Injection Quantity (IQ) defines how much fuel the ECU delivers per cycle. IQ is the bridge between torque model, rail pressure and injection timing, making it critical for both performance and emissions.

Overview

The ECU transforms torque request into fuel mass using airpath models, smoke limitations and protection strategies.

Controlled Signals

• Driver wish torque
• Air mass
• Rail pressure
• SOI and EOI maps
• Temperature corrections

Maps Involved

• IQ to Torque Conversion Maps
• Smoke Limiter
• Temperature Correction Maps
• SOI Timing Maps
• Maximum IQ Limiters

ECU Logic Sequence

Torque Request → Airflow Check → Smoke Limiter
         ↓
IQ Calculation → Rail Pressure Check
         ↓
SOI/EOI Adjustment → Injection Execution

Calibration Objectives

• Correct torque model → correct IQ
• Stable rail pressure during transient load
• Clean emissions behavior

Calibration Strategy

• Always fix smoke model before raising IQ
• Increase IQ only if airflow and boost allow
• Correct SOI to avoid excessive pressure rise

Diagnostics

• IQ deviation faults
• Smoke limiter activation
• High EGT under load

Best Practices

• IQ is not a “power dial” — it must match airflow
• Monitor EGT and boost during high-IQ tuning