Cleaning up an engine’s act

The humble two-stroke gasoline engine has done yeoman work for well over a century. The noisy beasts, invented by Sir Dougald Clerk in 1876, are reliable, easy to maintain, and powerful for their size. But they have a dirty secret.

Traditionally they belch out a cocktail of hazardous emissions in a haze of blue smoke, powering chain saws, weed whackers, snowmobiles, scooters, outboard motors, and the like.

Earlier this month, the US Environmental Protection Agency (EPA) announced long-awaited tough new emissions rules on small engines (25 horsepower or less), many of which still use two-stroke engines, as opposed to cleaner four-stroke ones.

When fully implemented in the next few years, the new standards will reduce hydrocarbon and nitrogen oxide emissions by 35 percent, the EPA says. The agency estimates that by 2030 these reductions will result in significant health benefits, redu­cing hundreds of premature deaths and hundreds of thousands of workdays and schooldays lost because of pollution-related illnesses. That would translate into a cost savings of between $1.6 billion and $4.4 billion, the EPA says.

But even as the US takes action, a bigger battle against dirty two-stroke engines awaits in Asia, where the engines power most scooters and motorcycles, many of which are used as unlicensed taxis.

“One of these dirty three-wheel taxis in India or the Philippines produces the pollution of about 50 modern automobiles,” says Bryan Willson, a professor of mechanical engineering at Colorado State University in Fort Collins. “And you’ve got 50 to 100 million of these in Asia, so you’re looking at over 2.5 billion car-equivalents of pollution. So that’s a huge environmental impact.”

Asian governments are looking at a number of measures to cut pollution from two-stroke engines, including replacing them with four-stroke power plants similar to those found under the hood of nearly every automobile. But because these small vehicles provide vital transportation and jobs for millions of people in Asia, simply mandating that they be taken off the streets isn’t an option.

A five-year-old nonprofit company called Envirofit International (envirofit.org) is promoting a solution that combines one part technology and one part entrepreneurship. Envirofit wants owners of these smoky vehicles, sometimes called rickshaws or tuk-tuks, to retrofit them with a kit that converts them to direct in-cylinder fuel injection. That reduces carbon monoxide emissions 90 percent and nitrogen oxides 70 percent, says Ron Bills, chairman and CEO of Envirofit in Fort Collins, Colo.

The conversion kits cost about $200, a huge investment for taxi owners who may make only a few dollars per day. That’s why Envirofit is working with micro-lending groups to help drivers afford the conversion. It’s also helping to train local mechanics to install the converters, creating more income for local people.

The incentive to taxi drivers comes in the form of a big boost in gas mileage once the engines are converted, about 35 percent better. That’s because unburned oil and gasoline no longer escape through the engine’s exhaust as smoke, a longtime drawback of two-stroke engines. Drivers can save about $2.80 a day on fuel (currently about $3.75 a gallon in Manila), meaning the conversion pays for itself quickly, says Mr. Bills, whose résumé includes a time as president and CEO of Segway, the maker of the innovative standup electric scooters. The money that drivers don’t spend on gasoline “goes directly into the local economy instead of out the tailpipe of a motorcycle,” he says.

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