Cars · Diagnostics
OBD0 16-Bit RPM Conversion Formula
Technical reference for converting engine speed (RPM) to 16-bit hexadecimal values for OBD0 Honda ECU tuning and ROM modification.
To translate engine speed (RPM) into the 16-bit hexadecimal values required for OBD0 Honda ECU ROM tables, use the following calculation:
ECU Hex Value = 1920000 / RPM
Important
The resulting value must be converted to hexadecimal format for entry into ECU mapping software or binary editors.
Spreadsheet Implementation
When working with custom ROM tables in Microsoft Excel or Google Sheets, use the following formula to automatically calculate the required hex string:
=DEC2HEX(1920000 / [Cell_Reference])
Reference Table
| RPM | Calculation | Hex Value |
|---|---|---|
| 1000 | 1920000 / 1000 | 0768 |
| 3000 | 1920000 / 3000 | 0280 |
| 5000 | 1920000 / 5000 | 0180 |
| 7000 | 1920000 / 7000 | 0113 |
| 9000 | 1920000 / 9000 | 00D5 |