CVCC - Compound Vortex Controlled Combustion

A CVCC engine is equipped with a special cylinder head. The CVCC head uses a stratified charge combustion chamber. A stratified combustion mixture will be richer at the sparkplug and much leaner in 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 result is a engine that will run on a much leaner mixture than was possible before.

The Honda CVCC head uses a pre-combustion chamber that is about the size of a thimble. The CVCC carb is actually two carbs built into 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 by a conventional sparkplug. 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.

An engine utilizing a CVCC head can run on much leaner mixtures than a conventional head can. Hondas use of the CVCC head allowed them to run without catalytic converters until the early 80s. Most of the other manufacturers went to a catalytic converter in 1975. The development of the CVCC head is a classic example of how Honda tries to control engine emissions by superior engine design.

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