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This paper describes a technique which can accurately measure firing-cylinder full-load absolute pressure during critical intake events, thereby providing useful cylinder-pressure data for valve-timing optimization. To achieve this, an absolute-pressure transducer is connected to a port drilled through the cylinder wall at an axial location uncovered approximately midway through the piston stroke. This placement spares the transducer from thermal shock caused by flame-front impingement upon the diaphragm, since the combustion is normally completed by the crank angle of passage exposure. The described technique was used to study valve-timing and manifold-runner design effects on the intake process of a V-8 engine and to determine thermal-shock magnitudes and their effect on conventionally-measured pumping-loop data.

An investigation was performed to try to quantify the relative importance of large-scale mixing and turbulence in a multi-valve spark-ignited automotive engine converted to use natural gas fuel. The role of mixing was examined by comparing single-point versus multi-point combustion performance at several operating conditions. The fuel-air mixture passed through a static mixer prior to entering the intake manifold in the single point case. This configuration was assumed to produce a well-mixed charge entering the combustion chamber. The fuel was delivered just upstream of the intake port in the multi-point configuration. The charge was assumed to be stratified in this case. The results showed a significant degradation in combustion stability and maximum power but little difference in ignition delay and fully-developed burn duration using multi-point injection. The relative role of turbulence was examined by altering the intake-flow configuration to create three levels of inlet swirl.