Microwave Discharge Igniter (MDI) is an ignition device that operates based on the microwave resonance phenomenon. Receiving the microwave pulses from a semiconductor generator, the MDI generates non-thermal plasma to enhance the combustion. A new igniter plug consists of multiple MDIs in its structure is developed to achieve leaner operation limit as well as higher dilution limit, which are essential strategies to meet current and future emission regulations. The prototype multi-point MDI plug contains 3 separate MDI port which are all connected and controlled by the semiconductor MW generator. The prototype 3-point MDI is tested in both a single cylinder performance engine and a production multi-cylinder engine. At target conditions of part load and low load, low engine speed, the multi-point MDI performs much better than single MDI and the traditional spark plug in both engines. In the performance engine, the 3-point MDI results in the shortest burn duration especially during the early stages. However, the 3-point MDI exceeds the lean running capability of the production engine when operate as a plug with two active MDI ports and hence the full potential of 3-point MDI currently exceed the current generation of production engines.

微波放电点火器（MDI）是一种基于微波共振现象而工作的点火装置。MDI接收来自半导体发生器的微波脉冲，产生非热等离子体以增强燃烧。开发一种新型点火器塞，其结构中包含多个MDI，以实现更窄的运行极限和更高的稀释极限，这是满足当前和未来排放法规的重要策略。原型多点MDI插头包含3个独立的MDI端口，这些端口均由半导体MW发生器连接和控制。原型3点MDI在单缸性能发动机和量产多缸发动机中均经过测试。在部分负荷和低负荷，低发动机转速的目标条件下，在两台发动机中，多点MDI的性能都比单个MDI和传统的火花塞好得多。在性能引擎中，三点MDI导致燃烧时间最短，尤其是在早期阶段。但是，当以两个活动的MDI端口作为插头运行时，三点MDI会超过生产引擎的稀薄运行能力，因此，三点MDI的全部潜力目前已超过当前生产引擎的水平。