Abstract: An engine performance enhancing apparatus comprises a plurality of disklike copper pieces arranged latticewise and sandwiched between two sheets or cloths, sheets of copper mesh superposed, one each on the opposite outer surface of the sheets or cloths, and aluminum sheets superposed and fastened on the opposite outer surfaces of the copper mesh.This apparatus, on being simply disposed near an engine, brings about a beneficial effect of enhancing the output of the engine and, at the same time, decreasing the content of noxious substances in the exhaust gas, reducing the black smoke emanating from a diesel engine, and improving the rate of fuel consumption.