wide end that is at the gap 100 and approximately 15 u00b0 at its narrow end that is at its exit 106 thus during the early or initial opening of the valve 26 the only real route that the incoming air fuel mixture can travel is in the direction of the spark plug 104 whereas fig2 and 4 show the valve 26 closed fig3 and 5 depict the valve partially open so that the incoming air fuel charge is constrained to flow toward the spark plug 104 and not in a general direction or throughout 360 u00b0 more specifically the air fuel mixture is constrained to flow through an angle subtending approximating 20 u00b0 however after the valve head 28 moves downwardly beyond the lower edge of the generally cylindrical shroud 98 then the incoming air fuel charge is dispersed throughout virtually an entire 360 u00b0 or complete circle in other words it is only during the initial and limited opening of the valve 26 that stratification occurs and it is during this period that the stratified charge is directed toward the spark plug 104 it is not believed necessary to show an opening of the valve 26 beyond that.