HPL (high pressure loop)
LPL (low pressure loop)
The main type of EGR system used today is the high pressure loop (HPL) EGR system where the exhaust gas to be recirculated is taken from an upstream section of the exhaust passage. However, this system has a disadvantage: diverting a fraction of the exhaust gas before the turbocharger that uses exhaust gas energy to force extra air into the engine reduces the amount of exhaust gas energy which can be used by the turbocharger, which makes it difficult for the forced induction device to produce high power. Therefore, the combination of a high pressure loop EGR with low pressure loop (LPL) EGR that takes the exhaust gas to be recirculated from a downstream section of the exhaust passage, is expected to be widely used in the future. (Source: DENSO)
The new unit, the first in the world to integrate an air intake throttle valve and an EGR valve.
By integrating the two valves into one unit, DENSO combined the ducts and reduced the connectors, resulting to reducing the size to half compared to previous models. As the EGR system needs to be installed in a limited space close to the engine, a smaller system enables automakers to design engines more flexibility. (Source: DENSO)