Connecting to and decoding the CAN bus data on a first-year Porsche 987.1 can be a challenging task. This article outlines a personal experience with using an RCP3 device to tap into the Engine Control Unit (ECU) and decipher some key engine parameters.
One initial hurdle encountered was establishing communication with the CAN bus. The default CAN device setting in the script needed to be changed from ‘0’ to ‘1’. Furthermore, changing the baud rate to 100,000 caused unexpected behavior, including rear wing deployment. This highlighted the sensitivity of the ECU to incorrect communication settings. The solution involved modifying the ‘rxCan’ function within the script to reflect the correct CAN device (changing rxCan(0,100) to rxCan(1,100)). This seemingly minor adjustment enabled successful data logging.
Once communication was established, the focus shifted to identifying and interpreting specific data packets. Preliminary findings suggest the following:
- CAN ID 578, Offset 5, Length 2: This data packet likely represents throttle position.
- CAN ID 578, Offset 3, Length 2: This packet is believed to contain the first two digits of the engine RPM. Further investigation is needed to confirm if the remaining two digits are logged and their location within the data stream. Endianness (byte order) might play a role in interpreting this value accurately.
- CAN ID 1089, Offset 5, Length 2: This packet possibly indicates engine or engine oil temperature. More data analysis is required to verify this assumption.
Currently, the data logging process involves manually transferring data to a spreadsheet and filtering it by CAN ID to discern patterns. This manual process highlights the need for a more automated solution.
It’s also confirmed that the 987.1 lacks a steering angle sensor and an oil pressure sensor. Future enhancements to the car could include installing these sensors to gather more comprehensive data.
The following formulas have been used to convert the raw data into meaningful values:
- RPM:
*10/40+30(This formula provides results comparable to those obtained using a Durametric tool.) - Throttle:
*1.0/255(This formula accurately represents the throttle position.)
This initial exploration into the first-year Porsche 987.1’s OBDII system via the CAN bus demonstrates the potential for extracting valuable engine data. Further experimentation and analysis will refine the data interpretation and potentially uncover more insights into the vehicle’s performance.
