Automatic start-stop systems for engines are becoming increasingly common on vehicles in Europe. However, these systems typically use the conventional starter motor to re-start the engines after a stop. This can result in slow re-starts and additional load on the starter. Mazda has devised a new system that they claim will provide quicker, more consistent re-starts. The Mazda system relies on direct injection to function. When the engine is stopped, sensors are used to stop the engine with the pistons in a precise location. This will allow one of the cylinders to have a known amount of air in the combustion chamber. When the time comes to re-start, fuel is injected directly into the cylinder and ignited. The expansion of the burning fuel is used to get the engine turning to re-start the engine. Mazda claims the engine can re-start in 350 milliseconds, about half the time of a conventional starter. The re-starts are indexed to consecutive cylinders so that the same cylinder isn't used every time. Mazda claims a 10 percent reduction in fuel consumption on the Japanese urban test cycle.
Mazda Develops UNIQUE Smart Idle Stop System Using Direct Injection Engine Technology
HIROSHIMA, Japan-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.|