CVCC

CVCC, or Compound Vortex Controlled Combustion , is an internal combustion engine technology developed and trademarked by the Honda Motor Company.
Etymology.
The technology's name refers to its features as such:
History.
Following the establishment of an "Air Pollution Research Group" by Honda in 1965, its collection of emissions data from American automakers, and subsequent research into emissions control and prechambers, the first mention of CVCC technology was by Soichiro Honda on February 12, 1971, at the Federation of Economic Organizations Hall in Otemachi, Chiyoda-ku, Tokyo.
On the advice of University of Tokyo professor Tsuyoshi Asanuma, then-Honda R&D Director Tasuku Date, Engine-performance Research Block head Shizuo Yagi, and then-Engineering Design Chief Engineer Kazuo Nakagawa began research into lean combustion. After Date suggested the use of a prechamber, which some diesel engines utilized, the first engine to be installed with the CVCC approach for testing was a single-cylinder, 300 cc version of Honda's EA engine installed in a modified Honda N600 hatchback in January 1970. This technology allowed Honda's cars to meet Japanese and American emissions standards in the 1970s without the need for a catalytic converter.
A type of stratified charge technology, it was publicized on October 11, 1972 and licensed to Toyota (as TTC-V), Ford, Chrysler, and Isuzu before making its production debut in the 1975 "ED1" engine. As emission laws advanced and required more stringent admissible levels, CVCC was abandoned in favour of PGM-FI (Programmed Fuel Injection) on all Honda vehicles. Some Honda vehicles in Japan used electronically controlled "PGM-Carb" carburetors on transitional Honda D, E and ZC engines.
In 2007, the Honda CVCC technology was added to Japan's Mechanical Engineering Heritage list.
Operation.
Honda CVCC engines have normal inlet and exhaust valves, plus a small auxiliary 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 remaining engine cycle is as per a standard four-stroke engine.
This combination of a rich mixture near the spark plug, and a lean mixture in the cylinder allowed stable running, yet complete combustion of fuel, thus reducing CO (carbon monoxide) and hydrocarbon emissions. This method 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 later to further improve emission reduction.
Advantages.
The most significant advantage with CVCC was that it allowed for carbureted engines that did not rely on intake swirl. Previous stratified charge engines needed costly fuel injection systems. Additionally, previous engines tried to increase the velocity and swirl of the intake charge to keep rich and lean mixtures separated; Honda was able to maintain separation via the shape of the combustion chamber.
The design of CVCC also allowed it to be adapted to existing engines, since only the cylinder head needed to be modified.
Early design flaw.
Some early CVCC engines had problems with the auxiliary valves' retaining collars vibrating loose. Once unscrewed, oil would leak from the valvetrain into the prechamber, causing a sudden loss of power and large amounts of smoke to flow from the exhaust pipe. These symptoms usually indicated the failure of critical oil seals in the motor that would result in costly repairs. However, the solution was quite simple; Honda corrected the problem with metal retaining rings that slipped over the valves' retaining collars and prevented them from backing out of their threads.
CVCC-II.
The 1983 Honda Prelude (the first year of the second generation of Preludes) used CVCC in combination with a catalytic converter to reduce emissions, along with two separate sidedraft carburetors (instead of a single, progressive twin-choke carburetor). This new system was called CVCC-II. The following year, a standard cylinder head design was used, and the center carburetor (providing the rich mixture) was removed. The Honda City AA, introduced in November 1981, also used a CVCC-II engine called the ER. Its use of CVCC was also known as COMBAX (COMpact Blazing-combustion AXiom).