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Continuously Variable Cam Phasers (CVCP) controlling both the exhaust and intake camshaft phasing in combination with air assist direct fuel injection and a wide variable spark gap is utilized to reduce the fuel consumption for a 4-valve Turbo Charged (TC) Spark Ignition (SI) engine. The spark plug and the air-assisted direct fuel injector are integrated into one unit in order to facilitate packaging in a modern 4-valve combustion chamber. This integrated component is referred to as the Spark Plug Injector (SPI). CVCP's are used to reduce pumping work by diluting the charge with large amounts of residual exhaust gas. This strategy, along with stoichiometric homogeneous operation enables the use of a Three Way Catalyst (TWC), considered to be a prerequisite to meet the emission standards of Ultra Low Emission Vehicles (ULEV) II and beyond. The ignition quality deteriorates with increasing levels of residual exhaust gas dilution.

This paper presents a study of the Spark To Piston (STP) concept, engaged in a modern Spark Ignition (SI) 4-valve per cylinder four stroke engine. The combustion stabilization effect from this concept has been utilized in order to increase the engine tolerance to dilution of the fresh air-fuel mixture. It is shown that this tolerance is significantly improved by the STP concept, especially if combined with a high-energy ignition system. Inherent with this improved tolerance comes the ability to reduce fuel consumption and emissions of NOx in a considerable amount. Consequently, STP must therefore be considered a competitive future technique despite its non-conventional approach.