Unquestionably, the original Honda Civic is the car that put the Japanese automaker on the global map. Born from the failure of the company’s first proper mainstream car, the 1300, the Civic allowed Honda to leapfrog its domestic competitors on front-drive small cars and it was easily a match for global bestsellers like the Fiat 127 and Renault 5. But one of the cleverest aspects of the car, and one that doesn’t get all that much attention today, was the CVCC (Compound Vortex Controlled Combustion) cylinder head.
This clever solution allowed the Civic to meet new (and very strict for the time) emissions regs without a catalytic converter, without requiring unleaded gas, and without any real sacrifice in fuel economy or performance versus the non-CVCC original engines. This made the car materially better and more adaptable to various markets, and it was something the company was justifiably proud of.
Since we benefit now from almost 60 years of anti-pollution laws, it’s easy to forget that in the 1960s layers of brown smog were normal, day-to-day vistas from the top of tall buildings in big cities.
Severe smogs were also familiar events. In November of 1966, 168 deaths were tied to a three-day smog cloud that engulfed New York City over Thanksgiving, and it followed similar episodes in 1963 and 1953. Nor was New York unique. Similar episodes in London, L.A. and Tokyo, which was subject to a smog event so severe in December of 1964 that city lights were turned on during the day.
All this led to considerable concern on the part of ordinary citizens and led to the U.S. passing the Clean Air Act in 1963, with may addendums to follow. Other nations soon followed.
Honda engineers, led by engine research lead Shizuo Yagi, began studying pollution reduction as early as 1965 and despite management skepticism, set up an Anti-Pollution (AP) lab in 1966. That new lab followed a month-long visit to the United States, sponsored by the Japanese Automobile Manufacturers Association (JAMA), in which Yagi and engineers Tasku Date and Kazuo Nakagawa toured pollution and safety research facilities at Ford, GM and Chrysler.
The AP Lab’s task was to make sure that when Honda, already dominant in the motorcycle world, was ready to launch mass-market cars internationally, they’d be on even footing with more established companies in meeting new regulations.
Yagi, Date and a horde of other engineers studied all kinds of things, gas turbines, rotary engines, thermal reactors, Stirling engines and even alternative fuels like alcohol and hydrogen. But Soichiro Honda himself eventually encouraged them to focus only on conventional gas engines, because reinventing the combustion process was simply too great a task from a manufacturing standpoint.
The AP lab looked closely at catalysts and catalytic converters, which at that time were used mainly on stationary engines in factories. They weren’t an ideal solution, in particularly because scaling them down led to poor reliability, they were costly, they got very hot, and tuning the engine to make them maximally effective hindered performance.
Nor would adding a thermal reactor help. BMW, Mazda and several other manufacturers tried this in the mid-1970s as way to avoid the catalytic converter, but it properly destroyed fuel efficiency, and the thermal reactor generated lots of heat, which could cause other problems.
The only way to reduce emissions without sacrifices was to find a way to burn the fuel more completely. The AP lab tried many things including multi-spark heads, different mixtures and different chamber designs, but nothing worked until Date hit on the idea of a pre-chamber, an idea used by some diesel engines in Japan and, strangely, the Soviet Union. Here the idea was to pre-ignite a small amount of a very rich mixture which could then average with a very lean mixture in the combustion chamber, and that’s exactly how the CVCC works.
The system has normal inlet and exhaust valves, but also a tiny secondary inlet valve above a small secondary chamber adjacent to the main chamber and linked by a narrow passage. A very lean mixture enters the big combustion chamber via the regular valve, while a very rich mixture goes into the much smaller pre-chamber, which is then ignited by the plug. The rich mixture burns hot as it moves into the regular chamber, igniting the lean mix and resulting in a very clean burn.
Honda did not have water-cooled engines to test this idea out on, so early examples were tested in the air-cooled E2 engines from the N360/N600 and on Nissan engines the company bought on the down-low. The CVCC was not ready for prime time in early 1971 when Mr. Honda announced it to the public, but concern over air pollution was front-page news in Tokyo at the time and Honda grabbed headlines by showing that it was working on a potential solution.
Because the idea was fundamentally just a fancy cylinder head, it could easily be applied to a wide variety of engines, which led the company to quickly license the technology to most of its Japanese rivals and anybody else who wanted it. This led to an ill-advised public comment from GM President Richard Gerstenberg, who dismissively said the tech “Might work on a little motorcycle engine,” but that he saw no future for it at GM.
Mr. Honda himself, sometimes referred to as “the old man” by his staff, then had a 1973 Chevrolet Impala shipped to Japan and had CVCC heads made for it. The big Chevy was then sent to the EPA’s U.S. labs for testing. Sure enough, it met 1976’s emissions standards without a catalytic converter, a device GM was forced to use on most of its vehicles in 1975, the very same year the CVCC finally ended up in production Hondas.
That was a triumph, but the CVCC idea was only good for so long. It was a good solution by early 1970s standards, but the switch to unleaded gas and the spread of fuel injection eventually led to its obsolescence, as did ever-tighter emissions regulations. The CVCC was clean but no engine could escape having a catalytic converter in the U.S. by the mid-1980s and the “CVCC-II” versions got one in 1983.
Even so, CVCC-head engines were used into 1990 in some markets, and Honda did not stop innovating on cylinder head design. We spied this awesome ‘77 Civic CVCC at Carlisle back in May.
