Mazda says the $800 optional system, which yields five to eight percent fuel economy gains on Japan's test cycle, is a bust when tested by the EPA. It's for this reason alone that Mazda will deliberately delay the U.S. introduction of i-Stop. There is good news, though. Mazda says the technology will eventually make its way into vehicles sold here in the States, but not anytime soon. Look for i-Stop to slowly expose itself in the automaker's U.S. vehicles in 2016, says Jim O'Sullivan, chief executive officer of Mazda North America.
When attached to a direct-injection engine, the i-Stop system stops the pistons in a specific position when the car comes to a halt. Then, when the driver is ready to do, the system squirts fuel into a cylinder and ignites it to re-fire the engine. The engine restarts and returns to idle in one-third of a second.