CVCC

CVCC is a trademark by the Honda Motor Company for a device used to reduce automotive emissions called Compound Vortex Combustion Chamber, and it allowed Honda's cars to meet the 1970's US Emission requirements without a catalytic converter. It is a form of Stratified charge engine.

Honda CVCC engines have normal inlet and exhaust valves, plus a small auxilary inlet valve which provides a relatively rich air / fuel mixture to a volume near the spark plug. The remaining air / fuel charge, drawn into the cylinder through the main inlet valve is leaner than normal. The volume near the spark plug is contained by a small perforated metal plate, upon ignition flame fronts emerge from the perforations and ignite the remainder of the air / fuel charge. The remaing engine cycle is as per a standard four stroke engine.

This mix of rich mixture near the spark plug, and lean mixture in the cylinder allowed stable running yet complete combustion of fuel, thus reducing CO (carbon monoxide) and hydrocarbon emissions.

Pronouncing "C.V.C.C" as a word gave the Honda Civic its name.