Clarification please on O2 sensors and STFT.

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delcowizzid
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Re: Clarification please on O2 sensors and STFT.

Post by delcowizzid »

The swinging also fills the catalytic convertor with excess o2 each swing lean so it can do its job burning off the bad stuff
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem
JohnDee68
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Re: Clarification please on O2 sensors and STFT.

Post by JohnDee68 »

Ok, thank you, but if the STFT is showing negatives, is that reducing (leaning) fuel amounts put in to the engine or increasing fuel (richer) ?
i just want to get this stuff clear in my head so i can remember it. :)
ironduke
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Re: Clarification please on O2 sensors and STFT.

Post by ironduke »

JohnDee68 wrote:Ok, thank you, but if the STFT is showing negatives, is that reducing (leaning) fuel amounts put in to the engine or increasing fuel (richer) ?
i just want to get this stuff clear in my head so i can remember it. :)
negative numbers means it's pulling fuel out.. It's leaning it out from what it's calculated for fuel delivery.. You'll always see them doing something..
As far as a stock vehicle If the long term are + or - 10 then I leave it alone. They don't set codes til they get on the high side of 25 plus or minus.
JohnDee68
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Re: Clarification please on O2 sensors and STFT.

Post by JohnDee68 »

just to clarify, as terminology in different industries can reflect different outcomes. When you say "pulling fuel out", do you mean reducing fuel into the combustion chamber or "pulling fuel out" of the injector resulting in more fuel in the combustion chamber?
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delcowizzid
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Re: Clarification please on O2 sensors and STFT.

Post by delcowizzid »

Reducing the amount of fuel injected
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem
JohnDee68
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Re: Clarification please on O2 sensors and STFT.

Post by JohnDee68 »

:thumbup: Ok, thanks guys for your help.
I now understand more and have come to the conclusion as follows.
O2 sensor reading Lower than 500mv = LEAN Condition
O2 sensor reading Higher than 500mv = RICH Condition
STFT & LTFT POSITIVE = ADDING FUEL
STFT & LTFT NEGATIVE = REDUCING FUEL
:thumbup: :thumbup:
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delcowizzid
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Re: Clarification please on O2 sensors and STFT.

Post by delcowizzid »

Only when cruising is that correct. full throttle will be in the mid 0.800 to 0.900 range
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem
JohnDee68
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Re: Clarification please on O2 sensors and STFT.

Post by JohnDee68 »

delcowizzid wrote:Only when cruising is that correct. full throttle will be in the mid 0.800 to 0.900 range
Ok, I will note that. But for me I don't go WOT. I am more a cruise driver. :)
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hsv08
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Re: Clarification please on O2 sensors and STFT.

Post by hsv08 »

I always work off LL = "Low is Lean" Meaning Lower then 500 millivolts.

Depending on how the LT's and ST's are setup in the tune will define there behaviors, ( im sure some of the XDFs allow you to define how many percent your ST's can be before changing the LT's)

But this is why you would normally use the math LTFT + STFT, Your STFT will always move about within a couple percent when fueling is close.


I try to insure that my trims are within a couple percent but always try to stay on the -2-3% mark. Its always better to be a bit richer then leaner.

trims minus = Removing fuel from base VE or MAF based on O2 swings
trims positive = Adding fuel from base VE or MAF based on O2 swings
JohnDee68
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Re: Clarification please on O2 sensors and STFT.

Post by JohnDee68 »

Thanks hsv08,
I like the "LL" method to recall it.
I think I struggle at the moment trying to learn tuning my car. So I'm taking one step at a time.
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