Honda CVCC "Compound Vortex Controlled Combustion" History

Honda CVCC “Compound Vortex Controlled Combustion” History

CVCC was trademarked by the Honda Motor Company for an engine with reduced automotive emissions, which stood for “Compound Vortex Controlled Combustion“. This technology allowed Honda’s cars to meet United States emission standards in the 1970s without a catalytic converter and to pass the 1975 standards of the Clean Air Act.

The name was a last minute decision amongst Honda Executives as they weren’t sure how to reveal the newly thought of design without giving away it’s features.
“Even though we had determined the possibility, we were still in the middle of research,” Date recalled. “In fact, we were still processing our patent application. This meant that the name of the engine had to be contrived carefully, in order that the public announcement not reveal even a part of its structure. And we were as yet undecided about how to supply fuel. We got our heads together to come up with a name that was unique; something that had a bit of punch to it.” Date, Yagi, and Nakagawa immediately convened in the reception room at Honda R&D Center, in order that they might come up with a name for Honda’s new engine. The official name they decided on just before the announcement was “CVCC”.

Soichiro Honda held a news conference on February 12, 1971, at the Federation of Economic Organizations Hall in Tokyo’s Ote-machi. There he announced, “We now have the prospect of developing a reciprocating engine that meets emission regulation standards for 1975. We will launch the commercial production of this engine in 1973.”

In 1972, a 100 Units were made at the Saitama Plant and placed in Nissan Sunny bodies for bench testing. The results started to showed up and it incredibly worked and lowered CO, NOx, and HC emissions. It soon become one of Honda’s crowning achievements in combustion engines for low emission vehicles. Picture above shows Soichiro Honda (founding father of the Honda Motor Company) at the debut of the CVCC engine to journalists around the world at Tokyo’s Akasaka Prince Hotel on October 11, 1972.

The Main Development Team
Kume, Zhi Shi (President and third generation later) responsible for the development:
Shoichiro Irimajiri
Nobuhiko Kawamoto (President and fourth generation later)
Osamu Goto
Yoshi Satoshi Sakurai

The engine design took the automotive world by storm, especially the US. The big three in the US shook their heads at the news and saw that even with specialized setup, it would be too costly and not allow the required horsepower that Americans needed for everyday use. Honda immediately proved the US auto manufacturers wrong by submitting three of their cars to the EPA for testing. Two had 15,000 miles on them, while one had completed a 50,000 mile durability test, which was conducted in the presence of Honda representatives during December 7—14, 1972. After the results, manufactures such as Toyota, Ford, Isuzu tried to get their hands on the technology. Toyota was successful and even signed an agreement with Honda for use of their technology. Soon all the above had signed agreements and Honda allowed tours of the new technology to almost anyone interested.

The EPA held a public hearing on March 19, 1973, in Washington, D.C., to hear the testimony of automakers on whether to implement the 1970 Clean Air Act as scheduled. At the hearing, the only automakers who testified that they could meet the 1975 regulations were Honda and Toyo Industries (now Mazda). “At the hearing,” recalled Date, “we were asked, ‘Can Honda really produce cars that meet the 1975 requirements? And if so, can Honda supply CVCC engines to automakers such as GM?’ But honestly, we had our hands full just taking care of Honda’s business. We didn’t have the capacity to supply products to a company the size of GM. It was a very frustrating experience.” The demands were simply too much for the industry as a whole. So, as a result of the hearing, it was decided that implementation of the Clean Air Act would be postponed.

Shipments of Civic/CVCC automobiles to the U.S. market began with the 1975 model year. Prior to exportation, however, the car had to be certified as satisfying the Clean Air Act. Even though the CVCC engine itself had passed the 1975 qualification test in 1972, it had not yet been tested as a complete vehicle so Honda had to be retested. “With the test completed and the computer spitting out numbers,” remembered Takeo Fukui, who was in charge of EPA certification, “I felt like I was waiting for the results of my college entrance exam.” “Congratulations!” said a cheering EPA inspector, offering his handshake when the test was completed. Mizoguchi and Fukui were certainly overjoyed just for having achieved certification, but the EPA inspector told them their product also got the top rating for fuel economy. “We were so preoccupied with emissions that we hadn’t given any thought to fuel economy,” Fukui said. “But to the EPA, passing the emissions test was no big issue. It was fuel economy that mattered. After all, they had the future in mind.”

The General Motors Experiment
Not much is known or recorded but it was noted back in the early 70’s that GM was stating to get irritated at the idea of Japanese Cars being sold in the US. Being one of the big three, GM relied on it’s big block V6’s & V8’s to give Americans the needs to conquer the American highways and didn’t rely too much on emissions. When word got out that Honda was testing to pass the 1975 EPA standards, GM snubbed at the idea and thought it would be a waste of time. After passing the tests, GM quickly turned their head and started to show interest in the technology. Honda approached the idea that their technology could improve even the standard American engine by implementing their heads on GM’s engine blocks. A 2.4l Chevy Vega was retrofitted with the CVCC heads and results showed an improvement across the board. Another test took place on a bigger sized engine, one more practical to Americans, the 350 CID from a Chevy Impala. Results came in again as an improvement across the board but GM turn their cheek as costs to retrofit the new technology would be costly. NSA reported that with simple retooling and some new parts, it would add the cost of $60 to each engine to meet the requirements

In October of 1973, GM sent to the EPA their report on the 350 CID CVCC experiment.
*Highly Recommended To Read* 1980 DOT (Department of Transportation) Report

So what’s the setup?

C (“Compound”) represented the engine mechanism with two combustion chambers: main and auxiliary. V (“Vortex”) represented the vortex, or swirl, generated in the main chamber. Caused by a jet of flame from the prechamber injected via a nozzle, the vortex had the effect of increasing the speed of engine combustion. CC (“Controlled Combustion”) represented the engine’s ability to properly control the speed of combustion.

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.


Honda’s big advancement with CVCC was that they were able to use carburetors and they did not rely on intake swirl. Previous versions of stratified charge engines needed costly fuel injection systems. Additionally, previous engines tried to increase the velocity and swirl of the intake charge in keeping the rich and lean mixtures separated. Honda was able to keep the charges adequately separated by combustion chamber shape. It first appeared on the 1975 ED1 engine (or codenamed “993”).