Carbon fiber reinforced carbon (CFRC) composites possess high specific strength, without loss of strength at high temperatures. The fiber architecture of these composites can be manipulated to yield tailored mechanical and thermal properties. Because of their light weight and the above attributes, these composites are attractive for pistons and other reciprocating parts in internal combustion engines. However, few tests have been performed to test these pistons for structural integrity and engine performance.Testing was undertaken to assess the basic suitability of this material for use in a spark-ignition engine. Of particular were basic mechanical function and combustion effects.With the CFRC piston cylinder, hydrocarbon emissions were higher, IMEP lower and the higher piston temperature induced detonation prematurely. The increase in hydrocarbon emissions was attributed to higher crevice volumes under hot operating conditions and fuel adsorption/desorption into the piston crown.