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A key element to achieving vehicle emission certification for most light-duty vehicles using spark-ignition engine technology is prompt catalyst warming. Emission mitigation largely does not occur while the catalyst is below its “light-off temperature”, which takes a certain time to achieve when the engine starts from a cold condition. If the catalyst takes too long to light-off, the vehicle could fail its emission certification; it is necessary to minimize the catalyst warm up period to mitigate emissions as quickly as possible. One technique used to minimize catalyst warm up is to calibrate the engine in such a way that it delivers high temperature exhaust. At idle or low speed/low-load conditions, this can be done by retarding spark timing with a corresponding increase in fuel flow rate and / or leaning the mixture. Both approaches, however, encounter limits as combustion stability degrades and / or nitrogen oxide emissions rise excessively.

Conventional spark plugs ignite a fuel-air mixture via an electric-to-plasma energy transfer; the effectiveness of which can be described by an electric-to-plasma energy efficiency. Although conventional spark plug electric-to-plasma efficiencies have historically been viewed as adequate, it might be wondered how an increase in such an efficiency might translate (if at all) to improvements in the flame initiation period and eventual engine performance of a spark-ignition engine. A modification can be made to the spark plug that places a peaking capacitor in the path of the electrical current; upon coil energizing, the stored energy in the peaking capacitor substantially increases the energy delivered by the spark. A previous study has observed an improvement in the electric-to-plasma energy efficiency to around 50%, whereas the same study observed conventional spark plug electric-to-plasma energy efficiency to remain around 1%.

Measurement and analysis of typical automotive spark ignitions operating up to 30Kv and 30 to 100ma show the electrical-to-plasma (energy) transfer efficiency to be very low, significantly less than one-percent (1%).1 The reason for this low energy transfer efficiency is high resistance in the driving circuit that is in series with the rather low resistance of the ignition spark. The largest components of resistance are in the ignition coil and the high voltage cables. The latest evolution of ignition systems has been the elimination or severe shortening of the high voltage cable and the incorporation of one ignition coil attached directly to the individual spark plug. While this has eliminated much, and in some cases all, of the transfer losses attributed to the cables, the system as a whole is still very inefficient in the electrical-to-plasma conversion efficiency because the spark coil and spark plugs still have many times the resistance of the spark discharge channel.