AFX issues exhaust leak?

[383]

Im trying to tune with a NGK AFX in the sens1 bank 2 port of my LG super pros but it keeps reading 16.00 until i get to about 2~2500rpm then it seems to read normal. The weird part is that if the car is rolling 40+mph it reads 11.0~10.8.
I know the tune is not that far off. No knock, idle seems fine. I tried to adjust the EOI timing -20* twice but no change.
I originally thought I had a toasted 02 sensor from a misfire(unplugged coils) so I got a new sensor but more of the same.
So now Im thinking exhaust leak, has anyone else had this issue? I have foil tape under the clamp on the header and the cat delete pipe.
2007 Z06 cammotion 232/242 118 halltech intake catless LG super pro 1.7/8" milled heads .040 /12:1 93 octane E10
Im going to try to seal up the exhaust some more rinse and repeat....

[GHuggins]

I've got the same problem right now on our ZL1 because of long tubes and no cats. It's just a time change needed with the O2 sensors. Under Fuel, Open - Closed Loop, Closed Loop Integrator and possibly the Closed Loop Proportional Airflow settings. Just keep increasing "mainly integral" until your O2's begin switching correctly again on both banks. I've been told this is what will fix it. Haven't gotten around to being able to verify it yet. Been busy with other tuning.

Give it a try and see if this helps.

[383]

Thanks, I ended up finding multiple leaks in the cat delete pipes slip fittings. That and it was a little lean under 2200rpm. It seems to be acting fine in the limited driving I could do today.

[ingsteve]

try eoi vs ect +15* on the whole table and let me know about the drivability. My ls2 g5x1 is like stock with this change (not only this of course but this was night and day difference).

[383]

try eoi vs ect +15* on the whole table and let me know about the drivability. My ls2 g5x1 is like stock with this change (not only this of course but this was night and day difference).

I did 20* I wish there was something I could log to figure out how much to move EOI exactly

[ingsteve]

you said -20*...i said +15* on the whole table. Completely different scenario...please doublecheck.

[383]

I wanted the EOI later to give the exhaust valve more time to close before sending fuel out the exhaust and looking lean on my WB

[schpenxel]

I wanted the EOI later to give the exhaust valve more time to close before sending fuel out the exhaust and looking lean on my WB

So do you add or subtract in the boundary table to make this happen?

[383]

So do you add or subtract in the boundary table to make this happen?

You have to look at the trend. Some are setup different GM sets the EOI later when warmed up so you can adjust the whole table towards the hot side. You can adjust till the wb stops getting richer, then you know your not spitting unburnt fuel out the exhaust. You should probably do this before you finish your ve or maf fueling.

[ingsteve]

i think you can try adding and let us know....

[383]

i think you can try adding and let us know....

i I have the flu right now but ll try both this weekend and let you know

[383]

i think you can try adding and let us know....

Ok I did try to add but it seemed to get a bit leaner so I went back. Now when Im tuning ve and I log a drive every cell is between 2~3% but if I log while idling and revving a little in neutral it reads 9~10% lean... why is that? Adjusting the EOI does not seem to help the situation. Could the exhaust still be leaking a little?

[schpenxel]

Ok I did try to add but it seemed to get a bit leaner so I went back. Now when Im tuning ve and I log a drive every cell is between 2~3% but if I log while idling and revving a little in neutral it reads 9~10% lean... why is that? Adjusting the EOI does not seem to help the situation. Could the exhaust still be leaking a little?

Transient fueling plays a role when revving like that. That would be my guess on what you're seeing. If in steady state operation you're still down in the 2-3% range, then that is fine for MAF/VE tuning.

If you do a graph and put commanded lambda (or AFR) and actual wideband lambda (or AFR) on the same graph, you'll probably see what I mean. When you hit the gas it will go rich or lean then when you let off it will do it too. Transient fueling is REALLY hard to get right IMO, and most don't ever even bother. I tried but gave up

[383]

I meant to say when i rev and hold it stays lean, Im aware of transient fuel and I try to stay as steady as possible. It seams that the load of driving gets me where I want to be but I cant see that on a log just idling...
I just want to make sure Im not missing something before I start doing WOT logs
Thanks for the replies

[schpenxel]

I meant to say when i rev and hold it stays lean, Im aware of transient fuel and I try to stay as steady as possible. It seams that the load of driving gets me where I want to be but I cant see that on a log just idling...
I just want to make sure Im not missing something before I start doing WOT logs
Thanks for the replies

You sure you have good injector data?

[383]

Yup. Stock.

[GHuggins]

Try adding back to the injector timing - "raising the boundary". Side effect of this is running a touch lean at idle, but not much more. The oposite as you've seen, makes it run more rich at idle - thus making one think it's the best way to go. You'll really notice the gains when your under load after you retard the injection timing - she'll go pig rich now and require a lot of fuel to be taken back out... Really big benefits with turbos or cams. You've got degrees as the representation in your ecm for injection timing I believe, so add 12 to 15. After that it typically goes the other way again unless you have a pretty radical cam. Then it's a good rule of thumb to start around a 20 degree addition.

[383]

Try adding back to the injector timing - "raising the boundary". Side effect of this is running a touch lean at idle, but not much more. The oposite as you've seen, makes it run more rich at idle - thus making one think it's the best way to go. You'll really notice the gains when your under load after you retard the injection timing - she'll go pig rich now and require a lot of fuel to be taken back out... Really big benefits with turbos or cams. You've got degrees as the representation in your ecm for injection timing I believe, so add 12 to 15. After that it typically goes the other way again unless you have a pretty radical cam. Then it's a good rule of thumb to start around a 20 degree addition.

Im real lean at low load and idle, I wasn't able to fatten it up yet. when I added to the EOI it got a touch leaner. Ill try to go to +12 tomorrow. maybe the -20 overshot and made it worse?
How can it be so lean in neutral and so close while driving?

[GHuggins]

Engine Load - Maf or VE a little off? Try "adding" to the injection timing boundary only and set your other injection tables back to stock... This really tends to help with throttle transitions even though I know you don't seem to have that typical kind of problem, but you did adjust it one way to cause these problems or is it you have been trying to fix this one issue all along?

[GHuggins]

Come to think of it when I was starting out I had this same issue with a cammed vette. I went about it in a wrong way by setting stoich rather rich "high 13's" then readjusting MAF to keep the fueling right to get rid of some horrible bucking the car was having. At light throttle and idle it was running 15.1 to 15.5 AF. After doing the stoich and MAF "the way that is wrong", I wound up getting rid of all bucking and running at a constant perfect 14.6 to 14.7 AF. I only learned later to adjust injection timing to do the same thing the correct and non fuel wasted way...

SO set your injection timng by adding to the boundary, then recheck...