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Fuel trims


06 v-maxx

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where did you hear this... do a proper tune of the VE table and MAF and not worry about it... or make sure you are on a good SD tune and turn everything off altogether.. no need to do things half way. Both LTFT and STFT are good diagnostic tools to have

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whats your take on turning off LTFT and just let the STFT do the work?

 

 

My take is that you need to turn them off to use your wide band to get your VE and MAF correct. After you can turn them on, but they should have little work to do because you have corrected your airflow/fuel to not need (as much) adjusting

 

Now if you are asking about running with them off in a Speed Density (SD) tune there might be more discussion...

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I guess what I was asking was does anyone that has there own tuning software ever turn off there LTFT and just let the STFT make the corrections. this of course after getting TRIMS close to zero as possible, but we all now you can never get them to stay zero. So that being said if you have a zero LTFT on day and the next it is a +2 and you go into pe now you will carry that +2 into pe . But if you have -2 LTFT we know they don't carry over. So for those of you that tune would you rather have slightly negative trims or turn off LTFT. Again this is not for people with mail order tunes who don't have access to there tunes.

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All the guys who have responded here do their own tuning. LTFT at +/- 2 is more than ideal. You will never get perfect fuel trims. No need to adjust them each day. +/- 2 will also not have any impact on how your truck drives or fuels it self nor will it cause engine damage. If you are worried about going lean, which isn't an issue here, you can alway compensate by adding more fuel with PE

 

Sent from my ADR6400L using Tapatalk 2

 

 

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  • 4 weeks later...

For a daily driven street tune I'd recommend keeping the LTFT's on. For a setup that is more of a race vehicle than street vehicle and has a very, very well dialed in tune I turn them off and simply leave the STFT's on. The main reason the LTFT's are desired on the street is that differences in fuel can be compensated for easier as well as a mechanical problem. If you have a vacuum line fall off and only use the STFT's you will be horribly lean if you go wide open where as the LTFT's can help compensate until you fix it. If you are confident of your mechanical side and the tune is very well done you can turn off the LTFT's. You will know right away how good your tune is if you shut off the LTFT's and keep an eye on your STFT's. if you write yourself a track only tune you'll likely want it to be open loop only or open loop with STFT's on.

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