Spark Plug as an Ionization Sensor in Engine Knock Detection
Wu Xiaomin, Li Fuming, Jiang Deming, Wang Ziyan
(Xi'an Jiaotong University, Xi'an 710049, China)

Abstract: A method is presented for monitoring knock in automobile engine. It uses a spark plug as an ionization sensor. By applying bias voltage across the spark plug, ionic current takes place. Knock is detected when ionic current prevails with different frequency. Experiments are done on a four-cylinder type DA462-A. Test results show that engine with knock or without knock produces high frequency ionic signal or smooth signal respectively. Fast Fourier transform is used to analyze the data. The characteristic frequency domain (10~11kHz) of engine knock is obtained. The use of spark plug as an ionization sensor is an efficient and convenient method for the knock measurement of SI engine.
Keywords: spark plug;ionic current; knock