In-Cylinder HC Measurements with a Piston-Mounted FID

A fast-FID sampling technique has been developed to study top-land crevice out-gassing from the moving piston of an SI engine. A sampling probe, housed in the piston crown, delivered gas to the FID head via a flexible transfer tube. Comparisons of the HC concentrations at the top-land location and the bulk gas above the piston crown confirm that HC material is out-gassed from the top-land region during the expansion stroke and is followed by more rapid out-gassing after EVO. The removal of wall HCs has been detected during the exhaust stroke from the probable scrolling effect produced by the rising piston scraping unburned material from the cylinder wall.