Evaluation of critical ignition coil parameters for an application On naturally aspirated gasoline engines

Today’s internal combustion engines require highly efficient combustion systems to meet stricter emission and fuel economy regulations. To fulfil to these requirements the ignition system of a gasoline engine plays a critical role. Along with ensuring that it meets the ignition characteristics across all engine operating conditions, it is also possess challenges like to comply with certain On-Board Diagnostics (OBD) norms .To meet these demands modern gasoline engines use inductive type ignition coils which are directly installed at the cylinder head above the spark plug. These ignition coils generate high voltage to produce a certain amount of spark energy and primary coil current which are necessary to meet the targets. However, it has been observed that in a traditional inductive type ignition coil system the ignition coil operating temperature can be a major limiting factor as it cannot exceed a maximum upper limit. The work described in this paper details the various systematic evaluation studies and techniques carried out on an inductive type ignition coil system of a three-cylinder naturally aspirated gasoline engine. Various iterations like the effect of the battery voltage, dwell time, and engine speed on the ignition coil operating temperature have been studied and presented in detail with a systematic approach. The study also includes the effect of ignition coil operating temperature on a primary coil current. The authors have explained in detail the various test conditions and techniques used to understand these effects in the real-world operating environment. A result presented here led to the definition of optimized ignition coil parameters for a naturally aspirated gasoline engine to meet targeted engine performance including On-Board Diagnostics (OBD) requirement.