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Technical Paper

Analysis of a Stratified Charging Concept for High-Performance Two-Stroke Engines

This paper presents the results and conclusions from a conceptual design study for a stratified charging concept. The stratified charging engine has a displacement of 64 cm3 and a four-port design with reed valves at two ports to control the bypass air. During the intake stroke of the engine, bypass air is sucked into the transfer ports to purge the air-fuel mixture present in the ports from the previous stroke back into the crankcase. This fills the transfer ports near the exhaust with pure air at the beginning of the scavenging stroke. During scavenging, the bypass air is ejected in the cylinder, shielding the exhaust against the fresh mixture coming from the ports on the intake side. This allows the hydrocarbon emissions to be reduced by over 40 %. The conceptual design study is based on an analysis of the mixture short-circuiting mechanisms and CFD investigations of the scavenging flow with charge stratification.
Technical Paper

Exhaust Emission Control on the New 500 SL and 500 SL Structure and Mode of Operation

This paper describes the exhaust emission control system designed for the new Mercedes-Benz sports car generation 300 SL and 500 SL, Remarkable features of the catalytic converters are maximum environmental compatibility, i. e. minimum of emission and noise under all driving conditions. By reduced back-pressure, they also contribute greatly to the well known requirements of a sports car: high performance and high torque over the entire engine-speed-range. Apart from an effective exhaust gas aftertreatment, great efforts were made to prevent the formation of pollutants under all driving conditions. This work is done by intelligent motor management consisting of digital spark control, mechanical-electronic injection, variable valve timing and EGR.
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.