The feasibility of the Sonex. Combustion System (SCS) has been investigated for alcohol use in a single-cylinder, naturally aspirated DI engine. The SCS concept is to utilize active chemical species mated in specially designed small cavities in the piston bowl to enhance pre-ignition chemical reactions. With a prototype SCS piston, the CI engine ran stably from full load to 75% load on neat methanol and ethanol at a compression ratio of 17.5:1, without any ignition assist. At low load conditions, preheating of intake air was used. The idea of utilizing chemistry effects in the SCS design was proven to be feasible as a cetane-improving technology.