Abstract
Cyclic instability is a common problem in the operation of conventional two-stroke spark-ignition engines. Previous research has shown that auto-ignition (AI) could help solve this problem. However, at light engine loads, even under AI, the cyclic instability may still be significant due to the difficulty in maintaining the minimum temperature required by AI. Despite the benefits brought by AI in fuel consumption and emission reduction, the high level of cycle-to-cycle variation at light load may delay the realization of AI operation in engine products. To solve this problem, spark assistance has been identified as a cost effective and convenient way to improve the stability of AI operation at light load. This paper aims to report our experimental investigation to the effectiveness of spark assistance on cyclic variation of AI at light engine load conditions.