Mazda's innovative i-stop engine-idling-stop system has won yet another award, this time at the lchimura Industrial Awards. While idling stop systems are now becoming commonplace due to the approximate 10% fuel savings they offer, conventional engine stop systems rely on a motor to restart the engine, whereas 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. Mazda's use of principles unique to the direct injection spark ignition (DISI) engine restarts the engine in just 0.35 seconds, about half the time of most other competing systems, while minimizing noise and vibration and drain on the batteries.

The awards, held by the New Technology Development Foundation of Tokyo are given annually to researchers or groups that make a significant contribution to industry by developing exceptional industrial technology in Japan.

Since i-stop was launched in Japan in the all-new Mazda3 (Mazda Axela in Japan) in June 2009, it has won a swathe of awards including the 2010 RJC Technology of the Year prize from the Automotive Researchers’ & Journalists’ Conference of Japan, the 2009 Eco-Products Award from Japan’s Ministry of Land, Infrastructure, Transport and Tourism (MLIT), the 2009 Technology Award from the Combustion Society of Japan, and the Technological Development Award from the Society of Automotive Engineers of Japan (JSAE).

Idling stop systems are relatively low cost and can be widely deployed to become a highly effective method of reducing CO2 emissions. In this sense, i-stop has great potential to contribute to a more eco-friendly world. Mazda’s i-stop leverages the characteristics of direct injection engines to achieve a "combustion restart." This means that when the engine is stopped, the i-stop system injects fuel directly into a cylinder, and then ignites it to generate downward piston force to initiate engine restart.

To restart an engine the i-stop way, the compression-stroke and expansion-stroke pistons need to be stopped at the correct positions to create the right balance of air volumes during engine shutdown. Of all the pistons stopped at the optimum positions, the system identifies the initial cylinder for fuel injection and ignites, to restart the engine. Even at extremely low rpm, cylinders are sequentially identified for ignition, making the engine quickly pick up idle speed.

These technologies enable the system to restart the engine with exactly the same timing every time, to enhance fuel efficiency and deliver smooth and comfortable acceleration for the driver at restart. The restart takes place in a mere 0.35 seconds (internal measurement on A/T vehicle), which is about 1/2 of the restart time taken by the conventional starter motor idling stop system.