a throttle shaft and butterfly construction is formed by molding both components from composite plastic , the shaft having integral bosses which are received in holes formed in the throttle plate . the bosses are ultrasonically or heat staked to lock the throttle plate onto the throttle shaft . the butterfly has ribs extending across a face of the butterfly substantially to the edge of the valve in a direction parallel to the flow of air across the butterfly to stiffen the butterfly and reinforcing ribs on the butterfly parallel to the throttle shaft to stiffen both the butterfly and the throttle shaft .