Computers work well in new cars to reduce air pollution, but what can be done with old ones, especially in Third World countries where old models predominate? In those lands, where often the only gasoline is leaded, catalytic converters are not practical.
A startup company in Maryland won a patent last month for a device that cleans car exhaust and reduces fuel consumption by harnessing a computerized sensor to an old-fashioned carburetor.
The system can continually adjust the air-fuel mixture, making it as lean as possible at any given instant.
The Lean Power Corp. of Silver Spring, Md., attaches a magnetic sensor that monitors the speed of the engine’s flywheel, which is where the starter motor attaches. The sensor looks not only at revolutions per minute (a measure of engine speed) but also at the flywheel’s smoothness of revolution (an indication of performance) and sends the appropriate signals to an air-control device attached to the carburetor.
“When combustion is smooth and uniform, the sensor tells our controller that the engine will tolerate a leaner mixture,” said Michael D. Leshner, the company’s vice president and senior scientist. “When it gets rough, it tells our controller it’s a little too lean.”
From a chemistry standpoint, air and gasoline mix best at a ratio of 14.7 parts air to 1 part gasoline. But power is maximized at 12 to 1, and cleanliness is maximized at 19 to 1.
The Lean Power system decides how rich the mixture needs to be by looking at fluctuations in the flywheel, which runs faster after a cylinder fires and slows down between firings. A four-cylinder engine fires twice in each revolution, and the engine runs between 600 and 6,000 revolutions per minute, which means measuring a cycle of acceleration and deceleration 100 times per second or less.
Measuring something that fast mechanically is hard, but Leshner said, “for modern electronics, that’s slow. It’s 100,000 times slower than your personal computer.”
The company has been concentrating on Mexico, where it hopes soon to announce a joint-venture partnership with a manufacturer.
