Abstract: An exhaust manifold for an engine has sets of branches tuned to the fundamental frequency of exhaust products but with the branch length of the sets different so that the engine speed at which resonance occurs in each set is different. An inlet manifold has runner sets with each set being paired with an exhaust manifold branch set serving the same cylinders and tuned to effect resonance of combustion air in the runners at the same engine speed that resonance occurs in its associated exhaust branches.

Abstract: An intake manifold for internal combustion engines has a plurality of independent runners emanating from a central plenum. Different sets of runners have different cross-sectional areas matched to flow velocity through the manifold at maximum torque and desired engine speeds to produce a wide high torque band. The length of each runner of each set corresponds to a harmonic frequency of the fundamental frequency of air at standard temperature, but the frequency differs for each runner set. Within each set, runner cross-sectional areas are constant throughout their length. In one embodiment, the runners curve from a plenum to their exits and in the curve each runner's cross section is regular trapezoidal with the small side of the trapezoid on the inside curve and the shape of the trapezoid effecting constant static pressure throughout the cross section.

Abstract: The plenum of an independent runner manifold is oriented at an angle to the longitudinal center line of the manifold such that each carburetor throat of a four barrel carburetor sees the entire entrance of two adjacent runners of different runner pairs. Each of four runner pairs has two runners leading from the plenum to side-by-side inlet ports. The wall lengths within a runner are made at least nearly equal to each other. A sudden enlargement, in the form of a step, is provided proximate the entrance of each runner of a manifold to the ports of an engine along the outer wall thereof where mixture velocity is relatively low with respect to mixture velocity elsewhere in the same velocity profile. The enlargements control reverse mixture flow and increase the amount of mixture entering the engine's cylinders. It is believed that this increase in flow is partially due to a reduction or elimination of boundary layer separation in the inlet port.

Abstract: A plurality of steps in each runner of a manifold from the exit of the runners towards a plenum of the manifold are located where mixture velocity is relatively low with respect to mixture velocity elsewhere in the runner in the same velocity profile. The steps control reverse mixture flow and increase the amount of mixture entering the engine's cylinders.