A gas-economizing powerful engine speed increaser is made integral, and positioned fixedly in an air intake tube connected with the front end of an air intake manifold of an engine. The engine speed increaser consists of an outer circular tube, an inner circular tube of a shorter diameter than that of the outer tube and positioned in the center of the outer tube, and a plurality of twisted leaves positioned spaced apart equidistantly between the outer tube and the inner tube. Air sucked in an air intake tube by the engine started and under operation flows through the engine speed increaser to become swirl wind by the twisted leaves and partly straight wind flowing swiftly through the center hollow of the inner tube and then enter the combustion room of the engine.