Idle settings

[T40]

Hello

Went from 1.0.73 to 1.1.44 and now i have some ilde controller issues.
Integral deadband and IAC deadband doesn't seem to work in new firmware.

With 1.0.73, IAC reference point was set according to 900rpm, idle target was 700rpm and iac deadband 255rpm. After throttle pedal release, rpm softly decreased from 900 to 700.
With 1.1.44 i can't achieve same result. To get proper idle rpm, i have to set reference point according to target rpm, but then rpm momentarily drops below target after throttle release.

Ideas?

The car is bmw with m50 engine.

Edit:
Perhaps i expressed poorly, but this is what i meant:
http://www.vems.hu/wiki/index.php?page=GenBoard%2FUnderDevelopment%2FAlphaNIAC
When releasing the throttle at high rpm the controller will think that the idle is very high and it will fully close the idle motor. We need to prevent that.

Is there solution for that when using newer firmwares like 1.1.44 and 1.1.47?

[rob@vems.co.uk]

I'd love to give you an answer but I don't have access to anything running a VEMS at the moment.

[GintsK]

I never used big dead band. If it is real dead band controller leaves IAC as is.
For smoother action I use very high D settings. P and I is much more sensitive than D for some reason. Usually 20-40 for P, 10-22 for I and 100-255 for D.
I also found that fluctuating can be caused from aggressive Ego correction after deceleration event.

Gints

[T40]

This is how i understand the iac deadband works in 1.0.73:

IAC deadband (rpm) value is IAC activation point above target rpm.
For example:
Idle target: 700rpm
Iac ref pos: 40
IAC deadband: 255
When throttle is released at high rpm, IAC position stays at 40 until rpm drops down to 955 (700+255). Then IAC position slowly decreases, until 700rpm is reached (at IAC position 32).

Did i miss something?

[GintsK]

Hm. There is lot unsorted [missing] information about all these things. Where you find information about slow closing when deadband active? Are deadband means 700 +/-255 or +255 or +/-128 from target?
I using low deadband settings  - about 20rpm. And almost everything can achieve good settle to idling. Exception was long traffic jams in hot weather when IACV reference must be higher. But in newer versions reference value can be adjusted against IAT. High D value and right I decrease limit helps a lot. Other thing to watch is AFR and ego correction during engine deceleration.

Gints

[T40]

The engine has kind of character that it wants to stall after deceleration. I can't find out why. Ego correction is off.

Hm. There is lot unsorted [missing] information about all these things. Where you find information about slow closing when deadband active?

Neither i have found any good information about this, just writing from my experience.
At IAC deadband 255, slow closing worked even if P, I and D fields were filled with 0.
Seems that IAC deadband does its job independently.
These are my last 1.0.73 settings. P is 100 only because it helps to quickly open IAC when sudden rpm drop below target occurs.

Now, lets return to 1.1.44/1.1.47.
I did some experiments. No matter what the value of IAC deadband is, it doesn't make any difference. Also Integral deadband doesn't seem to work. When trying with PID, this happens:

When releasing the throttle at high rpm the controller will think that the idle is very high and it will fully close the idle motor.

[MWfire]

IAC deadband doesn't exits in 1.1.47.
If targer rpm minus current rpm is greater then integral_deadband than integra pid do correction. If not integral pid correction is zero.
Try set overun_fuelresume to 1100-1200.

[Sprocket]

Lots and lots of things need a little explanation where idle settings are concerned I will be posting up shortly asking those questions

As for stumbling on over run aproaching idle, I found it more of a problem with Alpha N where the VE numbers in the lowest row needed to be knocked right back. The deep vacuum on over run needs far far less fuel. I had EGO turned on and it was removing fuel, but when the engine speed aproached idle, EGO could not respond fast enough to put the fuel back in. Was easy to spot with logs and the fix was just as easy.

Do you have any logs of these over run events that you can look at what the Lambda is doing?

What are your over run fuel cut settings? What about fuel cut under kpa? does your engine draw huge vacuum on over run?

Other things to consider is adding a large advance ramp in the lowest RPM column, say 30 degrees around the row where your idle sits on the table. This will help when the rpm takes a dive below idle set point.


I had stalling issues on over run when i was using 1.0.53 on the 1400 engine. I upgraded to 1.0.73 and those problems almost disapeared, but the main problem is not knowing what the numbers in the settings actualy mean. You end up changing a number and if it makes an improvemnt, you go with it, not really knowing what you have done or why!!

[T40]

Maybe i underestimated VE lowest row influence to overrun idle approach, i haven't spent time experimenting with that. (in case of 1.0.73 i didn't need to)
Overrun fuelcut was not in use.
Other questions i can't answer right now, my attention was aimed at IAC behavior.

Anyway, i got ideas and directions to continue. Thanks a lot.

[T40]

Tried several settings, no improvement.
Here are my logs:
log001.xls
(ignition based idle control disabled, EGO correction off, IAC at constant position (idle 900rpm), overrun fuelcut off)
log002.xls
(IAC at constant position (idle 800rpm), overrun fuelresume 800rpm)

[MWfire]

Try set fuelresume to 1100 or 1200
Set ref pwm that when you relase throttle rmp drops to 1000. Set decrease integral limiti to 20-40.

[T40]

Try set fuelresume to 1100 or 1200

Overrun fuelresume makes no difference.

Set ref pwm that when you relase throttle rmp drops to 1000. Set decrease integral limiti to 20-40.

That doesn't work if rpm drops to idle after long time overrun.

I took 1.0.73 into use again. Now there is no problem even if idle target is very low.
I wish that newer firmwares had feature like this .
http://www.youtube.com/watch?v=qhNY9F2ctGw&feature=channel_page