Pilot injection (also called pre-injection) delivers a small fuel quantity before the main injection event. This pre-heats the combustion chamber, reduces ignition delay and significantly lowers the characteristic diesel “knock” noise.

Обзор

Modern diesel ECUs use 1-3 pilot injections before the main event. The quantity and timing are carefully calibrated to balance noise reduction with emissions and fuel consumption.

Controlled Signals

• Pilot injection quantity (mg/stroke)
• Pilot injection timing (°BTDC)
• Number of pilot events
• Separation angle from main injection

Maps Involved

• Pilot Quantity Maps vs RPM/load
• Pilot Timing Maps
• Pilot Enable/Disable Maps
• Temperature-based Pilot Corrections

Logic Sequence

Operating Conditions → Pilot Enable Check
         ↓
Pilot Quantity & Timing Lookup
         ↓
Rail Pressure Compensation
         ↓
Injector Command Sequence

Calibration Objectives

• Minimize combustion noise
• Improve cold start smoothness
• Maintain fuel efficiency

Calibration Strategy

• Increase pilot quantity slightly for quieter combustion
• Adjust separation angle if knock persists
• Disable or reduce pilots at high RPM/load for efficiency

Диагностика

• Excessive idle noise after pilot changes
• Rough cold start
• Increased fuel consumption

Best Practices

• Pilot changes affect the entire combustion event — test thoroughly
• Coordinate pilot timing with main SOI