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In a high gas velocity condition in cylinder, the ground electrode orientation of the spark plug causes the ignitability to fluctuate due to the change in gas flow around the spark gap. As one method to solve this issue we have focused on controlling the gas flow by plate like airfoils or turbine blades. We have developed gas flow control technology for the spark plug to achieve high ignitability under the worst case condition of ground electrode orientation. The adoption of current ground electrode welding technology has allowed us to locate a flow guide plate on the plug housing.

Improving the engine efficiency to respond to climate change and energy security issues is strongly required. In order to improve the engine efficiency, lower fuel consumption, and enhance engine performance, OEMs have been developing high compression ratio engines and downsized turbocharged engines. However, higher compression ratio and turbocharging cause cylinder pressure to increase, which in turn increases the demand voltage for ignition. To reduce the demand voltage, a new ignition system is developed that uses a high voltage Zener diode to maintain a constant output voltage. Maintaining a constant voltage higher than the static breakdown voltage helps limit the amount of overshoot produced during the spark event. This allows discharge to occur at a lower demand voltage than with conventional spark ignition systems. The results show that the maximum reduction in demand voltage is 3.5 kV when the engine is operated at 2800 rpm and 2.6 MPa break mean effective pressure.