Patent ID: 7788922

Claim:
A method of optimizing boost pressure of an internal combustion engine having a turbo-charger with a compressor and an exhaust driven turbine with a waste-gate flow path that bypasses the turbine in a parallel path, and a waste-gate mass flow rate {dot over (m)} WG through the waste-gate flow path being adiustable by a waste-gate valve, comprising the steps of: providing an engine controller being in electrical communication with the engine; providing a desired boost pressure P Boost des from the engine to the engine controller: calculating a desired waste-gate mass flow rate {dot over (m)} WG des in the waste-gate flow path with the engine controller, said calculated desired waste-gate mass flow rate {dot over (m)} WG des being a function of the provided desired boost pressure P Boost des ; and generating the control signal from the controller being received by the waste-gate valve, wherein the engine controller is adapted to operatively control the waste-gate valve using the control signal such that the waste-gate mass flow rate {dot over (m)} WG through the waste-gate flow path attains the calculated desired waste-gate mass flow rate {dot over (m)} WG des , wherein said step of calculating the desired waste-gate mass flow rate {dot over (m)} WG des further includes the desired waste-gate mass flow rate {dot over (m)} WG des being a desired waste-gate mass flow rate at standard sonic conditions {dot over (m)} WG des@SonicStdCond across the waste-gate valve, and calculating the desired waste-gate mass flow rate at standard sonic conditions {dot over (m)} WG des@SonicStdCond using a desired pressure ratio Pr T des includes the sub-steps of, determining a desired compressor mass flow rate {dot over (m)} C des with the engine controller; determining a desired compressor pressure ratio Pr C des using the provided determined, desired boost pressure P Boost des with the engine controller; determining a desired compressor power P C des with the engine controller using the determined desired compressor mass flow rate {dot over (m)} C des and the determined desired compressor pressure ratio Pr C des and predetermined compressor characteristics data; determining a desired corrected turbine mass flow rate {dot over (m)} T,cor des with the engine controller using the determined desired compressor power P C des , the desired corrected turbine mass flow rate {dot over (m)} T,cor des being a function of a product term (A*B), and the product term (A*B) including a turbine power term (A) having the determined desired compressor power P C des and a turbine boundary term (B) having a turbine outlet pressure P T,out ; determining a desired turbine pressure ratio Pr T des with the engine controller using the determined desired corrected turbine mass flow rate {dot over (m)} T,cor des ; and determining the desired waste-gate mass flow rate at standard sonic conditions {dot over (m)} WG des@SonicStdCond with the engine controller using the desired turbine pressure ratio Pr T des .