What fuel mixture do I want and how?

[sdhager]

I am working on a 98 Firebird LS1 with auto trans. I have my VE table dialed in, and am working on the MAF table since the BENs are different with it plugged in vs SD mode. After I get it dialed in, what fuel trims do I want to shoot for. Currently I am running about 11.5 AFR at WOT. Is this too rich? I was thinking something along the lines of 12.5 or 12.8. What do you guys think? Is there a chart somewhere that I can use to determine the best AFR?

Also, where do I go to change the desired AFR above 4k rpm?

I also noticed that this car runs about 17-18 afr during cold startup, but seems to run OK. Is this possible? I have disconnected the air pump relay and still get the same thing. Will it even run OK at that AFR or do I have another problem? If it can run, then what do I need to adjust?

[sdhager]

I am working on a 98 Firebird LS1 with auto trans. I have my VE table dialed in, and am working on the MAF table since the BENs are different with it plugged in vs SD mode. After I get it dialed in, what fuel trims do I want to shoot for. Currently I am running about 11.5 AFR at WOT. Is this too rich? I was thinking something along the lines of 12.5 or 12.8. What do you guys think? Is there a chart somewhere that I can use to determine the best AFR?

Also, where do I go to change the desired AFR above 4k rpm?

I also noticed that this car runs about 17-18 afr during cold startup, but seems to run OK. Is this possible? I have disconnected the air pump relay and still get the same thing. Will it even run OK at that AFR or do I have another problem? If it can run, then what do I need to adjust?

I guess nobody seen this, or else noone knows. I fixed my WOT problem by disabling Cat Protection. I am now running close to 12.3 afr WOT.

Haven't addressed the cold problem yet.

[mr.prick]

You can richen up cold start by decreasing B3605

[sdhager]

You can richen up cold start by decreasing B3605

What mixture do I want to shoot for when cold?

What about WOT?

Any idea why I have to disable cat converter protection to fix my WOT mixtures?

Thanks.

[joecar]

Yes, sometimes a post gets missed... sorry about that.

COTP provides it's own extra fuel which is not accounted for in the AFR pid.

For WOT, set B3605 and B3618 (if you're using PE) to something like 12.6-12.8 and see how you go... watch for ping...

Since you have VE table corrected, in SD your actual AFR will match your commanded AFR.
With the MAF, the same is true if your MAF (and also all your injector tables) is correct also.

B3605 row's are indexed by ECT, pay attention to which row you're changing.

Use scantool->tunetool linking to highlight cells in B3605.

[mr.prick]

What mixture do I want to shoot for when cold?

What about WOT?

Any idea why I have to disable cat converter protection to fix my WOT mixtures?

Thanks.

Newer OS' are set at 14.63,
anything that will get you richer than what you are running at cold start will do.
Tuning the OLFA table
GM.AFR may read richer than you actually at first but
it's better than starting up 17+AFR.
Try adding XX% at first so you can get to op temp.

[The Alchemist]

Probably reversion in your tail pipe if thats were you have your wideband mounted. Makes the AFR look leaner than it really is.....to confirm lightly touch the throttle to lift the revs to 1200rpm or so...if the AFR suddenly comes right then thats your "problem"...ie: not really a problem at all.....

[sdhager]

Probably reversion in your tail pipe if thats were you have your wideband mounted. Makes the AFR look leaner than it really is.....to confirm lightly touch the throttle to lift the revs to 1200rpm or so...if the AFR suddenly comes right then thats your "problem"...ie: not really a problem at all.....

It is mounted pre-cat bolted in the side of the exhaust pipe. Is there reversion there? It works OK closed loop as far as fuel trims are concerned.

[The Alchemist]

It is mounted pre-cat bolted in the side of the exhaust pipe. Is there reversion there? It works OK closed loop as far as fuel trims are concerned.

Ahhh cancel that, I wasn't sure where you had it positioned mate.....
Is your engine bog standard in the cam department? A bit of extra overlap during cold start up can push extra unburnt Oxygen into the exhuast making the wideband look "lean" but it isn't really.....If the engine runs OK I wouldn't worry about it.
MIke

[sdhager]

Ahhh cancel that, I wasn't sure where you had it positioned mate.....
Is your engine bog standard in the cam department? A bit of extra overlap during cold start up can push extra unburnt Oxygen into the exhuast making the wideband look "lean" but it isn't really.....If the engine runs OK I wouldn't worry about it.
MIke

I'm not sure what you mean about the bog being standard in the cam department. I don't experience any bog, and it feels like it runs OK, but as soon as closed loop activates the AFR comes in line.

I guess I need to graph closed loop and AFR just to be sure.

I just don't understand why the lean cold start, unless it really is lean. If I only knew if they would actually run with an AFR as high as 17-18, then I would know if it was possible or not. I have to believe my wideband, I don't have anything else. Also, my wideband brings my fuel trims into +-2%, so it must be pretty close. This is the only car I have used it on as this is my first tune.