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Technical Paper

Extended Oil Drain Intervals - Conservation of Resources or Reduction of Engine Life (Part II)

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.
Technical Paper

Extended Oil Drain Intervals: Conservation of Resources or Reduction of Engine Life

: Over the last 40 years it has been possible to lengthen recommended passenger car engine oil drain intervals by up to five times, despite the substantial increases in oil stress through continously rising demands on performance and environmental acceptability. Behind this considerable progress lie improvements in engine design and production technology and the development of suitable advanced engine oil formulations. With increasing oil drain intervals comes a growing uncertainty as to exactly when the oil change should best be made: a fixed mileage applicable to all vehicles is preferred for its practicality but the optimum depends on the driving history of individual vehicles. In Europe a 15000 km oil drain interval is now normal. A further extension based on a fixed interval would give an advantage to a minority of customers but could seriously compromise the durability of engines in the overall vehicle population.
Technical Paper

Concepts for Ultra Low Emission Vehicles

To achieve low emission levels, the handicap of the TWC is its light-off characteristic. It achieves a maximum hot efficiency of nearly 100 %, but this requires a temperature in the range of 300 to 450 °C. To improve this time lag after cold start, the TWC needs additional help to reach the targets of future low (LEV) or ultra low emission (ULEV) levels. This paper describes the work on additional devices to reach the ULEV-levels such as: Electrical Heated Catalyst (EHC). Burner Heated Catalyst (BHC) Hydrocarbon Trap (HCT) as external device. Adsorber Coated Substrate (ACS) in the usual converter box. The comparison of these systems was done with a concept car. The low mileage exhaust results demonstrated the principal suitability of all these devices, but there is still much work to be done to meet the ULEV levels with the guaranted durability. The advantages and disadvantages of the systems are discussed, including estimated weight and cost.
Technical Paper

Secondary Air Injection with a New Developed Electrical Blower for Reduced Exhaust Emissions

Secondary air injection after cold start gives two effects for reduced exhaust emissions: An exothermic reaction at the hot exhaust valves occurs, which increases the temperature of the exhaust gas. It gives sufficient air to the catalyst during the cold start fuel enrichment that is necessary to prevent driveability problems. Handicaps for the wide use of air injection include space constraints, weight and price. An electrical air blower was choosen to best satisfy all these requirements. The development steps are described. The result is a three stage radialblower with extremly high revolutions of about 18000 rpm. The system configuration and the outcome are demonstrated on the new C-Class of Mercedes-Benz. The results show emission reductions higher than 50 %, while also satisfying the development goals of noise, volume, weight and cost requirements.
Technical Paper

Further Development of the Six-Cylinder Engines

When Mercedes-Benz enhanced its mid-series in autumn of 1992, the previously installed six-cylinder engine with four-valve technology and 3.0 litres total displacement [1] was replaced by the four-valve engine with 3.2 litres total displacement familiar from the new S-class [2]. For this application, the engine was subjected to still further development in terms of combustion mixture preparation and engine management, and a variant with a total displacement of 2.8 litres was added. This engine replaces the engines of 2.6 total displacement [3]. This further development, and the new engine, are described below.
Technical Paper

Design and Mechanics of the Four-Cylinder Engines with 2.0 and 2.2 Litres Displacement

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.
Technical Paper

The Engine Management System of the New Mercedes-Benz S-Class

Abstract The engine management system of the new Mercedes-Benz S-class has been completely redesigned and fully meets the demands of the new top models. The ignition management, fuel injection management and air management system components are interlinked by a high-speed serial databus, controlling functions are performed in real-time and parallel. Open system architecture and a suitable communication structure indicate how engine management systems will be designed in the future.
Technical Paper

The Influence of High Pressure Fuel injection on Performance and Exhaust Emissions of a High Speed Direct injection Diesel Engine

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.
Technical Paper

Relationship Between Oil Film Thickness and Wear of Journal Bearings

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.