EGO oscillations

[AVP]

I was looking through some logs and noticed that whenever i go off throttle i have my mixture going really rich for a few events, until EGO brings it back to normal. My fadeout time on accel enrichment is 0.27sec but i dont think that has anything to do with it.

Also my accel enrichments are borderline lean, which is fine i guess so long as the car drives ok.

Then i noticed this from the help files:

EGO kpa enable: use more than 32-40kpa.  I used to have that at 27 on megatune and it helped there. Now on vemstune it is recommended that its above 40kpa. What does this setup refer to or do?

Also engine cycles before enabling EGO: i have 2 although it is recommended to have 10 to avoid oscillations.
I was under the impression that if the VE table is well made, then if i had the EGO making fast corrections it would make things easier since the VE is ok. How many secs is 10 engine cycles, and should the EGO be at 10cycles definitevly to avoid oscillations, or should i gradually increase it until any oscillations are deminished?

[gunni]

Going rich fpr a few events is normall, look at your pulsewidth and see how long it takes from the pulsewidth going to zero and how how long the mixture goes very lean, that will tell you the lag of your mixture readings.

[AVP]

from a brief look, an example:

from overrun, and lamda 1.29, it takes about 1.5sec to go fromlean to target lamda after the throttle has been pressed.

Then another example:

from overrun to neutral:

as revs go towards my idle speed, lamda gets from lean to my idle lamda (1.02), but then as the revs reach the idle speed this happens:

lamda goes rich up to 0.84 then climbs back up to 1.02 and the whole thing takes: 4secs!!!

[GintsK]

Then i noticed this from the help files:

EGO kpa enable: use more than 32-40kpa.  I used to have that at 27 on megatune and it helped there. Now on vemstune it is recommended that its above 40kpa. What does this setup refer to or do?

Sorry! where you found this?? It is stupid suggestion (about >40kpa)! Normally mixture is stable if you configure this value few kpa (like 5...10) lower than you see at idle. Together with fuel resume at 1500...1700rpms what gives time to rebuild fuel film in ports before rpm drops to idle.

Gints
What vemstune version?

[GintsK]

regarding Ego correction delay - just find lower value where no stupid behaviour. Beside VE table there is some inertia phenomenons with fuel film. If you was at WOT and rapidly goes to idle - there is still huge amount of fuel in ports and combustion chamber. At this situation it takes some time to stabilize condition. And egoc on just makes everything worse at this time.

[AVP]

its my mistake,
it is not kpa but kp

on the EGO settings it says Ego Speed (PID speed) kp, and the F1 (Help) recommends above 32, usually around 40

i was using 27 on that.

using 1.1.88 and feb 21st vemstune

i changed the speed WBO2 to 34 and the cycles to correction to 3 instead of 2. It seems to be a bit better.
If i use cycles 10, then it takes a lot longer to go from rich to normal idle lamda when going to neutral.

[GintsK]

from a brief look, an example:

from overrun, and lamda 1.29, it takes about 1.5sec to go fromlean to target lamda after the throttle has been pressed.

Then another example:

from overrun to neutral:

as revs go towards my idle speed, lamda gets from lean to my idle lamda (1.02), but then as the revs reach the idle speed this happens:

lamda goes rich up to 0.84 then climbs back up to 1.02 and the whole thing takes: 4secs!!!

Can you ilustrate it with log file?
 you are not happy with slow egoC, then try also speed limit higher - somewhat like 65.

[AVP]

ah i see
so the higher the speed limit, the faster the reaction of the EGO?

wont that induce more oscillations though?

[GintsK]

How to say...more rapid reactions. And of coarse at some combination with too low delay it will cause oscillations.

[AVP]

I see. I'll do some more logs. Took it to 40 as recommended now!

[tweak]

How many engine cycles before aplying correction do you guys use?

I'm running at 20 cycles, which could be a bit too long.. The idea is of course to let the condition settle before aplying any further adjustment. It's passing a turbo charger before the EGO sensor so it should be figurable out from distanse from the sylinder how many cycles you need.