What determines stft during open loop?

5.0 Hatch

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I ask because my stft is off bank to bank (bank 1 is around 1.05, bank 2 is around -.80) during open loop. Once the car hits 180 degrees, everything is balanced bank to bank.

I cleared the KAM and nothing changed. 2001 cobra.
 

01yellercobra

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It should be the MAF curve and some kind of warm up table. I wouldn't worry about it too much if the car is running ok. Is the car tuned?
 

5.0 Hatch

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What are the o2's reading during warm up? Sounds like b2 is stuck reading rich.
I don't think open loop reads the o2's
It should be the MAF curve and some kind of warm up table. I wouldn't worry about it too much if the car is running ok. Is the car tuned?
Runs ok but smokes a bit before going in to closed loop. Yes tuned. It's actually better after the tune but still not perfect.
 

2003RedfireVert

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I ran my car in open loop for several weeks and monitored AFR on my wideband to tweak the whole curve. My curve needed a lot of fuel added down low and some fuel removed up top. My tuner got it “close” but it needed work. Once it got it close turned on close loop and it’s now within 5% on the trims at idle and cruising. Obviously could be closer but I’m happy with it. Good luck.
 

2003RedfireVert

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Okay. Maybe I'm overthinking it but it seems like any change there would affect both banks?
Yes it would effect both banks. I don’t know your mods or setup but a cheap test would be swap O2 between banks.

If it fixes itself in closed loop with no codes, that tells me it’s a MAF curve problem.
 

smashedheadcat

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It’s been a million years since I’ve messed with this stuff, but did you (or can you) log “fuel source” when you’re seeing this

I can’t see how or why you’d ever see the ecu command such a spread between banks, so I’m thinking you might actually be in closed loop for one reason or another.
 

01yellercobra

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But if it's fine when it warms up I don't know that the MAF curve needs work. Unless the long term fuel trims are way off the chart to bring everything in.

Granted I don't remember messing with the warm up stuff too much on the stock ECU. Aside from lowering the warm up temp.

If the LTFT are within spec, or even turned off, I'd look into the warm up side of things. Since the ECU isn't actually correcting in open loop and just going off what is in the tune.
 

2003RedfireVert

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But if it's fine when it warms up I don't know that the MAF curve needs work. Unless the long term fuel trims are way off the chart to bring everything in.

Granted I don't remember messing with the warm up stuff too much on the stock ECU. Aside from lowering the warm up temp.

If the LTFT are within spec, or even turned off, I'd look into the warm up side of things. Since the ECU isn't actually correcting in open loop and just going off what is in the tune.
Good point.
 

5.0 Hatch

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Thanks guys. I'll log the fuel source on warmup and see if it sheds any light. The car has o/r exhaust and otherwise stock.
 

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