An efficient, power-enhanced ignition system

Spark ignition engines typically have ignition systems that develop 20-30 kV for breakdown of the spark plug gap and deliver current pulses in the range of 30-100 mA. These systems are characterized by very low energy transfer efficiency, 1% or less. Most of the energy is dissipated by the resistances in the transformer, spark plug wires, and spark plugs. This operating mode is adequate (but not necessarily optimum) for most engines, but will not meet the needs of future lean burn and some alternate fuel engines that require higher energy discharges to effectively ignite air/fuel mixtures. Requirements for increased ignition power and energy will have to be met with higher efficiency ignition systems. Improved efficiency can be achieved by utilizing peaking capacitors in the secondary circuit, preferably with a low-loss spark coil. With these modifications, the transfer efficiency can be increased to the 50-75% range. This paper summarizes the results of high-power ignition experiments and related electrical system analyzes for so-called “breakdown ignition” conditions. It includes descriptions of conventional ignition systems, a method for upgrading, and a new higher energy system that features multiple drivers and an energy recovery circuit. The effects of power-enhanced ignition on mileage and emissions for a variety of vehicles tested in laboratory and on the road are summarized sufficiently to show a range of typical results. The paper does not include comprehensive test data for a wide range of vehicles and operating conditions