on 17 per cent of the car's value - a 10 per cent reduction on the previous entry figure of 27 per cent.

Company car users paying the higher rate of income tax used to pay £2263.68 for an entry-level C180 Classic Saloon. With the new prices, the C 180 KOMPRESSOR Classic Saloon now costs the same user just £1347.70 per year - a reduction in tax of £915.98. Over a typical ownership period (36 months), the new C 180 KOMPRESSOR Classic Saloon offers a tax saving of an amazing £2775.32 compared with the previous C 180 Classic Saloon. A more detailed analysis of these figures is shown at the end of the release.

Win with the tax man, win at the pumps

In addition to their low carbon dioxide levels, the TWINPULSE engines offer improved fuel consumption. Using the new C 180 KOMPRESSOR as an example, the new engine returns a combined figure of 38.7 mpg (28 per cent better than the equivalent 30.1 mpg for the previous car). This gives a new theoretical range of 527 miles - 117 more than before.

These fuel savings are shown across the entire C-Class TWINPULSE range - technical specifications of which are shown at the end of this release.

Output range of the new four-cylinder engines from 143 to 192 hp

Three versions of the new Mercedes four-cylinder engine are available, two in the Saloon and Estate, one high performance variant in the Sports Coupé. All engines share the same capacity - 1796 cc - but the power and torque outputs differ.

The new C 180 KOMPRESSOR has an output of 143 hp (at 5200 rpm) and a maximum torque of 220 Nm (between 2500 and 4200 rpm), 15 per cent more than the preceding model.

The Saloon is 1.3 seconds faster than the previous C 180 when accelerating from standstill to 62.5 mph. It also has an eight mph higher maximum speed (now 139 mph).

The new 163 hp (at 5500 rpm) C 200 KOMPRESSOR unit develops 230 Nm of torque between 3000-4000 rpm. The fuel consumption advantage over the preceding model is more than 12 per cent (now 32.8 mpg combined).

C-Class Sports Coupé models also include the 192 hp (at 5800 rpm) C 230 KOMPRESSOR unit. Developing 260 Nm between 3500-4000 rpm, carbon dioxide emissions are 43 grams per kilometre better than before. Fuel consumption improves by over seven per cent to a combined figure of 30.7 mpg. Saloon and Estate models retain their six-cylinder C 240 engines, rather than introducing this derivative.

How TWINPULSE works - the science bit

The new range of engines marks a radical step for Mercedes Benz, as they combine the advantages of both four- and six-cylinder powerplants.

The company's engineers have ensured that the new four-cylinder engines deliver improved 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 the fuel economy.

However, the four-cylinder C-Class models have lost none of their agility and dynamic character. This is largely thanks to the crankshaft-driven Eaton-type supercharger installed in all the new engines, which helps the engine to provide impressive torque from idle. As a result, the new engines largely run with the throttle wider open, making them particularly economical. This is the TWINPULSE effect: even higher performance and even lower fuel consumption.

The TWINPULSE system enables the supercharger and the Lanchester balancer - a world-first combination - to work together. The balancer shaft reduces the vibrations that normally occur in a four-cylinder engine.

In other words, mechanical supercharging and sophisticated engine technology enable the new Mercedes Benz engines to combine the tractive power and the low-noise characteristics of a six-cylinder engine with the economy of a four-cylinder unit.

Aluminium cylinder head and variable valve timing

Made from high-strength aluminium alloy, the cylinder head in all versions of the new TWINPULSE engine has 16 valves and double overhead camshafts. Unlike in the previous four-cylinder engines, 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 load as well as on fuel consumption and exhaust emissions. The valves are controlled by means of cam follower with roller mechanism and have a maintenance-free hydraulic valve lifter.

Highly efficient, low-noise supercharger

The engineers have also re-engineered the supercharger - which ensures exemplary bottom-end torque characteristics in all new TWINPULSE four-cylinder engines - 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 greater 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, thus reaching the optimum temperature and density for the efficient combustion.

Electronic control unit in the air cleaner housing

The round air cleaner attached to the intake pipe has the advantage of being able to provide a relatively large filter area in a small space. In addition, the electronic control unit - equipped with two powerful processors - is located on the side of the air cleaner housing.

The two processors share the complex tasks: one is responsible for real-time processes, such as calculation of the ignition and injection pulses, whilst the other deals with time-synchronised tasks such as lambda control or determining the ignition timing and the injection quantity.

The control unit is integrated in the vehicle's electronic system via CAN databus (Controller Area Network) and swaps data with other microcomputers. The hot-film air flow sensor, incorporating re-engineered functions, is positioned directly behind the air cleaner housing.

As is the case in all state-of-the-art petrol engines from Mercedes Benz, the new four-cylinder generation uses electronic monitoring for components that have to function correctly in order to ensure low emissions. This on-board diagnostic system permanently monitors catalytic converter efficiency and the ignition system as well as checking the oxygen sensor.

The "Check Engine" display on the instrument cluster lights up if a fault occurs in one of these systems. Meanwhile, details of any malfunctions are stored so service engineers can detect the problem immediately and remedy the fault.

Six-cylinder refinement thanks to the newly-developed balancer shaft

Alongside great power delivery, low fuel consumption and low exhaust emissions, the new TWINPULSE four-cylinder engines have a further advantage - refinement and acoustics

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, located below the crank mechanism.

The shafts rotate in opposite directions at twice the crankshaft speed and, in so doing, counter-balance the inertia forces caused by the motion of the pistons which tends to cause vibration.

The size, weight and arrangement of the balancer shafts have been developed to neutralise the vibration in the four-cylinder engine. This technology substantially reduces noise emissions and vibrations, and therefore enhances ride comfort.

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 diecast aluminium (in the previous engine it was cast iron), the crankcase is one of the major components in the lightweight design concept at the heart of the new four-cylinder engine. Again the figures speak for themselves: the unit weighs just 167 kilogrammes, making it much lighter than its predecessor. The actual weight saving equates to 18 kilogrammes or almost 10 per cent.

Driving dynamics tailored to driver requirements

Mercedes Benz also offers a newly developed system which recognises individual driving styles and adapts the drive characteristics of the engine accordingly, further adding to the dynamic driving experience. For those that fancy themselves as racing drivers, the ECU does its best to accommodate, providing excellent accelerator response. If on the other hand the computer detects a driver looking for 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. This is a continual step-by-step process which ensures that the driving characteristics never contradict the driver's expectations.

In the case of a sporty driving style, the pedal characteristics change so that, although pedal travel may remain the same, the throttle valve is opened further than would usually be the case. The engine therefore reacts quicker to driver input and is quicker to provide maximum acceleration. If a more comfort-oriented driving style is detected, the ECU sets flatter pedal characteristics. In this instance, although the pedal travel remains the same, the throttle valve opens more slowly than usual and acceleration is more "gentle".

More TWINPULSE engines arriving later in 2002

In addition to the imminent introduction in the C-Class range, TWINPULSE engines will also be available in CLK 200 KOMPRESSOR Coupés and E 200 KOMPRESSOR Saloons by the end of the year.

New re-aligned Mercedes Benz C-Class Saloon company car tax liabilities
Vehicle Model P11D Value CO2 Emissions Tax Band 2002/3 Annual Tax Liability Annual Tax Liability 40%
£20,960.00 >225 27% £5,659.20 £2,263.68
£22,410.00 227 27% £6,050.70 £2,420.28
£19,819.12 175 17% £3,369.25 £1,347.70
£21,464.00 175 17% £3,648.88 £1,459.55
£21,464.00 202 22% £4,722.08 £1,888.83
Vehicle Model P11D CO2 Emissions Tax Band 2002/3 Annual Tax Liability 40% Tax Band 2003/4
£20,960.00 225 27% £2,263.68 29%
£22,410.00 227 27% £2,420.28 29%
£19,819.12 175 17% £1,347.70 19%
£21,464.00 175 17% £1,459.55 19%
£21,464.00 202 22% £1,888.83 24%
Figures shown in grey are old models
Old model values from TopCalc
New model values are basic list price + delivery charge of £395 + VAT

Published : 08/07/02 Author : Melanie Carter

Mercedes Benz C-Class News

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