Archive for the ‘emissions’ tag
Cars of Futures Past – 1975 Honda Civic CVCC
1974 Honda Civic CVCC; the car debuted in the U.S. for 1975. Photos courtesy Honda North America.
In 1970, the U.S. Clean Air Act of 1963 was amended with the addition of the “Muskie Law,” which required automakers to reduce carbon monoxide, hydrocarbon and nitrogen oxide levels by 90 percent. compared to 1970 levels, in time for the 1975 and 1976 model years. While most automakers scrambled to revise existing engines to run with catalytic converters and unleaded gasoline, Honda took a radical approach to meeting these standards: It designed an entirely new stratified-charge engine, the CVCC (for Compound Vortex Controlled Combustion), then fitted it to a car that would determine its fate as an automaker.
To understand the significance of the CVCC design, it’s necessary to first take a trip back in time to the mid-1970s. Unleaded gas became widely available in 1974, and most cars that would debut in 1975 reduced emissions via the use of fragile, two-way catalytic converters. New cars would require the use of unleaded gasoline, which was formulated for use with emission control-equipped vehicles.
Pre-1975 vehicles could be run on leaded gasoline, or a low-lead formulation that helped protect the environment while still lubricating valves inside the engine. New cars were equipped with restrictive fuel inlets, and revised narrow gas pump nozzles were deployed on pumps dispensing unleaded gasoline; using leaded gas in a catalyst-equipped car would clog the elements of the device, necessitating costly repair. On the other hand, using unleaded fuel in a car designed to run on leaded fuel could result in internal damage, such as burned valves, as older engines were not designed to operate on the new fuel.
The Civic’s 1.5-liter CVCC engine.
The plan seemed simple enough until supply restrictions caused shortages of unleaded fuel, potentially leaving owners of new cars stranded. Among the benefits of Honda’s CVCC engine design was that it met Clean Air standards without the use of a catalytic converter, allowing Civic owners to use leaded, unleaded, or low-lead fuel without risk of engine damage. Not only was Honda ready for the changes to the automotive market in 1975, it had met the targets in testing as early as December of 1972.
Honda began working on its stratified charge CVCC engine design back in 1966, primarily as a way to separate the company from the rest of the automotive herd. Though the technology sounds complex, it’s really quite simple: Starting with a conventional, carburetor-equipped, four-stroke internal combustion engine, the CVCC design added a second, smaller inlet valve to a miniature precombustion chamber located near the spark plug.
When the valve opened, an enriched fuel/air mixture was drawn into the precombustion chamber, at nearly the same time a leaner fuel/air mixture was drawn into the conventional cylinder. When the spark plug ignited the rich mixture, this flame from the precombustion chamber, distributed through perforations in the chamber’s bottom, would ignite the lean mix, resulting in a more complete combustion with fewer noxious emissions. Though Honda did not invent the stratified-charge engine, it does earn the distinction of being the first automaker to use the design in a gasoline-fueled passenger car, and it incorporated a cost-effective two-stage carburetor instead of relying on more expensive fuel injection.
Though Honda’s 1.5-liter CVCC engine was EPA approved in December of 1972, the automaker didn’t debut the engine in the United States until the 1975 model year. The car that would benefit from this technology, the Civic, first appeared in 1973, equipped with a 1.17-liter four-cylinder engine of conventional design. This would be upgraded to a slightly larger 1.2-liter engine in 1974, giving the Civic an output of 52 horsepower.
Even before the CVCC engine debuted, Honda had placed a significant burden on the Civic; because earlier attempts at building passenger cars for export, such as the diminutive N600 and Z600, met little acceptance in a U.S. market largely unconcerned about fuel economy, the Civic would be the make-or-break vehicle for Honda as a global automaker.
When the 53-horsepower CVCC-equipped Civic hit the market in 1975, it debuted alongside the conventional (and less expensive) 1.2-liter four-cylinder engine. In an effort to convince a skeptical American public that Honda was serious about building practical and durable cars, the automaker ran six Civic CVCC models in a 72-hour endurance marathon at California’s Ontario Motor Speedway.
Over the course of the event, the cars accumulated 27,686 miles, all essentially flat out, while suffering just four minor mechanical maladies (a broken speedometer gear, a failed fuel pump, a blocked fuel line and a radiator coolant level issue). Even running at an average speed of 84.2 miles per hour, the Civics returned 20.16 miles per gallon when equipped with the five-speed manual transmission and 15.89 MPG when fitted with the two-speed Hondamatic automatic transmission.
Despite praise of the car’s handling in the automotive press (aided by its four-wheel independent suspension), the public soon began embracing the Civic for its roomy interior and stellar fuel economy. When driven under normal circumstances, the Civic CVCC returned an estimated 28 MPG in the city and 42 MPG on the highway. Perhaps the CVCC’s biggest selling point, however, was its multi-gasoline-grade capability; while owners of other cars were struggling to find unleaded fuel, Civic CVCC drivers could top off with whatever fuel was readily available.
History tells us that the Civic CVCC was a success, paving the way for Honda to become a well-respected, full-line automaker. Eventually, catalytic converters would be fitted to CVCC engines to further reduce emissions, and the efficient combustion of fuel injection would render the carbureted CVCC engine design obsolete. Still, it’s safe to say that without the Civic and, quite possibly, without the CVCC engine, today’s automotive landscape would look significantly different.
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