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A new fast response NO detector, based on the chemiluminescence (CLD) method has been used to measure continuous, real time levels of NO in the cylinder, and simultaneously in the exhaust port of a virtually unmodified production SI engine. The real time NO concentration data show a great deal of information. Simultaneous NO measurements taken in-cylinder at sample points a few millimetres apart show substantial differences. Exhaust and in-cylinder levels from the same cycle show even greater differences, though the levels on average are well correlated.

This paper describes the application of a non-dispersive infrared-based instrument designed to measure CO with a response time of 7ms. Spark ignition engine emission measurements recorded during the first 505 seconds of an FTP75 drive-cycle for a 4 cylinder engine are presented, including fast response hydrocarbon and NO measurements. An analysis of the engine-out (pre-catalyst) exhaust gas is provided. Data collected simultaneously with a standard emissions test stand and conventional dilution tunnel are compared to the high frequency measurements. Fast CO analysis provides new insight into cold-start fuelling calibration and cylinder-to-cylinder AFR variation. Under rich conditions, the strong dependence of CO production on the quantity of excess fuel allows a significantly faster estimate of engine stoichiometry than a UEGO sensor.

A fast response sensor for measuring carbon dioxide concentration has been developed for laboratory research and tested on a spark ignition engine. The sensor uses the well known infra-red absorption technique with a miniaturized detection system and short capillary sampling tubes, giving a time constant of approximately 5 milliseconds; this is sufficiently fast to observe changes in CO2 levels on a cycle-by-cycle basis under normal operating conditions. The sensor is easily located in the exhaust system and operates continuously. The sensor was tested on a standard production four cylinder spark-ignition engine to observe changes in CO2 concentration in exhaust gas under steady state and transient operating conditions. The processed sensor signal was compared to a standard air-to-fuel ratio (AFR) sensor in the exhaust stream and the results are presented here. The high frequency response CO2 measurements give new insights into both engine and catalyst transient operation.