21 to the air flow cleaner upstream of valve 8 so that the pre chamber air does not first pass through valve 8 valve 21 is coupled to main chamber throttle valve 18 through suitable mechanical coupling means 17 it will be understood by those skilled in the art that coupling means 17 may include mechanical scheduling means as may be desired in any event throttle means 18 and 21 are actuated by the same throttle input as shown in the figure throttle valve 21 is coupled to a pre chamber intake manifold 25 which in turn is coupled to pre chambers 30 and 32 it will now be understood by those skilled in the art that with a multi point fuel injection arrangement as described a precise generation and distribution of a rich air fuel mixture is provided to pre combustion chambers 30 and 32 thus with the system as described in fig1 the capability of effectively burning a lean mixture is achieved by 34 spark igniting 34 a rich mixture in a small pre chamber and using the burning rich mixture to 34 torch ignite 34 a much larger volume of the lean mixture spark ignition is thereby supplemented with torch ignition allowing the combustion of the lean mixture at air fuel ratios far.