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This paper describes an investigation of one operating point of the transient warmup curve of a gasoline engine. Coolant liquid and oil of this engine have been cooled down to a constant low level in order to perform detailed measurements and an analysis of this particular warmup point. The influence of low coolant temperature, different pressure drop in an air assisted fuel injection system and a variation of ignition angles on specific fuel consumption, exhaust emissions, energy conversion etc. will be shown. The results show that the suggested test procedure (keeping the coolant temperature at a constant low level) provides the possibility to simulate the behaviour of an engine with air assisted fuel injection during warmup. During this warmup period it is desired to run the engine with retarded ignition timing to realize a fast catalyst warmup.

This paper describes the influence of a rapid throttle opening on the charging process, the mixture formation, the ignition timing and the transient performance of an engine. The two main reasons for disturbances in the transient response are imperfections in mixture formation and in ignition timing. These phenomena will be analysed using a single cylinder and a four cylinder engine. For the single cylinder engine a detailed analysis of every cycle is possible during a rapid throttle opening. This will be done by computations, using measured initial and boundary conditions in order to show the variation in the air-fuel equivalence ratio during the transient. For the 4 cylinder engine it is almost impossible to carry out the same detailed analysis, because it is difficult to estimate the individual volumetric efficiency of each cylinder.

This report describes the attempt to increase the torque in the lower rpm range of a small 1.3 l four stroke engine without reducing the torque and the power of 50 kW/l. The goals are met by using a camshaft with relatively large valve overlap and reed valves in the intake manifold. With this assembly the engine delivers 84.5 % of maximum torque at 1000 rpm, 92.2 % at 1500 rpm and 98 % of maximum torque in the range from 2500 rpm to 5000 rpm. In comparison to mass production engines the maximum torque of 116 Nm is on a current level while a torque of 84.5 % of the maximum torque at 1000 rpm is about 10 to 15 % higher. The investigation of different camshafts and intake manifolds with and without reed valves will be described in this paper.