CVCC-II
The 1983 Honda Prelude (the first year of the second generation of Preludes) used a CVCC design and a catalytic converter to reduce emissions, called CVCC-II, along with 2 separate sidedraught carburettors (instead of a single progressive twin choke carburettor). The following year a standard cylinder head design was used and the centre carburettor (providing the rich mixture) was dropped. The Honda City AA, introduced in November 1981, also used a CVCC-II engine called the ER.
Read more about this topic: CVCC