An ECU file is the binary content of the ECU's flash memory. Typically 1-8 MB, contains the manufacturer's firmware (Bosch, Continental) + vehicle-specific calibration maps.
ORI vs MOD file
- ORI file (Original): file extracted from the ECU, identical to the factory one
- MOD file (Modified): file modified by the tuner, ready to be flashed
Extensions file
- .bin: raw binary
- .hex: Intel HEX (vintage)
- .ori: tuner convention for the original file
- .mod: tuner convention for the modified file
- .fpf: New Genius/FlashPoint format
- .frf: VAG ODX format
What does a modified file change
Turbo pressure maps, ignition advance, injection duration, rail pressure, required torque maps, limiters, EGR/DPF. Well done modification: +20-40% power, maintaining reliability.
File structure
An ECU file contains a program part (the manufacturer's firmware) and a calibration part (the maps). Tuning almost always affects the calibration, leaving the program intact. To orient yourself among thousands of maps, software such as WinOLS is used, which automatically identifies the tables and compares ORI and MOD.
Good practices
Each MOD file originates from the corresponding ORI read by the customer's ECU: using an original from another example, even with the same code, can lead to inconsistent checksums or adaptations. After the modification, the checksums are recalculated and, where present, the firmware signature is managed. Keeping ORI and MOD sorted by vehicle is essential for restorations, warranties and future assistance.
File organization
Keeping files tidy is part of the job: ORI and MOD must be kept for each vehicle with indication of date, tool, reading method and checksum. A well-structured library speeds up restores, warranty management and future work, and avoids errors such as flashing the wrong MOD. In file service portals this archiving is automatic and linked to the customer's details and the vehicle's VIN.