M150 - BMW S54 Throttle tracking issues

Hi

We have an issue with the Throttle Servo / position tracking on a BMW S54. This has a motor below the throttle bodies with a position sensor attached and a position sensor attached to the butterflies, the connecting rod has been made solid.

The throttle cuts out and comes back to life a second later. During the day we replaced the TPS on the motor (no change) then the motor with a different TPS on it (no change) then the TPS on the butterflies (no change) after each time we re calibrated the Main Offset and the Scale, also tried different PID settings from another car that has no issues. We compared the PID settings with 4 other calibrations and they were all different but we still have this issue.

I have attached a photo of the log so you can see what I am looking at and also the log file. In this example it happens on lap 16 and looks like the throttle position % is falling away as the throttle aim is climbing and soon after the error comes in. On the photo attached it shows down the bottom a Sensor fault on the Throttle Servo Bank 1 Diagnostic but logging no fault on the Main or Tracking position sensors.

I did the wiring on this car and a little concerned that its a wiring fault but I would have thought the log would show sharp voltage spikes if the wiring was loose somewhere?

Thanks for your help

Gareth

In I2, be sure to turn on "Component->Display->Show Status/Errors" (short cut, type "E" while a time/distance graph has focus). This makes it obvious that you have a significant amount of time with "Throttle Servo Bank 1 Position Sensor Tracking Diagnostic" indicating "Open Warning". M1 Tune help says this means "Normalized Result is more than 2% above High, Scale may be incorrect."

And also "Throttle Pedal Sensor Main Diagnostic" indicating "Closed Warning". M1 Tune help says "Normalized result is more than 2% below Low - Offset may be incorrect".

Since you are concerned about wiring -- what both of these could have in common is the configured power supply (and 0V reference), may not match what is configured. Your package indicates Sensor 5 0V A is configured for both Pedal Main/Tracking as well as Throttle Position Main/Tracking. Are you sure these sensors are wired to the correct 5V and 0V pins?

Your logging rate is insufficient to give you more than an indications that "something happened". If you really want to debug this, you will need to have level 2 logging and set these specific sensor and diagnostics channels to log at say 20 - 50 hz.

I am concerned that you have two different position sensors for main & tracking. There will always be some hysteresis in the linkage (less when new for sure) so it will be challenging to keep these in sync. Ideal would be a dual output hall-effect pot on the throttle bodies. The M1 requires the main & tracking sensors to remain in sync, there is a table "Throttle Servo Bank 1 Position Sensor Tracking Linearisation" that may help you handle any non-linear behavior in the linkage.

I haven't looked at your log but David has a lot more experience than me when it comes to analyzing data with I2.

One thing I can say for sure is that we had issues in the past with a Jenvey DBW that kind of works the same way as yours when it was starting to heat soak in the engine bay. I am suggesting this as you mentioned this happened after a few laps around the track.

Our solution to our tracking fault problem was to increase the airflow around the dbw to help it cool it down. We did not see the fault happening after. Might be worth a shot to try it.

Perfect thanks for your help again.

We have got level 2 logging so I will check these things next time we out racing and will let you know.

Did you resolve this? Could it be the result of a wonky pedal position sensor?

Interested in your PID settings for the S54 DBW. I have a couple of different configurations that I have used.

--Peter

I recently worked on a car using the S54 DBW Servo and a push-pull cable to ITB linkage. Getting the "Tracking Linearisation" correct was the critical factor in making this work. In our case, we used the sensor on the throttle bodies as the Main, and the sensor on the servo as the Tracking. This allowed the engine calibration that had been done with the cable throttle to be used without changes. But did make the PID turning a bit challenging due to the hysteresis and backlash in the system.

This is an issue that i have seen before with these sorts of installations. The sensors get out of sync as one is on the motor and the other is at the end of a number of shafts and linkages. The thermal expansion and basic vibration of the engine make the two values stop tracking together, the M1 detects this as a fault in the DBW and shuts it down. When the driver gets off of the throttle pedal, the servo resets and keeps working until this occurs again.

The solution to it is to use the sensors on the motor only, and not use a sensor on the butterflies.