Cars · Sensors
OBD1 16-Bit RPM Calculation
Technical reference for calculating 16-bit RPM values in OBD1 Honda ECUs using the standard conversion formula and Little Endian byte order.
To convert a 16-bit raw value into engine speed (RPM) for OBD1 Honda ECUs, use the following formula:
RPM(x) = 1,875,000 / x
Where x represents the raw 16-bit value retrieved from the ECU memory.
Important
All 16-bit values in OBD1 ECUs are stored in Little Endian byte order. When reading these values from a data stream or memory dump, ensure the bytes are swapped accordingly (Least Significant Byte followed by Most Significant Byte).
Calculation Reference
| Raw Value (x) | Calculated RPM |
|---|---|
| 625 | 3,000 |
| 468 | 4,006 |
| 375 | 5,000 |
| 312 | 6,009 |
| 267 | 7,022 |
Tip
This calculation is essential for custom data logging and real-time tuning applications where raw memory addresses are being polled directly from the MCU.