Abstract: A charge forming system including an intake manifold having first passage means communicating with one-half of the engine combustion chambers; second passage means communicating with the other half of the engine combustion chambers; an air metering mechanism having passage means for respectively supplying a combustible fuel/air mixture or metered air to the first and second manifold passage means; and a control device disposed between the air metering mechanism and the intake manifold for controlling flow to the first manifold passage whereby the engine may operate on the power from one-half of its cylinders under low engine load conditions.