How's does long-term and short-term fuel trim work on OBD II vehicles
12-26-2006, 05:30 PM
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How's does long-term and short-term fuel trim work on OBD II vehicles
Anyone have any links or any information about how it actually work and makes changes? Thanks
12-27-2006, 07:18 AM
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Re: How's does long-term and short-term fuel trim work on OBD II vehicles (2CamKilla)
http://www.autoshop101.com/forms/h48.pdf
Look at the third and fourth pages.
I just googled it real quick....there's more.
Basically long term doesn't move much unless there is a major problem.
Short term is using the sensors and doing quick corrections.
Now if short term goes real lean (like a vacuum leak)then long term will step toward rich to balance it and make the correction.
Both trims only have so much they can correct.
Hope this helps and if you have anymore q's just ask!
Look at the third and fourth pages.
I just googled it real quick....there's more.
Basically long term doesn't move much unless there is a major problem.
Short term is using the sensors and doing quick corrections.
Now if short term goes real lean (like a vacuum leak)then long term will step toward rich to balance it and make the correction.
Both trims only have so much they can correct.
Hope this helps and if you have anymore q's just ask!
12-27-2006, 10:52 AM
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Re: How's does long-term and short-term fuel trim work on OBD II vehicles (thesmogman)
that's a lot of info thanks a lot! 
i will thanks.
i will thanks.
12-27-2006, 12:12 PM
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Re: How's does long-term and short-term fuel trim work on OBD II vehicles (2CamKilla)
another trick it to feed the oxygen sensor a fixed signal with something like a 555 timing chip to swing a fixed signal....then you can manipulate a/f through map/maf signal manipulation without the ecu trying to correct for you...incase your trying to tune a obd2 car
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