Improving the torque characteristic of a small four stroke four cylinder engine by using reed valves in the intake manifold

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.