Delphi and Caterpillar common rail injector internal lift parameter definitions

I. Delphi

1. Armature Lift

1) Definition: The distance the valve core can move during the operation of the injector. The armature lift of Delphi rail injectors is generally between 30 and 70 micrometers.

2) Schematic Diagram:

3) Adjustment Trend: As shown in the diagram above, the armature lift of a Delphi injector is actually the distance between the valve core disc and the upper edge of the valve seat in the free state (or the depth to which the valve core disc is recessed relative to the valve seat). Therefore, it depends entirely on the machining control of the valve assembly and cannot be adjusted (of course, if the armature lift is off-center, you can try polishing the end face of the valve core disc with fine sandpaper of 1500 grit or higher).

4) Impact on Injection Characteristics: The size of the armature lift affects the injection volume at various points; the larger the armature lift, the larger the injection volume.

When there is a deviation in the injection volume, replacing it with a valve assembly with a different armature lift can change the injection volume.

2. Air Clearance

1) Definition: When the valve core disc (i.e., armature disc) moves to its upper end (the small step contacts the solenoid valve), the main body of the valve core disc does not contact the end face of the solenoid valve, but leaves a certain gap. The size of this gap is the air clearance.

2) Schematic Diagram:

3) Adjustment Trend: Similar to the armature lift, the air clearance of Delphi injectors is controlled by the manufacturing process of the valve assembly and cannot be adjusted, as shown in the diagram above.

4) Impact on Injection Characteristics: The larger the air clearance, the smaller the injection volume. However, the impact is not as significant as the armature lift.

3. Needle Valve Lift

1) Definition: The displacement of the needle valve during the operation of the injector is called the needle valve lift.

2) Schematic Diagram:

3) Adjustment Trend: The needle valve lift of Delphi injectors cannot be adjusted. Its size is determined by the depth of the return baffle hole and the extension of the needle valve.

4) Impact on Injection Characteristics: The larger the needle valve lift, the larger the injection volume. 4. Solenoid Valve Spring Force

1) Definition: The solenoid valve spring has a preset force used to press the sealing ball to seal the high-pressure fuel in the valve seat control chamber. The spring force cannot be too small, otherwise high-pressure fuel will leak from the seat. It also cannot be too large, otherwise the ball will open slowly or not at all. The solenoid valve spring force can be adjusted by changing the thickness of the adjusting block.

2) Schematic Diagram:

3) Adjustment Trend: The longer the adjusting block, the greater the solenoid valve spring force.

4) Influence on Injection Characteristics: The greater the solenoid valve spring force, the smaller the injection volume. The smaller the solenoid valve, the larger the injection volume. The effect is particularly significant on medium-speed injection volume.

5. Fuel Injector Spring Force

1) Definition: The fuel injector spring has a preset force used to press the needle valve to seal the injection orifice and prevent fuel injection. The spring force cannot be too small, otherwise fuel leakage will occur at the injector seat. It also cannot be too large, otherwise the needle valve will open slowly. The preset force of the Delphi injector nozzle spring is determined by the depth of the return baffle hole and does not require adjustment.

2) Schematic diagram: As shown in the diagram above.

3) Adjustment trend: The thicker the shim, the greater the preset force of the spring.

4) Influence on injection characteristics: The greater the spring force, the smaller the injection volume.

II. Caterpillar CR200

1. Armature lift

1) Definition: The distance the valve core can move during the operation of the injector. The armature lift setting value of the Caterpillar CR200 common rail injector is generally between 35 and 45 micrometers. The armature lift of the Caterpillar CR200 is adjusted by an adjusting disc sandwiched between the upper and lower valves.

2) Schematic diagram:

3) Adjustment trend: The thicker the adjusting disc, the greater the armature lift.

4) Influence on injection characteristics: The size of the armature lift affects the injection volume at various points; the greater the armature lift, the greater the injection volume. If the armature lift is too large or too small, the injector's injection performance will become abnormal. Too small an armature lift will cause a throttling effect, while too large an lift will affect the opening speed and easily cause cavitation. Therefore, the premise for adjusting the fuel quantity by adjusting the shims is that the armature lift is within the effective range. Generally, when the armature lift is between 30 and 70 micrometers, the injector's injection performance will not be abnormal.

2. Air Clearance

1) Definition: When the armature disc moves to its upper end (blocked by the spring seat and spring bushing), there is no contact between the armature disc and the solenoid valve end face, but a certain gap remains. This gap is the size of the air clearance. It is mainly used to prevent the armature disc from sticking to the solenoid valve.

When the solenoid is not energized, the armature disc sits under the action of the valve spring. At this time, the gap between the armature disc and the solenoid valve end face is the sum of the armature lift and the air clearance.

The air clearance of the Caterpillar CR200 injector is between 50 and 70 micrometers.

2) Schematic Diagram:

3) Adjustment Trend: The thicker the shim, the larger the air clearance.

4) Impact on Injection Characteristics: The larger the air clearance, the smaller the injection volume.

3. Needle Valve Lift

1) Definition: The displacement of the needle valve during injector operation is called the needle valve lift.

2) Schematic Diagram:

3) Adjustment Trend: The thicker the shim, the larger the needle valve lift.

4) Impact on Injection Characteristics: The larger the needle valve lift, the larger the injection volume, especially in full-load or high-load areas.

4. Solenoid Valve Spring Force

1) Definition: The solenoid valve spring has a preset force used to press the sealing cone surface to seal the high-pressure fuel in the valve seat control chamber. The solenoid valve spring force cannot be too small, otherwise the high-pressure fuel will leak from the seat surface. It also cannot be too large, otherwise the armature core will open slowly or even fail to open. The magnitude of the solenoid valve spring force can be adjusted by changing the thickness of the valve spring shim.

2) Schematic Diagram:

3) Adjustment Trend: The thicker the shim, the greater the solenoid valve spring force.

4) Impact on Injection Characteristics: The greater the solenoid valve spring force, the smaller the injection volume. The smaller the solenoid valve, the greater the injection volume. The effect is particularly significant on the injection volume at medium speeds.

5. Injector Spring Force

1) Definition: The injector spring has a preset force used to press the needle valve to seal the nozzle orifice and prevent fuel injection. The injector spring force cannot be too small, otherwise fuel leakage will occur at the injector seat. It also cannot be too large, otherwise the needle valve will open slowly. The preset force of the Delphi injector injector spring is determined by the depth of the return baffle orifice and does not require adjustment.

2) Schematic Diagram: As shown in the diagram above.

3) Adjustment Trend: The thicker the shim, the greater the spring preset force.

4) Impact on Injection Characteristics: The greater the spring force, the smaller the injection volume.