Now that we have covered the Driver Wish, Torque Limiters, and Smoke Limiters, we reach a fundamental pillar of TDI file engineering: the Injection Duration maps (often referred to as IQ to Angle maps).
When you increase the fuel quantity (for example, pushing past stock limits from 45 mg/str to 65 mg/str), you cannot simply expect the stock software to magically know how long to keep the unit injectors open. If you don't scale or adjust the duration maps, the injectors will close too early, or worse, you will inject fuel too late into the expansion stroke, destroying efficiency and causing massive exhaust gas temperatures (EGT).
Let's break down how Injection Duration works on the Bosch EDC15P+ architecture and how to handle it properly.
1. Concept and Operation of Injection Duration
Unlike older rotary pump (VP37) engines where duration is often managed differently or expressed in milliseconds, the unit injector (Pumpe-Düse / PD) systems in the EDC15P+ calculate injection duration in Degrees of Crankshaft Angle (°KW).
X-Axis (Columns): Injected Quantity (IQ) (measured in $mg/str$).
Y-Axis (Rows): Engine Speed (measured in RPM).
Map Body (Z-Axis): Injection Duration (measured in °KW - Degrees of Crank Angle).
The Physics Behind It: As engine RPM increases, the time available for a combustion event shrinks dramatically. Because diesel fuel takes a finite amount of time to pass through the injector nozzle under high mechanical pressure, you need more degrees of crankshaft rotation at high RPM to inject the exact same mass of fuel.
2. Configuring Factors in WinOls
To read and modify the duration maps accurately without misinterpreting the raw hex values, apply these standard factors in WinOls:
X-Axis (Injected Quantity / IQ):
Factor:
0.010000(or0.01)Unit:
mg/str
Y-Axis (RPM):
Factor:
0.250000Unit:
RPM
Map Body (Z - Duration):
Factor:
0.023437(or similar depending on the exact software variant, traditionally scaling raw bits to degrees of crank angle).Unit:
°KW(Degrees)
3. Best Practices for Modification
Understand the Stock Limits: Stock EDC15P+ duration maps usually end around $50$ to 55 mg/str (depending on whether it's a 130hp ASZ/BLT or 150hp ARX/ARL engine). If your Torque and Smoke limiters allow 65 mg/str, but your duration map stops at 55 mg/str, the ECU will extrapolate data or cap the injection time, leading to erratic fueling behavior at the top end.
Extrapolating vs. Scaling: When tuning for higher outputs, you need to extend the X-axis columns to higher fuel quantities (e.g., 70 or 75 mg/str) and recalculate the required degrees carefully. Avoid blind copying of duration maps from other engine codes, as nozzle sizes (e.g., stock 0.38 vs upgraded 80\% nozzles) completely change the flow rate per millisecond.
Watch Out for SOI (Start of Injection): Extending durations too far towards Top Dead Center (TDC) without advancing your Start of Injection maps will cause late burning, dropping power while skyrocketing cylinder pressures and exhaust temperatures.