Measuring the effect of spark plug and ignition system design on engine performance

Measurement of work produced during a power stroke was discovered to be an effective indication of combustion variation. Simultaneous measures of engine emission levels provide data on the effects of spark plug and ignition system variables. Extended gap locations, wider gap size, and higher spark energy levels are the most significant parameters that reduce the cyclic combustion variation and the unburned HC. Smaller electrode size shows similar effects, but these effects are less pronounced. The performance of surface gap plugs does not equal that of standard air gap spark plugs.