In the compression and combustion strokes different individual hydrocarbons are generated through a complex reaction chemistry and can be monitored by a rapid V&F multicomponent gas analyzer system. They give detailed information on the physical properties of an engine.
Through all different reaction sequences of the combustion, surface quenching reactions leave a characteristic pattern of hydrocarbons in the exhaust gas. Toluene and xylene, for example, represent direct monitors for unburnt fuel, alkenes and alkines show thorough fuel decomposition, allowing a rapid combustion when the spark is ignited, whereas aldehydes indicate autoignition processes.
Ratios of hydrocarbon concentrations describe engine parameters like fuel/air mixing properties, EGR characteristics, autoignition processes, and engine oil combustion. So an optimized engine performance can be set by the hydrocarbon pattern measured in the direct exhaust gas.