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Alex B

Force closed loop idle lockout on AP% and a few other E-throttle questions

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Quick summary of my setup:

  • Volvo 2.8l I-6 with E46 M3 individual throttle bodies
  • E46 M3 three-wire IAC valve
  • E-throttle actuator from a BMW S85 

Idle Control Question:

To get smooth tip-in and tip-out I am blending idle valve airflow before the throttle plates open with a 3D idle base position table, see relevant tables below:

 29634050_ISCtable.png.dfb80e13abea108c4c28b5588f4a6219.png

2129449338_ethrottletarget.png.a104da4306fc7a09c0fee7d092266bbb.png

 

This works really well and I am overall very happy with the low-speed driveability. The issue is I can't get the ECU to jump out of closed loop idle control properly so I'm forced to run open loop. Since I have idle control with a solenoid valve the "AP/TP Lockout %" seems hard coded to TP%. If I switch on closed loop idle it will control idle great, but I can sit in the car and pump the pedal to my hearts content from 0-5% AP and get no change in idle valve position, effectively nulling the tip-in and tip-out smoothness I get from the 3d base position table. Is there a way force the ECU to jump out of closed loop on AP% while using a solenoid valve?

 

E-throttle questions:

Are there any plans to add a feed forward table to the E-throttle control? A way of doing gain scheduling would also be extremely useful, even if it's just different PID parameters for opening and closing the throttle. Sometimes just one set of P, I, and D terms doesn't work out quite as well as I'd like, especially with the lack of a feed-forward table.

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3 hours ago, Alex B said:

This works really well and I am overall very happy with the low-speed driveability. The issue is I can't get the ECU to jump out of closed loop idle control properly so I'm forced to run open loop. Since I have idle control with a solenoid valve the "AP/TP Lockout %" seems hard coded to TP%. If I switch on closed loop idle it will control idle great, but I can sit in the car and pump the pedal to my hearts content from 0-5% AP and get no change in idle valve position, effectively nulling the tip-in and tip-out smoothness I get from the 3d base position table. Is there a way force the ECU to jump out of closed loop on AP% while using a solenoid valve?

You are right, I would have expected like you that AP should be used as the lockout when there is E-throttle in the system - even if the idle control is not via DBW.  I just tested on the bench and found the same as you.  So I suspect this is an oversight that no one has noticed before.  I will get it logged as an issue to get it on the list of things to look at.

 

3 hours ago, Alex B said:

Are there any plans to add a feed forward table to the E-throttle control? A way of doing gain scheduling would also be extremely useful, even if it's just different PID parameters for opening and closing the throttle. Sometimes just one set of P, I, and D terms doesn't work out quite as well as I'd like, especially with the lack of a feed-forward table.

Not likely to be such a major change added in G4+.   If it was requested enough in G4X it might be considered but I havent personally come across a need for it yet, I have always been able to get adequate control with just the 1 set of PID and fixed feed forward.

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14 hours ago, Adamw said:

You are right, I would have expected like you that AP should be used as the lockout when there is E-throttle in the system - even if the idle control is not via DBW.  I just tested on the bench and found the same as you.  So I suspect this is an oversight that no one has noticed before.  I will get it logged as an issue to get it on the list of things to look at.

 

Not likely to be such a major change added in G4+.   If it was requested enough in G4X it might be considered but I havent personally come across a need for it yet, I have always been able to get adequate control with just the 1 set of PID and fixed feed forward.

Adam, Thanks for verifying and getting it on the list. Fingers crossed it gets addressed. Ignition idle control helps but I still get hunting idle in some situations.

Understood on the e-throttle stuff.

 

11 hours ago, Brad Burnett said:

Just curious as to why use the IAC valve and not the DBW system to control the idle?

I tried doing this at first but the control was not fine enough. I had to run very retarded timing at idle to limit engine torque and this ended up pushing idle exhaust gas temperature higher than i was comfortable with. I drive the car on the street mostly and sit in traffic on hot days. Apart from the closed loop idle issue the setup has worked extremely well.

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12 hours ago, Alex B said:

I tried doing this at first but the control was not fine enough. I had to run very retarded timing at idle to limit engine torque and this ended up pushing idle exhaust gas temperature higher than i was comfortable with. I drive the car on the street mostly and sit in traffic on hot days. Apart from the closed loop idle issue the setup has worked extremely well.

Understood.  Im sure there may have been a way to sort that out, but I do understand there are many solutions to most problems and not all of them are wrong.

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