ECMlink AFREst "spike"

[EvilTSi_97]

Hello,

Craig and I decided to drop his 1250 BlueMax injectors into my car tonight. We got the idle where we want it to be. I'll be doing some cruising around for mid-range tuning tomorrow. I really want to understand more of what's going on...and even more importantly...why. I noticed that my AFREst seems to have a "spike" to it. The only connection I can see is that each time the O2 is reading on the high end. We have also put in Sam's "drop in" VE table: http://www.dsmtuners.com/forums/tuning-engine-management/409538-ve-dip.html#post152666631

With that in there, we ran CombinedFT on the VE table for idle and got the WB at an acceptable value. My question is this: why is AFREst off, and then it has a spike where it's darn near matching the WB reading? If you notice the first spike, it goes from 13.9 to 14.7...while the WB reading stays the exact same at 14.9.

Thanks so much for any input!

 

[LiquidX]

I will let you in on some important information. When locking in open loop, the ECU pulls a percentage of fuel so you won't be sitting at a 14.7 ratio. When adjusting your deadtime and what not to match the the AFREst, you actually need to set it to what the AFREst is, not at 14.7:1 like you have.

You should have access to the Link forums so review this thread I started on there, start at post #8
ECMTuning User Support Forums

This may have some helpful information as well. It's a discussion Craig and myself had last month.
http://www.dsmtuners.com/forums/tun...-locking-open-loop-wideband-switch-point.html

 

[EvilTSi_97]

I will let you in on some important information. When locking in open loop, the ECU pulls a percentage of fuel so you won't be sitting at a 14.7 ratio. When adjusting your deadtime and what not to match the the AFREst, you actually need to set it to what the AFREst is, not at 14.7:1 like you have.

You should have access to the Link forums so review this thread I started on there, start at post #8
ECMTuning User Support Forums

This may have some helpful information as well. It's a discussion Craig and myself had last month.
http://www.dsmtuners.com/forums/tun...-locking-open-loop-wideband-switch-point.html

Thank you for sharing that! Why does the ECU pull fuel so it's not hitting the target AFR? I always assumed that in open loop, the ECU looks up what's in the DA table and aims for that AFR. So, it seems like I may have done the idle tuning backwards? For example, instead of tuning for 14.7, I should be tuning for what AFREst is hovering around?

With that said, do you see the little spikes I am talking about? What is going on there inside the ECU? I can't seem to trace anything that would merit a change.

I do see what Craig is talking about, but am not really understanding everything. This may be something I have to call him about, but I am assuming you made the changes, too So this "spike" has something to do with needing a little airflow smoothing? I think I am confused on what needs to be changed in the DA table to 10.5% that he is referencing there. I know there is the Airflowsmoothing tab in the DA tables, but my values are as follows:

IdleAirSmoothing: 75%
OffIdleAirflowSmoothing: 87.9% across the board.

2. You should be able to eliminate the spikes on the AFRatioEst by adding a little airflow smoothing. Change the DA table to something like 10.5% for idle, and then 10.5% up to 2000rpm, and 25% or so above that....then uncheck the "Disable airflow smoothing with SD" box on the Misc tab. You'll have to play around with the values a bit to get the best response and drivability.