The injectors are precision electronic valves that spray fuel into the cylinder. Types:
- Solenoidal: standard diesel/petrol, driven by electromagnet
- Piezoelectric: faster and more precise (Bosch CRI3.20, Continental Piezo)
- GDI: petrol direct injection, high pressure
Injector coding
Each injector has a IMA code printed above (e.g. "alphanumeric 7") indicating its individual flow characteristics. When you replace an injector, the new IMA code must be programmed into the ECU to ensure correct metering.
Injectors and Tuning
Stage 1 normally lies within the original range of the injectors. High power Stage 2-3 requires increased injectors (also called "oversize"), whose IMA code must be reprogrammed.
IMA/IQA coding
Each injector has a calibration code (IMA on VAG, IQA or classes on other brands) which describes its real flow tolerances. This code must be entered into the ECU in correspondence with the cylinder: an incorrect coding causes irregular operation, smoke and noise. When replacing one or more injectors, reprogramming of the codes is therefore mandatory.
Injectors and power
In the high stages, the flow rate of the injectors becomes the real bottleneck: beyond a certain level, oversized injectors are needed, with relative recoding and calibration. On diesels, cylinder-by-cylinder balancing and flow rate correction are parameters that the ECU adapts over time; a well-done tuning respects these adaptations instead of forcing them, preserving smooth operation and durability.
Good practice
When replacing an injector, reprogramming the calibration code is mandatory: skipping this step causes irregular operation and uneven wear. On remapped engines it is advisable to monitor the flow rate corrections cylinder by cylinder: values that differ greatly indicate an injector in difficulty. In the advanced stages, the transition to oversized injectors must always be accompanied by the relevant calibration in the ECU file.
In short, the injectors are precision components: correct coding, clean diesel and monitoring of flow corrections are the basis for making them last, even more so on a remapped engine that works at high pressures.