Idling stop systems save fuel by automatically shutting down the engine when the vehicle is static, and restarting it when the vehicle returns to motion.
Mazda's "i-stop" substantially improves fuel economy while maintaining a natural driving feel. The latest control technologies achieve a rapid engine restart and an operation feel that is barely noticeable. The system improves fuel economy by approximately eight percent (under Japan's JC08 mode test cycle).
- i-stop with Gasoline Engines
Idling stop systems save fuel by automatically shutting down the engine when the vehicle is static, and restarting it when the vehicle returns to motion. While conventional idling stop systems rely on a starter motor to restart the engine, Mazda's i-stop restarts the engine through combustion: fuel is directly injected into a cylinder while the engine is stopped and ignited to generate downward piston force. The result is a quick and quiet engine re-start compared to other systems, and a significant saving in fuel.
To restart the engine by combustion, the compression-stroke and expansion-stroke pistons need to be stopped at exactly the correct positions to create the right balance of air volumes. Mazda's i-stop ensures precise control over the piston positions during engine shutdown. With all the pistons stopped at the optimum positions, the system then identifies the initial cylinder for fuel injection. It injects fuel and ignites it to restart the engine. Even at extremely low rpm, cylinders are sequentially identified for ignition, making the engine quickly pick up to idling speed.
These technologies enable the system to restart the engine with exactly the same timing every time, to enhance fuel efficiency, and to deliver smooth and comfortable acceleration for the driver at restart. The restart takes place in a mere 0.35 seconds (internal measurement on vehicle with automatic transmission), which is about half of the time taken by conventional starter-motor idling stop systems.
- i-stop with Clean Diesel Engines
Unlike gasoline engines, which use a spark plug to ignite the air-fuel mixture, diesel engines compress the mixture until it spontaneously combusts. Therefore, to restart a diesel engine, sufficient compression must be generated. While conventional diesel engine idling stop systems require two engine cycles to restart, Mazda's unique "i-stop" needs just one cycle, thanks to its precise control of the piston positions. As a result, "i-stop" achieves the world's fastest diesel engine restart time of approximately 0.40 seconds (internal measurement on vehicle with automatic transmission) and a barely noticeable operation.
