Mazda's I-Stop Offers Big Fuel Savings--But U.S. Testing May Keep it Off the Market

Last Updated Jan 28, 2010 4:07 PM EST

Unless you count the Tribute, a close cousin of the Ford Escape Hybrid, Mazda does not offer a hybrid car. But according to North American CEO James O'Sullivan, who was in D.C. for the Washington Auto Show, the company is targeting major fuel-efficiency improvements in its internal-combustion engines. "We think we can get to 30 percent in the next few years," he said.

Ford, which has introduced efficient small-displacement Eco-Boost engines with turbocharging, has a similar goal.

According to O'Sullivan, "The internal-combustion engine will be around for a long, long time. We can stretch the envelope even further. Fuel economy is what consumers are looking for. In the near future, gasoline engines will return the economy of diesels, and diesels will get the same fuel economy as today's hybrids."

Reducing carbon dioxide emissions, which is now strongly regulated both in the U.S. and Europe, is also part of Mazda's plans. And if you're a customer in Japan or the EU countries, you can order your Mazda3 with I-Stop. It's on 33 percent of Japanese-market cars. The technology, which turns off the Mazda3's engine at stoplights, then quickly starts it again when the brake pedal lifts, is familiar from many hybrid cars. But Mazda appears to be the first manufacturer to make it widely available on a standard internal-combustion vehicle.

Robert Davis, a Mazda vice president for research development and quality, said that Mazda's system differs from previous auto-stop systems in that it does not use the starter or alternator for restarts. Mazda's system, attached to a direct-injection engine, stops the pistons in the right position, squirts fuel into a cylinder with the engine stopped, then ignites it to start the engine. The engine restarts and reaches idle in a third of a second.

Unfortunately, Davis says, the $600 to $800 optional system, which yields five to eight percent fuel economy gains in the Japanese cycle, is pretty much of a bust when tested by the EPA. "In EPA's city mode testing, with few stop-and-start cycles, I-Stop offers only a two-tenths of a percent improvement," Davis said. "But in cities like Washington or New York, drivers make a great many stops and starts--this isn't something I'd force on consumers in Iowa." If the EPA test stands, Mazda will find its useful technology a hard sell on the American market: $800 for two-tenths of a mile?

"We're going to begin detailed discussions with the regulatory agencies and the Alliance of Automobile Manufacturers aimed at getting a new test procedure for the urban environment," Davis said.

The EPA sounded interested, but failed to return a call about testing for I-Stop.