The CVCC engine debuted in 1975. Offered alongside the standard Civic engine, the 53-horsepower CVCC engine displaced 1,488 cc and had a head design that promoted cleaner, more efficient combustion. The CVCC design eliminated a need for a catalytic converter or unleaded fuel to meet emissions standards. (Every other U.S. market car for this year underwent the change to exhaust catalysts and the requirement to use only unleaded fuel.) Due to California’s stricter emissions standards, only the Civic CVCC was available in that state.
A five-speed manual gearbox became available this year, as did a Civic station wagon (only with the CVCC engine). A CVCC engine has a special cylinder head. The CVCC head uses a stratified charge combustion chamber. A stratified combustion mixture is richer at the sparkplug and much leaner at the main part of the combustion chamber. The rich mixture is easily ignited by the sparkplug and this initial flame will ignite the remaining leaner mixture. The CVCC head uses a pre-combustion chamber that is about the size of a thimble. The CVCC carburetor is two carburetors in one, a lean part and a rich part.
The lean part feeds the main combustion chamber, and the rich part feeds the pre-combustion chamber. The rich mixture in the pre-combustion chamber is ignited. A “flame hole” in the pre-combustion chamber allows the pre-combustion flame to blow across the regular combustion chamber and ignite the lean mixture.
