I think I have got this RPM hang issue figured out. Just can't fix it quite yet. If it's possible to control some of the idle logic in the ecu, I think i could fix the issue. When traveling at low speeds, like in a parking lot or stuck in traffic. Sometimes a blip of the throttle will cause the RPM's to rise. I noticed that it doesn't happen when you come to a stop or you are in neutral. This morning I decided to do a little datalogging to see whats going on.
I did some logging and it appears that while the car is not moving or possibly traveling below 2 KM/H. The cars idle throttle opening angle is set to about 3 degrees regardless of engine speed. This behavior is much different when the vehicle is moving.
I did some datalogging today. I ran the car up to about 5000 rpm in first gear and lifted the throttle. This was to see what throttle angle the ecu would choose at different engine speeds and scenarios. I tried this with 3 scenarios.
1. disengaging the clutch and putting the car in neutral.
2. disengaging the clutch and leaving it in gear.
3. keeping the clutch engaged and the car in gear.
The data came out pretty much the same for leaving the car in gear regardless of what the clutch was doing. The difference came when the car was in neutral. When the car was in neutral the ecu chose a smaller throttle angle. I did my best to line up the data here by RPM. I have the raw datalog below.
It will take more of the ecu's logic to be defined to fix this issue but if we could adjust the throttle angle while the car is in gear to be like the throttle angle when the car is out of gear. I think this particular RPM hang will go away. We potentially could also use these same tables to allow the throttle to close more at higher RPM's to allow the engine to wind down faster. This could help for smoother gear engagement during quick up shifts and possibly reduce strain on the gears in the transmission.
I posted this information here in hopes that some of the ecu's logic could be reveled and we could fix this issue.
