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.