The surface of the combustion chamber is intended to absorb electromagnetic radiation from the flame at frequencies that coincide with the resonant absorption frequencies of the fuel. This prevents resonant energy transfer to the fuel, avoiding or suppressing formation of undesired radicals.The surface consists of two layers, one absorbing layer on the top and one second layer functioning as a transient heat buffer.The following advantages have been observed: Reduced octane number requirement of the engine. The ORI (Octane Requirement Increase) does not increase after the running, due to less deposits. Increased performance with low octane fuels through advanced ignition timing. The limit for run-away knock occurs later at high load. Lower HC emissions.