OL tuning

[Zick]

How lean can I safely go during cruise? I'm trying to tweak my Open loop table for better mileage but don't want to melt a piston in the process.

Once I get set into OL permanently, is there anything else I should be looking at tweaking?

[Zick]

While looking at a log from today I noticed something weird. Why does it look like my O2 sensors are turning back on for short periods and causing my AFR to go back to stoich? Seems to happens usually around idle or parked.

[Russ K]

Looking at your histograms, the LTFT & STFT are 0 so your in open loop.
Are your O2 sensors still plugged in?
16.0 - 17.0+ AFR is getting lean.

Russ Kemp

[Russ K]

Take a look at your open loop fa vs temp vs map tables. To have a 14.7 commanded afr, you need the value of 1 at operating temps (14.7/1 = 14.7)
Of course you would need to be richer for cold starts.
A value of .90 is 16.33 afr !

Russ K

[Zick]

Looking at your histograms, the LTFT & STFT are 0 so your in open loop.
Are your O2 sensors still plugged in?
16.0 - 17.0+ AFR is getting lean.
Russ Kemp

O2s are still plugged in, and I have my WB wired in acting as a NB as well so I cannot unplug that one.
I have it set for between .90 - .95 once it hits operating temps.

Take a look at your open loop fa vs temp vs map tables. To have a 14.7 commanded afr, you need the value of 1 at operating temps (14.7/1 = 14.7)
Of course you would need to be richer for cold starts.
A value of .90 is 16.33 afr !
Russ K

I realize how to figure all that out already. I've only modified my OL F/A table when the engine temp gets up to operating condition and then I leaned out that area. The rest is stock, so its still rich when cold.



What I'm trying to figure out is why when I'm in gear and say at a stop sign not moving, why does my AFR go rich to 13.7-14.7. I have it set for .95-.90 at operating temp and idle Kpa, but for whatever reason it is dumping more fuel than it should.

[Russ K]

Just checked the scan data again, your open loop fa multi table values mostly match the commanded afr as scanned. Yes at certain map/coolant temps your commanding 14.68, but the wide band is not. If you want say a 16.0 afr, fill the table areas with .9175 at all maps from 176 & up ect. Then use the afr % error on the histogram to set your ve table.

Russ Kemp

[EC_Tune]

Just checked the scan data again, your open loop fa multi table values mostly match the commanded afr as scanned. Yes at certain map/coolant temps your commanding 14.68, but the wide band is not. If you want say a 16.0 afr, fill the table areas with .9175 at all maps from 176 & up ect. Then use the afr % error on the histogram to set your ve table.

Russ Kemp

Russ,
The only problem is that the system will pick the *richest* AFR between Stoich and OLAFR. So the leanest you can actually go is stoich.

If you plan on going back into closed loop Stoich is the leanest you will go.

EC

[Zick]

Just checked the scan data again, your open loop fa multi table values mostly match the commanded afr as scanned. Yes at certain map/coolant temps your commanding 14.68, but the wide band is not. If you want say a 16.0 afr, fill the table areas with .9175 at all maps from 176 & up ect. Then use the afr % error on the histogram to set your ve table.

Russ Kemp

Ok, for example; this is while in gear and stopped.
Temp = 192
MAP = 46
OL F/A = .90

this condition I am seeing 14 AFR.

So if I understand you correctly, your saying that my VE table is off at that spot and needs to be adjusted?
Still, why are my O2 sensors kicking on at this moment too?

[Zick]

Russ,
The only problem is that the system will pick the *richest* AFR between Stoich and OLAFR. So the leanest you can actually go is stoich.

If you plan on going back into closed loop Stoich is the leanest you will go.

EC

Well right now, its going richer than stoich cause I'm seeing around 13.8 - 14.3 while in gear and idling.
Also, if I can get this problem fixed I probably won't be going back to Closed loop ever.

[Russ K]

Ok, for example; this is while in gear and stopped.
Temp = 192
MAP = 46
OL F/A = .90

this condition I am seeing 14 AFR.

So if I understand you correctly, your saying that my VE table is off at that spot and needs to be adjusted?
Still, why are my O2 sensors kicking on at this moment too?

Your commanded afr varies by map, thats why I would set the OLFA table to .9175 at all maps from 176F and warmer. Then log your commanded afr, it should then stay at 16.0 from 176F and warmer.
If it does, use the afr % error histogram and copy & paste the error % to the ve table. Make sure dfco is disabled first.
The O2 sensors will still report mv when in open loop, the pcm will just ignore them.

Russ Kemp

[Zick]

Your commanded afr varies by map, thats why I would set the OLFA table to .9175 at all maps from 176F and warmer. Then log your commanded afr, it should then stay at 16.0 from 176F and warmer.
If it does, use the afr % error histogram and copy & paste the error % to the ve table. Make sure dfco is disabled first.
The O2 sensors will still report mv when in open loop, the pcm will just ignore them.

Russ Kemp

Ok, I have everything from 176-212 temp and 20-65Kpa set at .90-.95
I did not set adjust anything higher than 65Kpa because I don't want to lean it out under load.
So far when logging I see that the Commanded AFR is reading correctly until I come to a stop light. As soon as I come to a stop, my commanded AFR goes back to Stoich. Why is it doing this? I am in the Map and Temp to be commanding leaner but its ignoring this.
I realize that usually the PCM goes for whatever is richer but why does it only do this when stopped and not while moving?

[Russ K]

I just noticed that you need to copy your open loop fa table to the open loop alcohol fa table. The help file says this table is used for flexible fuel capable calibrations only. I would give it a try.

Russ Kemp

[Zick]

I just noticed that you need to copy your open loop fa table to the open loop alcohol fa table. The help file says this table is used for flexible fuel capable calibrations only. I would give it a try.

Russ Kemp

Hmmm, didn't think that would be getting used but I'll give it a shot. I can't think of any other table that would be getting used during idle except for the OL F/A table.
I'll report back.

[Zick]

Coping that table has helped stabalize my AFR at least, but something is still causing my idle to go back to Stoich.
But running like this I've been getting pretty good gas mileage.