fuel mixture and forcing it into the combustion chamber 82 through the intake exhaust opening 94 as seen in fig7 the spark plugs 90 and 92 are then energized to ignite the air fuel charge as seen in fig8 and the combustion products flow into the cylinder bore 66 to drive the piston 68 downwardly to effect an expansion stroke of the engine 60 as discussed above the intake compression and ignition events preferably are controlled to initiate and complete the combustion process as quickly as reasonably possible preferably within 20 u00b0 to 30 u00b0 ca to provide sufficient time for the supplemental air to be added to and effectively mixed with fuel rich products of combustion as discussed above rapid combustion or u201c fast burn u201d can be facilitated by using multiple spark plugs as illustrated and or by carefully designing the combustion chamber shape to maximize access of the air fuel mixture to the energy supplied by the spark plug s or other ignition sources during an early cycle secondary air injection event supplemental air is injected through the orifices 104 and into the air curtain during a secondary air injection event commencing after ignition of the primary combustion event where it penetrates the stream of hot combustion products flowing into the bore 66 from the combustion chamber 82 as.