Cyclically Resolved HC Emissions from a Spark Ignition Engine

A high frequency response (300Hz) flame ionization detector has been used to measure the instantaneous level of HC emissions in the exhaust of an SI engine. The characteristics of the HC signal are observed to be stable and repeatable at mixture strengths around stoichiometry, but at lean mixtures more erratic and complex signals are observed. With the addition of information on cyclic work and ionization levels in the exhaust, a detailed insight into lean combustion problems can be obtained.