▁partially ▁opened , ▁bringing ▁the ▁secondary ▁tur bo ▁up ▁to ▁near - oper ating ▁speed . ▁The ▁EC U ▁– ▁working ▁with ▁another ▁duty ▁sol en oid ▁and ▁vac u um ▁dia ph rag m ▁– ▁determ ines ▁the ▁amount ▁that ▁the ▁exhaust ▁control ▁val ve ▁opens . ▁The ▁EC U ▁calcul ates ▁this ▁amount ▁of ▁val ve ▁opening ▁based ▁on ▁the ▁input ▁of ▁a ▁differential ▁pressure ▁sensor ▁that ▁takes ▁fe eds ▁from ▁the ▁int ake ▁manifold ▁and ▁the ▁out let ▁of ▁the ▁secondary ▁tur bo . ▁ ▁Any ▁boost ▁pressure ▁produced ▁by ▁the ▁secondary ▁tur bo char ger ▁during ▁the ▁trans itional ▁stage ▁is ▁redirect ed ▁to ▁the ▁atmos pher ic ▁side ▁of ▁the ▁compress or ▁in let ▁( between ▁the ▁tur bos ▁and ▁air ▁filter ). ▁ ▁With ▁the ▁primary ▁tur bo ▁continu ing ▁to ▁supply ▁manifold ▁pressure ▁and ▁the ▁secondary ▁tur bo char ger ▁essentially ▁ble eding ▁off ▁the ▁boost ▁it ▁makes ▁during ▁the ▁transition , ▁the ▁EC U ▁will ▁determine ▁when ▁to ▁close ▁the ▁pressure ▁relief ▁val ve ▁and ▁fully ▁open ▁the ▁exhaust ▁control ▁val ve . ▁Once ▁this ▁is ▁done , ▁the ▁EC U ▁will ▁again ▁look ▁at ▁the ▁input ▁from ▁the ▁differential ▁pressure ▁sensor ▁and ▁open ▁yet ▁another ▁val ve ▁– ▁the ▁int ake ▁control ▁val ve ▁( which ▁is ▁mounted ▁between ▁the ▁secondary ▁tur bo ' s ▁compress or ▁out let ▁and ▁the ▁inter co ol er ). ▁ ▁With ▁the ▁int ake ▁control ▁val ve ▁open , ▁boost ▁pressure ▁from ▁the ▁secondary ▁tur bo ▁is