Mazda has developed its own start-stop system capable of turning its cars’ engines off while they’re stationary, then quickly restarting them when it’s time to pull away. The Mazda system differs from that of rivals in that it leaves the pistons in a pre-combustion position, injecting fuel and igniting it to restart the engine rather than using the electric starter motor. This makes it both faster (.35 seconds to start) and smoother. Mazda claims that, in urban areas where frequent stops are made in traffic — such as at stoplights — the system returns a 10% increase in fuel economy. But there’s a catch. The Smart Idle Stop System (SISS) only works with automatic transmission-equipped vehicles. This means that you’ll likely still be able to achieve overall better economy away from the city in an equivalent manual transmission vehicle. Nor is Mazda clear about when we’ll get SISSified vehicles, assuming they're coming to the US at all, or about which models will be so-equipped. The full press release follows:
Mazda Motor Corporation has independently developed an idling stop system, called the Smart Idle Stop System (SISS), which improves fuel economy by about ten percent (in Japan's 10-15 mode tests*1) in urban areas where vehicles frequently stop at traffic lights or in heavy traffic during operation. The SISS uses direct injection technology to achieve an excellent engine restart, ensuring drivers do not experience any discomfort with the new system. Mazda plans to introduce this core environmental technology to the marketplace in 2009. Idling stop systems save fuel by shutting down the engine automatically when the car is stationary, and restarts it when the driver resumes driving. Conventional idling stop systems restart a vehicle's engine with an electric motor using exactly the same process as when the engine is started normally. Mazda's SISS, on the other hand, restarts the engine through combustion. Mazda's system initiates engine restart by injecting fuel directly into the cylinder while the engine is stopped, and igniting it to generate downward piston force. In order to restart the engine by combustion, the pistons must be stopped at exactly the correct position to create the right balance of air volume in each cylinder. The Smart Idle Stop System provides precise control over the piston positions during engine shutdown to accomplish this. The SISS indexes each cylinder and initiates fuel injection before the engine begins to rotate. This enables the engine to be restarted in just 0.35 seconds*2, roughly half the time of a conventional electric motor idling stop system. In addition to saving fuel, Mazda's Smart Idle Stop System ensures that the engine will restart quickly and with exactly the same timing every time. Drivers will feel no delay when resuming their drive, which means they can enjoy a comfortable and stress-free ride. *1 The 10-15 mode test is the Japanese standard for emission certification and fuel economy for light duty vehicles. It consists of two separate drive cycles. The 10-mode drive cycle is a low speed drive cycle test, while the 15-mode is a higher speed assessment. *2 For vehicles with automatic transmissions. Restart times measured by Mazda.