Mazda’s Smart Idle Stop System uses Direct Injection Engine Technology
By Jack Martin
September 8, 2008
September 9, 2008 The imperatives of better fuel economy and reduced emissions are breeding some fascinating developments of the good ol’ Internal Combustion Engine (ICE). One of the most logical ideas could have been invented by any schoolboy – turn off the engine when it isn’t being used. VW was the first to trial the idea and BMW, MINI, smart, Citroen and Peugeot have followed suit, all using electrical power to restart the engine, requiring beefed up starting systems to cope with ever-more-congested urban conditions (25% of European driving time is now spent at standstill). Now Mazda has come up with a better idea - restarting 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.
Idling stop systems save fuel by shutting down the engine automatically when the car is stationary, and restarts it when the driver resumes driving.
Mazda has independently developed the stop-start system, called the Smart Idle Stop System (SISS), and has found it to improve fuel economy by about ten percent (in Japan’s 10-15 mode tests) 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 the technology to market next year.
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.