Fuel system with direct and high pressure port fuel injection with thermal management

A fuel system for delivering liquid fuel to a combustion chamber of an internal combustion engine, the fuel system comprising:

• a port fuel injector in an air intake communicating with the combustion chamber;
• a first fuel rail containing pressurized liquid fuel in communication with the port fuel injector;
• a direct fuel injector arranged to inject fuel directly into the combustion chamber;
• a second fuel rail containing pressurized liquid fuel in communication with the direct injector;
• a high-pressure fuel pump having a high-pressure outlet in communication with the second fuel rail;
• a regulator valve in communication with the high-pressure outlet and the first fuel rail, said regulator valve controllable to reduce a fuel pressure of fuel delivered to the first fuel rail relative to a fuel pressure at said high-pressure outlet;
• and
• a control system configured with computer-readable instructions stored in non-transitory computer readable media, said instructions executable to:
• monitor fuel pressure in the first fuel rail;
• and
• control the regulator valve to deliver fuel to said first fuel rail to maintain a predetermined quantity of fuel at said predetermined pressure in said first fuel rail.