Idle Stop-Start Systems

Idle Stop-Start Systems Basic Description The Idle Stop-Start System is a low cost method for increasing fuel  economy and d ecreasing emissions. The system turns off an internal combustion engine when the vehicle stops at a stop light  or during stop and go traffic where the vehicle would normally idle for a minimum of three  to five seconds, then the engine is restarted when the driver is ready to proceed.  An electronic control unit determines an appropriate time to turn off the engine based on  data from various sensors. An auto start/stop system can reduce CO2 emissions by up  to 3.5%. The system is currently available on most hybrid vehicles and on BMW's Efficient Dynamics vehicles. In hybrid vehicles, the system works very efficiently due to the availability of the large  rechargeable battery used to assist in powering the engine. The picture below demonstrates  how the system works on a full hybrid 2007 Toyota Prius. When the vehicle comes to a complete stop at a stop; the engine is turned off. Notice how the energy monitoring computer shows no  flow of energy. When the brake pedal is released, the electric power from the battery is used  to start the engine and assist in the initial acceleration. The yellow arrows show the flow of the  electric energy to the wheels. When engine power is required, the engine is quickly started and  assists the electric motor in powering the vehicle. The concept is simple; however numerous parameters must be monitored and controlled in  order to ensure the driver's comfort whenever the engine turns off. The system must monitor  the state of charge (SOC) of the battery, so that the engine can be started again. Also, the air  conditioning system must be shut down when the engine is off or being started. The system  monitors the cabin climate to ensure the driver's thermal comfort. If the cabin temperature  has not reached the operator's set value the auto start/stop system will not initiate. In addition,  the engine temperature is monitored to avoid cold starts. This ensures complete combustion  and optimal operation of the catalytic converter, thus reducing emissions. The system also requires the use of a relatively new device called an integrated  starter generator, which is a component that combines the starter and alternator into one unit. This system is able to draw direct power from the battery to start the vehicle and recharge the battery while the battery is running or during regenerative braking. Sensors Engine temperature, external temperature, cabin temperature, battery status, steering angle, seat belt connection, brake pedal position, accelerator pedal position, clutch  pedal position (non-hybrid), gear shift (non-Hybrid), wheel speed Actuators Starter, Valve Timing

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