CYCLE BY CYCLE VARIABILITY IN EMISSIONS OF A SPARK IGNITION ENGINE.

The exhaust emissions from a single-cylinder spark ignition engine were measured as a function of burning time. Flame propagation time was measured with an ionizabion probe, and the exhaust gas was sampled with a gas sampling valve. Electronic control logic determined the cycles to be sampled, based on the flame propagation time. Tests were carried out at full throttle, for lean, optimum, and rich A/F. The exhaust components measured were CO, HC, O//2, H//2, and N//2 using a gas chromatograph. The emission most affected by CBCV is CO. Cycles that are either faster or slower than the mean cycle have increased CO, particularly at lean A/F where a five-fold difference in CO concentration was measured. HC emissions show a 150% change for the same conditions. For other than lean A/F operation, H//2 was an exhaust product, up to 6% at rich A/F operation.