Search Results

The objective was to develop a modem engine to succeed the M 102; 2.6 million of these units were made between 1979 and today making it the most successful Mercedes-Benz four-cylinder petrol engine to date. The new M 111 coordinated production set-up together with the familiar M 104 six-cylinder four-valve engines and the 600 diesel series. Emphasis has been deliberately given to improved torque rather than very high volumetric efficiency. This has made it possible to apply four-valve technology, which was originally only to be found in motor racing, in such a way that ordinary customers can benefit form advantages such as high torque and raised power output, as well as reduced fuel consumption and emissions. Extensive noise-reducing measures in the engine ensure that, despite the higher power output and lower engine weight, noise levels have also been improved.

This paper shows that the functional integration of Electronic Throttle Control (ETC) into the engine control strategy allows improvements of emissions and fuel economy without making compromises in respect of driveability. A cost effective way for realizing ETC is the integration of the control electronics into the engine control unit (ECU). The paper describes the consequences of such an integration for the ECU hardware and software. Special attention is given to the ETC related safety aspects. Another chapter discusses different technologies for the throttle actuator drive. This is followed by a brief description of a suitable control strategy for a throttle actuator. Finally the paper gives also an overview about current status and development trends of accelerator pedal sensors necessary for ETC.

In a previous paper (SAE 951035) Daimler-Benz and Shell advocated that fixed oil drain intervals should not exceed 15,000 km or annually. This paper describes further experience, with data from various field trials and engines, allowing engine condition to be considered in relation to lubricant ageing and condition. Based on this Mercedes-Benz have introduced ASSYST, a new passenger car maintenance system which processes customer-specific operating data and calculates oil change intervals. Unnecessary oil changes are avoided, conserving resources, and changes are not overlooked assuring durability. Intervals between 15,000 and 30,000 km are enabled, corresponding to between 1 and 2 years, representing a time extension of about 50%. Premium quality oil permits a longer interval, thus the customer sees an immediate benefit. This study shows that lubricant continues as an important engine design element and illustrates the environmental commitment shared by both companies.

Lubrication of moving parts becomes less efficient in those areas where close fit limits the amount of lubricant to a very thin oil film. Journal bearings are particularly vulnerable in this respect. To test the degree of wear, a radioisotope technique was applied in which shafts and bearings were deuteron activated. Not only did the tests prove sufficiently sensitive to determine the full range of hydrodynamic lubrication, but they also identified the transition point at which poor lubrication caused journal-bearing wear. It was also found that materials of the shaft and bearings greatly influenced the amount of wear.

Conventional direct injection diesel engines for cars or light duty trucks, equipped with injection pumps of conventional types, such as distributor injection pumps and inline injection pumps, and operating at compression ratios of 18-19, are capable of offering a fuel consumption benefit of some 15% compared to chamber diesel engines. In terms of noise and exhaust emissions, and also black smoke characteristics, however, they are significantly inferior to the prechamber engine. In addition, they have a specific rated output which is some 20% lower. Only through the use of a compression ratio of 21 and high injection pressures it is possible to measurably diminish the drawbacks in respect of exhaust emissions and, to some extent, in respect of soot emissions. This in no way enhances the noise behaviour, though. For this reason, it is essential to employ measures such as injection rate shaping or split-injection.