Abstract: A charge conditioner for an Otto cycle internal combustion engine supplies hot, oxygen-free exhaust gas to premixed intake fuel and air charge in sufficient quantity to heat the charge and completely vaporize the fuel, while improving engine volumetric efficiency by filling the cylinders with a mass of exhaust gases introduced downstream of the throttle. The flow of exhaust gas to the charge is maximum from idle to approximately cruise engine power output, and is then progressively decreased up to full engine output until flow is prevented at maximum engine power output. A supplemental fuel supply system optionally adds vaporized fuel to the charge by using the hot exhaust gas as a fuel carrier to the charge intake stream.