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The combustion process in an IC engine is of significant importance for its noise and vibration characteristics in the vehicle. Describing the combustion process with thermodynamic metrics typically demands extensive instrumentation of the engine to obtain the cylinder pressure from the combustion chamber. This time consuming task often requires, that the engine be removed from the vehicle, instrumented with pressure transducers, and then either reinstalled in the vehicle and tested or installed in a test cell and evaluated. This paper describes a new relatively simple approach towards examining important combustion parameters. The technique is based on statistical analysis of the crankshaft's speed fluctuation. This approach requires relatively simple instrumentation of the engine and is therefore more applicable for vehicle level investigations.

Cylinder air/fuel ratio distribution is an important factor affecting the economy, power, vibration, and emissions of an internal combustion engine. Currently, production automobiles utilize an exhaust gas sensor located in the main exhaust stream in order to regulate air/fuel mixtures. By measuring the oxygen content of the exhaust gas for each cylinder independently, the degree of air/fuel variation between cylinders can be determined. This information can be used to determine the mixture quality of specific cylinders. Knowing these variances can lead to design changes in the intake and exhaust manifolds as well as better control of fuel metering which will improve the output of the engine. This study was carried out using a 1991 3.8L Buick V-6 engine with customized exhaust manifolds utilizing exhaust gas oxygen sensors for each cylinder in addition to the sensor located in the main combined exhaust gas stream. Production level, ZrO2 sensors were used for this experimental study.