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CARS temperature measurements were carried out both in a constant volume combustion chamber and in a spark-ignition engine. The CARS temperature measurement under engine-like condition was validated by comparing the unburned gas temperatures for premixed propane-air flame in a constant volume combustion chamber obtained by CARS with predicted temperatures of 2-zone flame propagation simulation model. There was good agreement between the predicted temperatures and the mean values of 10 CARS measurements. The standard deviation of 10 measurements at each measuring timing was about ±40 K. End-gas temperatures were measured by CARS technique in a conventional 4-cylinder DOHC spark-ignition engine with the engine motoring and firing. The measured motoring temperature matched well with the adiabatic core temperature calculated from the measured cylinder pressure. The engine was fueled with primary reference fuel (PRF80) of 80% iso-octane and 20% n-heptane by volume.

A computational fluid dynamics (CFD) prediction of the transient flow in the intake system of a spark ignition engine is compared to experimental data. The calculation was performed for a single cylinder version of a pre-1995 Ford two-valve production engine, while experiments were carried out on a single cylinder Ricardo Mark 3 research engine with similar overall geometric parameters. While the two engines have somewhat different geometries, this was not considered to be a significant problem for our study of flow features. Both set-ups employed gaseous fuel. The calculation was performed using the commercially available Star-CD code incorporating the complete intake manifold runner and cylinder into the mesh. Cylinder pressures were in good agreement with experiment indicating that wave dynamics were well captured. Comparison was also made to the measured instantaneous gas temperatures along the intake system.

An experimental and analytical study was conducted to investigate the effects of load control with port throttling on stability and fuel consumption at idle. With port throttling, the pressure in the intake port increases during the valve-closed period due to flow past the throttle. If the pressure in the port recovers to ambient before the valve overlap period, back flow into the intake system from the cylinder is eliminated. This allows increased valve overlap to be used without increasing the residual mass fraction in the cylinder. Results showed that, with high valve overlap and port throttling, idle stability and fuel consumption can be maintained at values associated with low overlap in a conventionally throttled engine. However, implementation of this concept in production is regarded to require precision-fit and balanced port throttles, an external vacuum pump for vacuum systems support, and revision of the PCV system.