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Earth Sense: Carburetors fading as fuel injection offers cleaner air
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The carburetor is a time-honored device that may yet see its 150th birthday. But it’s disappearing almost completely from the automotive scene.

You’ll still find it on small engines like lawn mowers or chain saws. Its successor, fuel injection, requires sensors and electronics that would make the portable engines very complex.

Carburetors have been a major target of environmental agencies like the California Air Resources Board (ironically abbreviated CARB).

Every combustion engine needs a fuel delivery system that produces an exact mixture of air and gasoline vapor. Early Italian attempts during the late 1800s consisted of rotating brushes in a bowl of gasoline, in hopes the spray from the brush would get sucked into the engine in the right amounts. One can only begin to imagine the clouds of smoke that must have trailed the early automobiles.

When an engine got too much fuel, it flooded and became very hard to restart. In 1896, the fathers of the Daimler-Benz corporation invented a float system that would open and shut the fuel supply, reducing the number of vehicles stalled on the roadside.

Modern carburetors use an intricate network of passages, jets and valves to supply proper mixture at any speed. Today’s drivers demand precise “throttle response,” which was just a dream in the early 1900s, when a car had just two modes: “go” and “don’t go.”

Unfortunately, the amount of air available for carburetion changes with altitude. All but the most sophisticated carburetors have problems on trips from low altitudes to high mountain roads, and vice versa. A mile above sea level, which the Blue Ridge Parkway reaches many times, the air is thin enough to make carburetors run “rich.”

Too little air and too much fuel result in power loss and excessive air pollution with unburned fuel. Conversely, carburetors set for mountain driving would make the vehicle stutter and stall on seaside visits to Savannah. Dust in the carburetor could get the float stuck open, resulting again in flooding.

A friend of mine found one morning that the carburetor on his vintage motorcycle had leaked the entire content of the fuel tank, producing a dangerous lake of gasoline in the garage.

Now, electronic fuel injection monitors our engines, mixing the fumes precisely as they are needed, with a minimum of pollution. It can come with new problems, but a major benefit has been cleaner air.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. 

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