Comparison of the Cyclic Variability of an Exhaust Gas Temperature Sensor and In-Cylinder Pressure Measurements

This paper presents a concept of an exhaust temperature sensor as a method to monitor cyclic variability of combustion. The goal is to determine if the cycle-to-cycle fluctuations of the sensor can be related to the cyclic variability of combustion as measured by a pressure transducer. Experiments were conducted with a port fuel spark ignition engine at different engine speeds and loads. For each operating point, different spark timing and different excess ratios were used to evaluate the sensitivity of the temperature-based sensor to quantify the cyclic variability of combustion as measured by the Coefficient of Variation (COV). The results demonstrated the sensitivity of the concept to relatively low levels of cyclic variability (circa 1–3% COV of IMEP). At a given speed and load, changes in cyclic variability indicated by in-cylinder pressure measurement were, in general, reproduced by the sensor. The relationship between the cyclic variability indications provided by the two sensors varied as the speed and load were changed.