Compressed air to replace internal combustion?

There's always a marketplace for new ideas, and one seems to offer the shangri-la of automobile design--pollutant and fossil-fuel free. As always, there's a hitch:

Moteur Developpment International, is developing a line of cars, vans and pickups powered exclusively by compressed air. There's no gasoline, no costly service schedules and no polluting exhaust.

The prototype vehicles are so clean, the company says, that the air coming out of them is often cleaner than when it goes in.

"This represents something truly revolutionary in the automobile industry," said Shiva Vencat, the company's representative in the United States. "We are talking about changing the way we make cars, how we buy cars, and, more importantly, we are talking about a clean car."

MDI claims that its air-powered automobiles will eventually render the internal combustion engine "as obsolete as the black-and-white television."

The company plans to produce vans, family sedans, taxis, small trucks and three-passenger runabouts called the MiniCat.

All are prototypes. Their bodies are made of aluminum tubing, fiberglass and injected foam. Prices are expected to range from less than $10,000 for the MiniCat to $16,000 for a six-seat sedan called the CitiCat.

These are no ordinary cars. Power comes from fresh air stored in reinforced carbon-fiber tanks beneath the chassis. Air is compressed to 4,500 pounds per square inch — about 150 times the pressure of the typical car tire. The air is fed into four cylinders where it expands, driving specially designed pistons. About 25 horsepower is generated.

Though technical problems are being worked out, company officials say the car is capable of 70 mph and a 120-mile range under normal city conditions, performance that is comparable to electric cars.

Critics say the car has had trouble living up to its range projections. But company officials say they are trying to overcome that by warming the stored air.

Recharging the onboard tanks takes about four hours using the car's small compressor, which can be plugged into any wall outlet. Gas stations equipped with special air pumps can replenish the tanks in about three minutes. Company officials say the oil only needs to be changed every 31,000 miles.