OBD-II cable: $50 (This one comes with an Arduino library, so it's easy to program with.) 7-Segment Display : $13 Arduino Protoshield : $10 (To easily mount the display on top of the Arduino.

If you are working with OBD2 hardware or software, it’s easy enough to access test data, simply plug into a motor vehicle with an OBD2 socket. If, however, you wish to test OBD2 software unde… ...

The OBD-II/CAN bus is more than fast enough for real-time tachometer, the problem is in your display device/software. There are multiple update speeds available. Some external OBD/CAN devices can ...