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 operational feel that is barely noticeable. The system improves fuel economy by approximately eight percent (under Japan's JC08 mode test cycle.).
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 identified for sequential 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 economy, 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.
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 is required.
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 vehicles with automatic transmission) and its operation is barely noticeable.
i-stop offers a quick engine restart and a natural operation with little vibration and noise.