2-Stroke Engines Stir New Interest From Carmakers

Though wary of new motors, carmakers lured by fuel-economy gains. BEATING A BAD RAP

A FLIGHT of fancy - or a glimpse into the future? The Neon is probably a bit of both. Unveiled at the Detroit Auto Show early this year, Chrysler Corporation's four-door is full of surprises. Despite its subcompact exterior, the Neon has nearly enough passenger space to be rated a compact, even a midsize.

``It is possible that by the mid-'90s, many families will choose sedans close to the size of today's subcompacts,'' says Tom Gale, Chrysler's head of design. But that doesn't mean they'll have to settle for anything nearly as cramped, Mr. Gale says.

To understand why, pop open the unusually small hood. Tucked neatly inside is a tiny engine, half the size of a conventional 1.2-liter power plant. The motor is anything but ordinary. It generates close to 100-horsepower, as much as many 1.8-liter engines. It also has barely half the moving parts of a standard car engine.

And, perhaps most important of all, ``Our prototype [engine] has achieved up to 40 percent more fuel-economy'' than a conventional engine, says Francois Castaing, head of Chrysler's engineering department.

That's because the Neon is powered by a revolutionary new design known as a 2-stroke.

True, the 2-stroke has been around in various forms since 1872. But until recently, it was an engine no automotive engineer could love.

Two-strokes are used on almost every gasoline-powered lawn-mower, and on outboard motorboats. They also powered the noisy, smoke-belching East German Trabant passenger cars.

Older 2-stroke designs earned their nickname, ``corn-poppers,'' because of the loud pop-pop-popping noise they'd make while idling. They also burned a lot of fuel and dumped up to 100 times more pollution into the air than the 4-stroke engines used in most passenger cars. That's because of a fundamental design flaw.

In a 4-stroke, valves precisely regulate the flow of air and fuel into the engine. The mixture is then compressed and ignited. After it is burned, exhaust valves open, and the piston compresses again to flush the cylinder clean.

In a 2-stroke, the piston uncovers both the intake and exhaust ports simultaneously, so the fuel/air mixture is injected into the cylinder at the same time the exhaust gases are flushed out. Without valves, some unburnt fuel spills out the exhaust.

To bring the 2-stroke in line with modern demands, automotive engineers at Chrysler and elsewhere are coming up with a variety of high-tech fixes.

One of the leaders in the race to develop a modern 2-stroke is the Orbital Engine Company, an Australian firm that a decade ago pioneered the effort to redeem the 2-stroke's reputation.

After 4,000 miles, a test car powered by a prototype Orbital 1.2-liter, 3-cylinder XK engine is generating incredibly impressive emissions numbers. If the numbers can hold in mass production, the engine will easily pass the new air-quality standards set by Congress last year. In fact, Orbital believes its latest prototype may be the only gasoline-powered engine now able to beat the tougher Ultra-Low Emission Vehicle standards set by California.

So why isn't every carmaker in the world rushing to market with a 2-stroke?

For one thing, ``everybody is scared about durability - that five or six years out they'll have to do a major recall,'' cautions Tom Wilkinson, Detroit editor for Motor magazine. The new Clean Air Act will require vehicles meet emissions standards for 10 years or 100,000 miles, or else be fixed, possibly at tremendous cost.

And automotive engineers have long memories.

``There is a lot of reluctance to retool,'' admits Ken Johnsen, chairman of Orbital's United States manufacturing subsidiary in Tecumseh, Mich. ``There is the fear of the unknown. Some companies lost a lot of money on the Wankel engine.''

Two decades ago, General Motors, American Motors, Mercedes-Benz, and others were rushing another ``revolutionary'' new engine, the Wankel rotary, into production. But they discovered a series of major problems at the last minute, and all but one manufacturer, Mazda, yanked the rotary from their line-up. Industry losses neared $1 billion.

Still, Mr. Johnsen, Mr. Wilkinson, and Chrysler's Castaing believe the 2-stroke is going to catch on - soon.

Today, virtually every carmaker in the world is working on a 2-stroke design - along with India's Bajaj, the world's third-largest motorcycle manufacturer, and a number of boat-engine makers.

Johnsen says Orbital plans to begin full-scale production in Tecumseh by late 1993. Orbital officials won't say who plans to buy the engines, but hint it would be one of their Big-Three licensees, either GM or Chrysler.

Orbital's long-term goal, however, is not to build engines but to license its technology - at $30 to $50 per engine. By some accounts, a successful 2-stroke might someday capture up to half the world automotive engine market. With 45 million cars and light trucks built in an average year, that's a lot of money.