Closed loop... commandable?

[12_Square]

Is closed loop always stoichisometric…? I thought open loop commanded fueling sets the target points for closed loop. Is that wrong?

The reason I’m asking is because my wideband shows that my engine is running 0.99 - 1.01 lambda in all conditions, except before closed loop begins, and also in PE mode (where it’s 0.80 lambda, as expected).

Maybe I’ve overlooked something? Just trying to understand how everything works together now before I start turning things off.

(‘98 Trans Am)

[5.7ute]

Closed loop is always at stoich, because that is what a narrowband sensor switches around. Lambda 1.0.
Open loop commanded AFR is just that. The AFR that you want at certain engine speeds & temps until closed loop is enabled.

[12_Square]

Hmm… if only it could be better than that.

So now I have it in open loop, but when I run a scan, I’m still seeing LTFT adjustments. How can that be? This is what I’ve done so far:

- Closed loop temp enable: 140 C
- O2 with open loop commanded fuel {B4206}: Disabled
- Long term fuel trim correction {B3801}: Disabled
- Minimum coolant temp to enable LTFT {B3802}: 139 C
- STFT idle enable {B4108}: Disabled

What am I missing?

[joecar]

Post some logs.

[joecar]

Some clues may or may not be found in post #4 here: Summary-Notes (http://forum.efilive.com/showthread.php?14188-Summary-Notes)

[12_Square]

Here’s a quick log. I’ve never had it in open loop before so I set commanded fuel at EQUIV 1.10 and dropped the timing just to be in the clear. LTFTs should be 0 though...

On another note,
What does {B4206} “Use O2 With Open Loop Commanded Fuel Table” do, if stock sensors only operate around lambda 1.00?


16361

[joecar]

B4206:

in OL, uses STFT's to trim on cells in B3605 that are stoich (Lambda 1.00)... for cells that are not stoich, there is no trimming.

[5.7ute]

Did you clear all the LTFT from the memory.

[12_Square]

Did you clear all the LTFT from the memory.

How do I do that? I left the battery unplugged for a while, then flashed with the new tune. Figured that would clean memory out of the computer. What's another way?

[12_Square]

B4206:

in OL, uses STFT's to trim on cells in B3605 that are stoich (Lambda 1.00)... for cells that are not stoich, there is no trimming.

This could be useful. I'll get the hang of all this eventually!

[5.7ute]

How do I do that? I left the battery unplugged for a while, then flashed with the new tune. Figured that would clean memory out of the computer. What's another way?

In the scan tool BIDI controls there is a clear learned fuel trims option.