Mazda has announced a clever new start-stop system that promises fuel economy gains of 10% or more without the need for an electric motor. The Smart Idle Stop System (SISS) uses only direct injection and combustion to restart your vehicle, while most start-stop systems use an electric motor and traditional engine start-up process. SISS stops the pistons in the optimal position for an engine restart, and then injects fuel into the cylinders before the engine begins to rotate and lets the power of combustion turn the engine over to start. This enables an SISS-equipped Mazda petrol engine to restart in 0.35 seconds, or half the time of start-stop systems using an electric motor. The catch: SISS only works with automatic transmissions.

Mazda's SISS system will be available in 2009, but the Japanese automaker hasn't yet announced which models will receive the fuel-saving technology, nor has it disclosed whether SISS will be available in the States at launch. With Americans becoming increasingly sensitive to fuel economy and petrol prices, we hope we're not left out in the cold. Hit the jump to review Mazda's press release.

[Source: Mazda]


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.

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