Development of New Generation Hybrid System (THS II) - Development of Toyota Coolant Heat Storage System

As the interest in global environmental protection increases, so do the worldwide social requirements of annually decreasing fuel consumption and producing cleaner exhaust gas. In California, a new special category of emissions standard, PZEV was implemented, as the most stringent emissions standard in the world. To meet this standard, it is crucial to decrease exhaust gas unburned hydrocarbon emissions, especially in cold start conditions. Toyota has sought a new approach to decrease these emissions and developed the Toyota Coolant Heat Storage System (CHSS). This system recovers hot engine coolant, in a heat-insulated reservoir, used for the next cold start, during and / or after engine operation and stores it in a reservoir during the engine-off soak period. During a cold start, the reserved hot coolant is directed to the cylinder head to rapidly warm the intake ports, and reduce enrichment, resulting in much lower HC emissions in cold conditions, This system is adopted on Prius with THS II (Toyota Hybrid System II), launched in August 2003, complying with California's ATPZEV, one of cleanest car categories in the world.