Liwei M0031P145 Diesel Injector Nozzle: Sac Volume Retention, Post-Seat Dribble & HC/Oil Dilution Control in Deep-Bowl Common-Rail Engines
1. Product:M0031P145
2. Compatible Equipment: Diesel Fuel Injection Systems
3. Manufacturer: Aftermarket OEM Replacement
4. Condition: Brand New, Fully Tested
5. Origin: ABOSEDE Diesel
6. Shipping period: 3-5 business days
7. Payment terms: T/T, Western Union, PayPal
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Product Introduction
The Liwei M0031P145 is a seven-hole, 145° diesel injector nozzle referenced for deep-bowl, high-swirl common-rail engines. It is a bare nozzle, not a complete injector. Its 145° narrow cone and 0.180 mm orifices provide deeper penetration than a 150° nozzle, which helps the plume reach the outer bowl radius in a deep-bowl piston. But narrow-angle nozzles have a less-discussed downside: sac volume retention. Fuel trapped in the nozzle sac after the needle seats can drip into the cylinder, raising unburned hydrocarbon (HC), oil dilution and cold-start smoke. The ECM can correct total fuel mass with IQA/trim and cylinder balance. It cannot correct post-seat dribble. This guide focuses on sac volume retention, post-seat dribble, HC/oil dilution control and installation verification.
📌 Fitment & Nozzle Identity
The M0031P145 must be matched to the correct injector body, needle, control valve, seat angle, opening pressure and needle lift. It is commonly referenced for Bosch CRI and Denso G2/G3 injector families with a 7 × 0.180 mm geometry. Confirm injector part number, nozzle number, needle diameter, seat angle, lapping requirement and copper washer specification before ordering. Do not install a bare nozzle without checking injector body wear and sleeve condition. Also confirm the combustion system. A 145° cone is intended for deep-bowl, high-swirl pistons. A mismatched bowl changes spray targeting and can increase wall impingement, soot and oil dilution.
📊 Sac Volume & Post-Seat Data
| Parameter | Service target | Diagnostic meaning |
|---|---|---|
| Nozzle type | Inward-opening, differential pressure | Common-rail nozzle family |
| Number of holes | 7 | Flow area and plume count |
| Orifice diameter | ≈ 0.180 mm | Atomization and axial velocity |
| Spray angle | 145° | Deep-bowl, high-swirl matching |
| Static flow @ 100 bar | ≈ 760 cc/min | Hydraulic baseline |
| Spray penetration @ 1,600 bar | ≈ 48 mm | Bowl reach and wall clearance |
| Sac volume | Minimised by design | Post-seat HC and oil dilution |
| Opening pressure | ≈ 215 ± 10 bar | Start of injection |
| Needle guide diameter | ≈ 4.0 mm | Concentricity and friction |
| Needle-to-nozzle clearance | ≈ 3–5 µm | Leakage and seizure risk |
| Seat angle | ≈ 60° conical | Sealing and after-dribble control |
| Seat diameter | ≈ 3.6 mm | Seat contact and sac volume |
| Needle lift | ≈ 0.20 mm | Partial-lift and pilot stability |
| Material | M42 high-speed steel | Hot hardness and wear resistance |
| DLC coating | ≈ 1.2 µm on guide | Friction and soot resistance |
| Max rail pressure | ≈ 1,800 bar | Pressure compatibility |
⚙️ Sac Volume Retention & Post-Seat Dribble
The sac is the small volume between the needle seat and the spray holes. After the needle closes, fuel remains in the sac. In a VCO (Valve Covered Orifice) nozzle, the needle covers the holes directly, so sac volume is small. In a sac-type nozzle, fuel remains in the sac and can drip into the cylinder after the main injection. The M0031P145's 145° narrow angle and 0.180 mm holes place the seat close to the holes, but sac volume still depends on seat diameter, needle lift and seat grinding quality. If the seat does not seal 360° or if the needle lifts unevenly, residual fuel drips. That fuel does not burn completely. It appears as HC, white smoke at cold start, rising oil level and higher DPF soot load. The ECM cannot detect post-seat dribble because it happens after the command ends.