Cars · Sensors
OBD0 Fuel Calculation Formula
Technical reference for the OBD0 fuel calculation formula, including pulsewidth derivation and variable definitions.
The OBD0 fuel pulsewidth calculation is determined by the relationship between the decimal value at the memory address and the column multiplier.
Fuel Formula
The pulsewidth in milliseconds (ms) is calculated using the following formula:
pulsewidth (ms) = (Dec At Addy + (224/a)) / (208/a)
Variable Definitions
- a: The multiplier constant, defined as
2 ^ Column Multiplier. - Dec At Addy: The raw decimal value retrieved from the specific fuel map memory address.
Note
The Column Multiplier is a specific ROM parameter used to scale fuel map values. Ensure the correct multiplier is identified for the specific ROM bin being analyzed.
Reference Data
| Variable | Description |
|---|---|
| a | Calculated multiplier constant |
| Dec At Addy | Raw decimal value from ECU memory |
| 224 | Constant offset for pulsewidth calculation |
| 208 | Constant divisor for pulsewidth calculation |
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