Cycle by Cycle Variability in Emissions of a Spark Ignition Engine

E. E. Milkins; H. C. Watson; L. C. Goldsworthy; R. J. Hallworth

doi:10.4271/741034

1974-02-01

Cycle by Cycle Variability in Emissions of a Spark Ignition Engine 741034

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 ionization 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, O₂, H₂, and N₂ 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, H₂ was an exhaust product, up to 6% at rich A/F operation.

It is well established that reductions in CBCV would improve efficiency and power output. Here it is established that a reduction in CBCV would also reduce overall CO and HC emissions, particularly for very lean operation.

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Cycle by Cycle Variability in Emissions of a Spark Ignition Engine 741034

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