Editing CVCC (section)

== Operation ==
Honda CVCC [[Internal combustion engine|engines]] have normal inlet and exhaust valves, plus a small auxiliary inlet valve. On the intake stroke a large amount of a very lean mixture is drawn into the main combustion chamber; at the same time a very small amount of rich mixture is pulled into the pre-chamber near the [[spark plug]]. The pre-chamber near the spark plug is contained by a small perforated metal plate. At the end of the compression stroke, the pre-chamber is rich in fuel, there is a moderately rich mixture in the main chamber near the pre-chamber outlet and the rest of the main chamber is quite lean.  On ignition, flame fronts emerge from the perforations and ignite the remainder of the air–fuel charge. When the sparkplug in the pre-chamber fires, the rich mixture ignites easily and the flame spreads from there into the main chamber, igniting a mixture so lean it wouldn't have fired satisfactorily with just a sparkplug. The remaining engine cycle is as per a standard [[four-stroke engine]].

Formation of [[carbon monoxide]] and [[hydrocarbon]]s are minimized by the overall leanness of the mixture, and the stable and slow burning in the main combustion chamber keeps peak temperature low enough to suppress formation of oxides of nitrogen while keeping the mean temperature high enough long enough to give low hydrocarbon emissions. The design allowed the engine to burn less fuel more efficiently without the use of an [[exhaust gas recirculation]] valve or a catalytic converter, although those methods were installed subsequently to further improve emission reduction.