HEUI technology introduction and technical advantages
Introduction to HEUI
The hydraulically driven electronically controlled unit injector (HEUI, also called medium-pressure common rail injector) fuel system uses engine lubricating oil pressurized to a high pressure to drive the injector plunger to produce high-pressure diesel fuel. technology.
This technology is the same as the high-pressure common rail system used in recent years. The fuel injection pressure, fuel injection volume and fuel injection timing of the fuel injector are no longer related to the engine speed, and are not restricted by the geometric parameters of the camshaft profile.
The use of hydraulic pressure to compress fuel and obtain excellent fuel injection characteristics is a powerful and effective method. Before the high pressure common rail system appeared, the HEUI system was the first technology that could truly achieve a fuel injection system independent of engine speed.
The HEUI fuel system can perform flexible fuel injection control according to the engine speed and load. By changing the software settings, it can optimize the control of fuel injection pressure, fuel injection volume, fuel injection curve and fuel injection timing.
Advantages of HEUI system
The HEUI system is the first revolutionary technological innovation of high-pressure diesel injection technology.
In the 1980s, major engine factories were looking for diesel fuel systems that could meet higher emission regulations. They gradually realized that mechanical diesel fuel systems had many drawbacks. The main drawback was mechanically driven diesel pumps or unit pumps. All are driven by the camshaft of the engine.
This system cannot flexibly change the fuel injection timing and fuel injection volume according to the requirements of emission regulations. Engine operating conditions, such as load, water temperature and air temperature, intake pressure, engine speed, atmospheric pressure, etc., cannot meet the requirements for fuel injection timing and fuel injection volume.
What’s more serious is that these mechanically driven fuel systems cannot get enough pressure to atomize diesel at low speeds, which will seriously affect the engine’s emission performance. Because the movement speed of the fuel plunger is related to the engine speed, the compression speed of the plunger is very low at low engine speeds, making it difficult to generate high pressure.
What the industry needs is a fuel system that can operate independently of engine speed. The HEUI system can fully achieve this goal, that is, whether the engine is running at the lowest or highest speed, the HEUI fuel system can generate high injection pressure. Therefore, the HEUI system can be adjusted immediately when the engine suddenly accelerates or the load changes.
Hydraulically driven fuel system
The HEUI system uses high-pressure engine oil instead of the camshaft system as the power source to compress the diesel and form high pressure.
Since the compression, metering, timing and atomization of fuel are integrated into the HEUI injector, the HEUI injector is generally defined as a unit injector.
Diesel and high-pressure oil are supplied to the HEUI injectors at the same time, and an engine-driven high-pressure oil pump supplies up to 275 kilograms of oil to the injectors. Inside the injector, the hydraulic pressure will be further amplified, allowing HEUI to compress the diesel to a very high pressure.
HEUI can effectively reduce engine noise
Since 1996, HEUI injectors have used two-stage injectors, that is, before the camshaft angle of 8-10 degrees before the main injection, the injector will have a relatively small amount of pre-injection, and Caterpillar will This feature is called pre-spray.
This kind of pre-injection will help the engine reduce vibration and noise, while effectively reducing nitrogen oxide emissions.
Electronically controlled hydraulic valve technology (no camshaft diesel engine)
HEUI technology can allow the control of the intake/exhaust valve to be integrated into the high-pressure oil control system.
International’s DT series truck engines use HEUI system high-pressure engine oil to achieve in-cylinder engine braking.
Subsequently, IWC Truck and Engine Company applied HEUI’s high-pressure oil control system to camshaftless diesel engines. This engine uses electronically controlled hydraulic valve technology to control the action of the intake valve/exhaust valve.
This engine shows absolute advantages in variable valve timing and variable valve lift. These technologies bring great innovations in engine control. The engine controls the intake and exhaust valves according to each engine operating condition and speed. Optimization has greatly reduced emissions and greatly improved the engine performance that was previously limited by the mechanical system and cam profile.
Since the hydraulic control of the intake/exhaust system technology does not require complex cam driving, it does not require too much driving torque during the engine starting process. In this way, the engine can be started by using a relatively small starter motor and a smaller battery. .
When the exhaust valve is slightly opened, the engine is more likely to be rotated by the starter motor. Therefore, we can close the exhaust valve of a certain cylinder or the exhaust valves of all cylinders at the right time to make the starting process faster and easier. .
These engines also have the function of temporarily cutting off certain cylinders according to different power requirements. When the engine has low power requirements, it can temporarily cut off a certain cylinder through the control of the intake and exhaust valves to save fuel consumption.
Application of HEUI system
IWC Trucks and Engines cooperated with Caterpillar to bring the HEUI system to the market in 1993. After that, engines equipped with HEUI fuel systems were widely produced and used.
The most popular HEUI system produced by this joint venture plant was applied to the 7.3-liter IWC engine T-444, which was widely used in Ford diesel vehicles from 1993 to 2003.
During this period, more than 2.2 million engines of this model were produced. In fact, two of every three Ford F-250 diesel vehicles are equipped with this engine. Follow-up investigations over the following years have demonstrated the good durability and reliability of this engine.
IWC also applies the HEUI system to its DT series engines, such as DT-466 and DT570. IWC also applies the HEUI system to its T-444E, DT-466-570, Max Force 5, 7, 9, 10, Max Force DT and VT365 engines.
Caterpillar applied the technology to 3116 and 3126 engines and many construction machinery engines.
Caterpillar applied the HEUI system to its famous 3116, 2126, C7 ACERT and C9 ACERT engines.
These engines are widely used in road vehicles and construction machinery. For example, Caterpillar engines are used in Freightliner, Sterling, GMC Top-kick and Ford’s medium-sized vehicles.
Caterpillar HEUI engines are also used in more other industrial applications, such as many Caterpillar crawler construction machinery.
The second-generation HEUI technology is called GENII or G2, and has more sophisticated processing and manufacturing technology. Siemens AG, IWC Truck & Engine Company and Sturman Industries formed a technology alliance to jointly develop the so-called digital valve technology. Subsequently, the 6.0L Powerstroke engine, 4.5L V6 engine and 6.0L V8 engine produced by IWC all used this HEUI injector, and these engines were subsequently used in many military vehicles and some medium-duty truck applications.
HEUI system components
The HEUI system is mainly divided into 4 subsystems, they include:
Low pressure oil supply system
High pressure oil system
Electric control system