Unit Injector Hydraulic Oil Supply
(1) “Jumper” tube. (2) Hydraulic electronic unit injector. (3) High pressure oil manifold.
The high pressure oil pump is a gear-driven axial piston pump. It raises the engine oil pressure level from typical engine operating oil pressure level to the actuation pressure level required by the unit injectors. This high pressure oil flows through lines into the high pressure oil manifold (3) located near the hydraulic electronic unit injectors (2). The manifold stores the oil at actuation pressure ready for unit injector operation. Oil is distributed equally and continually to the top of all unit injectors through “jumper” tubes (1) under the valve cover. After pressurizing a unit injector, the oil is discharged from the unit injectors onto the cylinder head, where it drains back to the oil pan. No oil return lines are required.
HEUI uses a high-pressure hydraulic system. The oil for this system is drawn from the engine lubrication system on the left side of the block and raised to high pressure by a gear-driven pump. The pressure is regulated by the ECM to the optimum pressure for a given set of conditions as determined by operational maps stored in memory. Available pressure ranges from approximately 5 MPa (725 psi) to 23 MPa (3335 psi). This is a closed-loop system; the ECM senses hydraulic pressure from the injection actuation pressure sensor on the high pressure oil manifold, and regulates pressure via a signal from the ECM to the injection actuation control valve mounted on the high pressure hydraulic pump.
High pressure oil is routed from the pump output through a steel tube to the oil manifold on the inlet manifold. oil is allowed to dump inside of the inlet manifold base and return to the oil sump. There are no return oil lines.