Fuel Trims Question

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Jul 6, 2009 | 01:23 AM

RevGTO

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Fuel Trims Question

Do long term fuel trims function on the basis of O2 sensor feedback alone, or do other calculations figure into the equation? Example: Commanded AFR/IAT/ECT result in fuel trimming?

I'm working on my OLMAF tune and wondering if I should have disabled LTFTs.

Thanks for any help ...

Jul 6, 2009 | 05:53 AM

macca_779

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From: Katherine N.T Australia

Hell yes you should disable LTFT's.
LTFT's are built off STFT averages and then stored for permanent reference. If you don't zero them prior to trying to dial in a MAF or VE. The stored values are still effecting primary fuelling.

Jul 6, 2009 | 08:14 AM

ringram

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Best to disable LTFT IMO anyway,
They are evil and will come back to rape you sooner or later.

Jul 6, 2009 | 09:28 PM

RevGTO

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Well, yes, I disabled them when I went full time open loop and ditched my O2 sensors. Just wondering if they were supposed to function even without the O2 sensors.

Thanks guys.

Dec 18, 2010 | 01:22 PM

Pavetim

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so you can leave your LTFT disabled and it won't hurt anything? Will it still correct for altitude and baro changes with LTFT disabled?

Dec 18, 2010 | 02:39 PM

macca_779

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From: Katherine N.T Australia

Quote:

Originally Posted by Pavetim

so you can leave your LTFT disabled and it won't hurt anything? Will it still correct for altitude and baro changes with LTFT disabled?

Yes. LTFT's are only there to correct for errors. If there are none then they are useless.

Dec 18, 2010 | 03:04 PM

Pavetim

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But what do you mean by errors? Errors in the tune or errors in say if you drive from florida to colorado?

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Dec 18, 2010 | 06:06 PM

macca_779

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From: Katherine N.T Australia

Quote:

Originally Posted by Pavetim

But what do you mean by errors? Errors in the tune or errors in say if you drive from florida to colorado?

Tune mate

Dec 18, 2010 | 06:51 PM

#10

disc0monkey

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Quote:

Originally Posted by macca_779

Tune mate

huh ?

Dec 19, 2010 | 12:35 AM

#11

tording99Z28

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Errors in your tune. If your tune is spot on and your STFT's are very close to 0 then the LTFT's do nothing and therefore could be left off is what they are saying.