Mercedes C200 CDI Review

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Posted on: Jul 04 2007

Mercedes-Benz C200 CDI

We had then bemoaned the lack of power in the petrol-engined car and been enamoured with the power, torque and above all, the efficiency of the diesel. Since then we have lived with the C200 CDI through one of our four-season long term tests while DaimlerChrysler India started making the C200K in India to add the much required boost to the petrol engined.

Even though one could not fault the C200 CDI in any respect, especially in terms of power or torque, that is no reason for DaimlerChrysler to stop the march of technology. In its continuous process of technology development, the company came up with its second generation of common rail direct injection diesel technology which was first used in the E-class (road test in the June 2003 issue of OVERDRIVE) and which has now found its was into the C-class.

The exteriors and the interiors of the car remain basically the same as the one we had with us. Although we were expecting clear glass headlamps on the C220 CDI like we have seen on some of the imports, DaimlerChrysler India decided to go along with the normal headlamp glass for the time being. The car is also now being fitted with the aero-wipers which have already proved their worth in the other model series.

The one most significant change in the equipment levels of the car is the provision of a new music system. The change is that now instead of a cassette, the system has a slot for a CD. I guess that is in keeping with the profile of the C-class user. This in addition to the CD changer that is fitted in the glove compartment of the car.

Since there are no other changes in the car we will move to those aspects of the car that are changed.

Engine & Transmission

The basic engine remains the same. With each cylinder still having the same bore and stroke dimensions of 88mm and 88.3mm respectively and the displacement of four cylinders adding up to 2148cc, there is not much physical change to the engines. That apart the figures tell a completely different story. As compared to the C200 CID there is 21 per cent more power and 36 per cent more torque. Maximum power is now 142PS coming in at 4200rpm while the maximum torque of 340Nm is available across a 500rpm band, from 1800rpm to 2300rpm, compared to the 115.6PS of maximum power and the 250Nm of maximum torque which was generated at a much higher 2300rpm and available for 500rpm until 2800rpm.

Compared to the first generation common rail 220 engine that was available on the E-class, the second generation technology allows the engine to develop an extra 25Nm of torque while the power output remains nearly the same.

The change in figures tells a very small part of the story of the move to the second generation of common rail technology. As we and detailed in the road test of the new E220 CDI numerous aspect of this four-cylinder 2148cc engine have been modified and 80 new components have been used. Apart from the visible-in-figures difference there is also major improvement in terms of fuel efficiency, emission characteristics and comfort.

The majority of these have been achieved by increasing the pressure in the common rail system from 145bar to 155bar resulting in a further optimisation of the charge cycle in the cylinders. The maximum injection pressure has also been increased from 1350 to 1600bar. The old six-hole injection nozzle has been replaced by a seven-hole one. The new injector enables a 20 per cent reduction in the size of the nozzle hole diameter. Consequently, the fuel is even more finely dispersed in the combustion chambers and the efficiency of combustion is further improved.

Particulates thus account for a much lower percentage of the exhaust gases. However, as mentioned in the road test of the E220 CDI, the greater flow restriction, due to the smaller nozzle holes, prolongs the injection period, which would have had a particularly adverse effect when power delivery requirements are high but this problem has been nipped in the bud by the increase in the injection pressure.

The problem with direct injection engines, despite their efficiency and good torque output has always been NVH and the solution to this problem for long has been pilot injection, something that Mercedes-Benz has worked on extensively in the development of its second generation of common rail direct injection diesel engines. Using double pilot injection made possible by the even more powerful solenoid armature in the new 1600bar injectors, considerably shorter intervals have been achieved between pilot and main injection. This now means that a small quantity of fuel flows into the combustion chamber twice in quick succession - within a millisecond so as to ensure even better pre-heating. The difference is audible: combustion noise has been dramatically reduced. This is also the first four-cylinder diesel engine which Mercedes has equipped with two balancer shafts which counter-rotate at twice the crankshaft’s speed. This allows them to compensate for the inertia forces which occur naturally as a result of the pistons’ movements and which can cause irritating vibration. The clear reduction in noise and vibration levels resulting from this technology translates into a considerable improvement in ride comfort.

Like the V8 diesel engine in the S-class this four-cylinder engine is also fitted with a VNT turbocharger with electrically adjustable guide vanes. This enables more dynamic and precise supercharging than the previous vacuum controlled system. The effect is the ability to build up the charge pressure faster and therefore substantially more pulling power as shown by the reduction in rpm at which the maximum torque is generated.

The C200 CDI was a quiet car and the company claims that the C220 CDI is even more refined. When one is reaching those levels of perfection, there is not much that the human senses can discern, so we will take DaimlerChrysler's word for it.

We tested the C220 CDI with a six-speed manual gearbox which is slick shifting and ideal for the character of the car. The ratios are very well sorted to keep the car in the meaty part of the power band. The C220 CDI is also available with the five-speed automatic transmission that our long term C200 CDI came equipped with.

Fuel Efficiecy
Before we start talking about fuel efficiency it would do well to remember that this is a very heavy car, at 1520kg it is heavier than even the C200 CDI. Aspi cruised between 80 and 100kmph in 6th gear for the highway fuel efficiency test. At those speeds the engine ticks over effortlessly at about 1800rpm in 6th gear and after the 102km run the car took in 4.97 litres of fuel. Divide the distance by the fuel consumed to get 20.52kmpl fuel consumption. Astounding? In the city, with the air con turned on in the blazing Pune sun, the car returned 10.25kmpl. Using our 75 per cent city driving and 25 per cent highway driving formula, the overall fuel efficiency works out to 12.82kmpl giving the car a range of 897km.

Verdict

The C200 CDI had a good engine and the C220 CDI engine is even better. It is quieter, it is more powerful, it pollutes less and is more fuel efficient.
And at the same time we should not forget about the car - though slightly cramped for space at the rear, it is one of the safest cars on the road, loaded with equipment and comfort features and of course the three-pointed star.