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The development of a plasma jet ignition system is described on a 4-cyl, 140 in3 engine. Performance was evaluated on the basis of combustion flame photographs in a single-cylinder engine at 20/1 A/F dynamometer tests on a modified 4-cyl engine, and cold start emissions, fuel economy, and drivability in a vehicle at 19/1 air fuel ratio. In addition to adjustable engine variables such as air-fuel ratio and spark advance, system electrical and mechanical parameters were varied to improve combustion of lean mixtures. As examples, the air-fuel ratio range was 16-22/1, secondary ignition current was varied from 40 to 6000 mA, and plasma jet cavity and electrode geometry were optimized. It is shown that the plasma jet produces on ignition source which penetrates the mixture ahead of the initial flame front and reduces oxides of nitrogen emission, in comparison to a conventional production combustion chamber.

The US EPA 40CFR certification label fuel economy mpg for 114 model types of 1998 model year passenger vehicles marketed in the United States (US) by European. Pacific Rim, and American manufacturers, was correlated with fuel economy mpg test data obtained by the Consumers Union (CU) of US, Inc., a nonprofit, independent consumer information organization. The 114 model types range in curb mass (empty weight) from 916 kg (2015 lbs) to largest 2425 kg (5335 lbs). This correlation shows that the manufacturers US EPA label values overstate city mpg and understate the highway mpg significantly; in comparison to the CU city mpg and CU highway mpg test data, for the 114 model types of motor vehicles, reported by Consumers Union in 1998.