HEUI Fuel Injection System Introduction

HEUI Fuel Injection System Introduction
I. Brief Introduction to the HEUI Fuel Injection System
HEUI (Hydraulically Actuated Electronic Unit Injector) is a hydraulically driven, electronically controlled unit injection system developed by Caterpillar in the 1990s. It represents a transitional technology from mechanical injection to high-pressure common rail injection. Its core uses high-pressure engine oil as the driving energy source, decoupling injection pressure from engine speed.

1. Core Structure

It mainly consists of a high-pressure oil pump (HPOP), HEUI injectors (one per cylinder, including a booster piston), an electronic control unit (ECU/ECM), and a low-pressure fuel system. Its structure is simple and does not require camshaft drive.

2. Working Principle

The high-pressure oil pump pressurizes the engine oil to 21–25 MPa. The ECU controls the opening and closing of the solenoid valve, causing the high-pressure oil to push the booster piston of the injector, pressurizing the low-pressure fuel to 140–180 MPa before atomizing and injecting it into the cylinder. The injection quantity is adjusted by the duration of energization of the solenoid valve.

3. Core Advantages and Disadvantages

Advantages: Maintains high injection pressure even at idle/low speeds, resulting in good atomization and low emissions; allows for flexible control of injection timing and fuel quantity, leading to strong power and low fuel consumption. Limitations: Depends on engine oil quality, resulting in high maintenance costs; pressure control precision is inferior to high-pressure common rail systems, leading to poorer consistency across multiple cylinders.