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A low pressure exhaust gas recirculation system (LP EGR system) enables the expansion of the EGR operating area than that of the widely used high pressure EGR system. As a result, fuel consumption and emissions can be improved. In order to meet the EU 5 emissions regulations, an exhaust throttle LP EGR system was used. The EU5 vehicles developed using this system have greater merits than other vehicles. However, because the exhaust throttle LP EGR valve is installed adjacent to the after-treatment system, the material of the LP EGR valve itself must be stainless steel in order to withstand the thermal stress, consequently, the cost is increased. Therefore, in order to achieve cost rationalization for EU6 vehicles, an intake throttle LP EGR system is developed and applied to replace the exhaust throttle LP EGR system. In order to apply the intake throttle LP EGR system, the EGR valve is installed in front of the turbo charger compressor.

This paper focuses on the vehicle test result of the US fuel economy test cycles such as FTP75, HWY and US06 with model based Cooled EGR system. Cooled EGR SW function was realized by Model Based Development (internal rapid prototyping) using iRPT tool. With EGR, mixing exhaust gas with clean air reduces the oxygen concentration in the cylinder charge, as a result, the combustion process is slowed, and the combustion temperature drops. This experiment confirmed that the spark timing was more advanced without knocking and manifold pressure was increased in all cases with EGR. A positive potential of fuel economy improvement on FTP mode, US06 mode have seen in this experiment but not for HWY where the engine load is quite low and the spark advance is already optimized. As a result, fuel economy was increased by maximum 3.3% on FTP, 2.7% on US06, decreased by 0.3% on HWY mode respectively with EGR.