Fuel Trims & The Tuning Process

Frustrated by fuel trims? We’ve got you covered! Our instructor Gerrot Jacobson explains what they are and what to look for in your diagnosis.
00:30 Base fuel tables
1:08 Scanner fuel trims
1:30 Short-term fuel trims
1:49 Long-term fuel trims
3:01 Fuel trim chart
3:52 Diagnostics
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[@foxsetup]

Nice bits of knowledge for the beginners ! wish i had those when i started tuning

[@TheTuningSchool]

You're appreciated!

[@eddieweaver3609]

Subscribed. I very much enjoy the videos. I am learning to tune and knowledge is the key. Thank you very much.

[@nukeguyge]

I appreciate these little nuggets of knowledge! Keep up the good work!

[@TheTuningSchool]

Thank you for watching!

[@kolemieux]

Very well done! Thanks

[@TheTuningSchool]

Thanks for watching!

[@trealwilliams1563]

Man.... This is such a clear explanation 👨‍🔧🛠️🛠️🛠️🛠️🛠️ Five Star Wrenches 👍

[@upptowne]

thank you

[@Fractal_CZ]

Thank you so much!

[@TheTuningSchool]

No doubt! Thank you for watching

[@Fayis1341]

Good one ❤

[@Artoconnell]

Thank you very much

[@AlexErnst83716]

Can-o-worms warning: In MAF systems specifically, consider MAF table characterization before changing VE tables (or other variables impacting VVE table where applicable). An improperly characterized MAF table will affect PE/WOT/CL too- not just drive a wonky fuel trims table, depending on the system type and how much it relies on MAF data during PE. There is an awful lot more to this subject, just be aware it is a thing, if you are having trouble with fuel trims enough to throw codes, particularly if the error/correction is a linearly-increasing error. (And clean your sensor by-the-book first before doing anything!)

[@ankurpatil8628]

Thank for basic info. Could you help me make sense of these STFT and LTFT values. I have 07 ford taurus, for bank 1 STFT stays between +/-3%, but LTFT stays constant at about -12% at Idle. Bank 2 is lean at idle with +12% total fuel trim. When I increase RPM to 2500, STFT jumps between +/-6% and LTFT stays constant at -19%. Bank 2 improves at 2500 RPM with about +6% total fuel trim. OBD says cylinder 1,2, and 6 misfire. I have tested injectors, replaced the leaking injector already. What do these trim value mean? How come bank 1 is rich and bank 2 is lean? Thank you.

[@fasnuf]

good info

[@TheTuningSchool]

Thanks for watching!

[@ForzaRT]

Can I run without long fuel trim? How does it affect? What is the period of time that long fuel trims needs for display the value? Thanks.

[@franchise-pj6ow]

Is the chart the same for 3rd gen hemi's ? I've researched something that appeared dodge was backwards meaning negative is adding fuel and positive numbers is removing fuel. What is the truth on that ? Thanks in advance !

[@trevorseals6588]

What is the time it takes for short term fuel trim to become long term? And more importantly, does long term get deleted when you flash a new tune or disconnect the battery?

[@williamb2013]

Does STFT adjust when decelerating to a stop? Mine is dropping rpm and sometimes dies when coming to a stop.

[@mark98070]

I have an older Ford truck with the EEC IV system. STFT is normal but LTFT is -56! I have replaced the ECM but Long term is still reading -56. Have disconnected battery thinking the KAM would have been cleared. Shouldn't this have been cleared? At times the engine runs a bit lumpy, but runs okay otherwise

[@trealwilliams1563]

How to get started with the software??? Budget buy, substitutes, ect???

[@labalade77]

Could you explain the VVE in hp tuners. I tried to adjust vve after logged in data from ltft but I don't understand this process. Thank you and all the best

[@TheTuningSchool]

It all depends. If you still need assistance, contact us and we can give you more details than we can type!

[@jakelogan7542]

Another possibility for a lean condition is a leaky manifold gasket. Unmetered air will enter and the 02 sensor will in turn see a lean condition for that bank.

[@arthurrondey6874]

Good video. Easy talking points. So to clarify what you are saying for data logging, is it best to gather data over a week or month and then looking at the data? Or maybe a specific amount of miles? And to clarify, if the fuel trim cell shows 0, it is perfect. But if it shows -10, does that mean I need to ADD that trim value in fuel to the overall value? Like, numeric value of 1042 + 10, to make the new fuel value 1052? Or is my math incorrect? - means ADD FUEL? + means SUBTRACT FUEL? Like, a cell has 34 (Blue) means it is rich. So I need to subtract 34 from the cell numeric value of 191, for a new fuel value of 157? Perhaps you can clarify my cells: Blue Cell +41 / Red Cell -178. How would I make my adjustments?

[@Charkatak]

Hey! Very interesting video! My car shows about 1.5 to 2% LTFT and about 3 to 4% of STFT(can be higher at times) and MAF is about 4g/s and Closed loop. Are the readings normal at idle?

[@chickenfixn4439]

I'm learning tunes rn but I have mechanic experience. I know its been a year but maybe youd still like to know, you want your g/s to be no less than your displacement in the motor. In my case its 2.5 g/s and higher

[@Charkatak]

@@chickenfixn4439 Thanks for your reply. Yeah, it has been a year. I haven't played with trims since that time, but engine size is 3.7L. MAF g/s showed about 3.8g/s and up to 4 g/s when idle. I guess it is normal then. When I asked the question, I wanted to find out why fuel trims were a bit lean and if I could make my car get better gas mileage. If fuel trims in my first message don't look high then I am happy.

[@dhiquobgnaloo]

Hi Gerrot when i looked into my tune my tuner on my supercharged l98 had turned off the long term trims and was only running on the short term trims is this a problem or is it common.

[@TheTuningSchool]

It is common amongst tuners but in our experience the vehicle will run much better at part throttle with the long term fuel trims turned on. The process we teach here at The Tuning School does not have you turn off the LTFT’s and our GM Instructors usually advise against the practice. All that being said, it is not a dire problem.

[@trealwilliams1563]

What's the cheapest & best software and hardware to adjust A/F mixture to get it nearly perfect or on the money? I liked the video but please tell us and how with what afore said!

[@TheTuningSchool]

Check us out >> thetuningschool.com/collections/new-to-tuning Feel free to give us a call to give us more information about your vehicle, and we can help you from there!

[@AtanasDimitrov954RR]

great video. why cant we just have short trim always? im still trying understand need for long trim. yes its over a period of time, not instant changes. but again, why do we need this?

[@TheTuningSchool]

Thanks for watching! Join us at one of our classes and we can give you more details (or just give us a call)

[@moccasinmarine]

Long term FT is saved after the key is cut off. Short trim is not. That way pcm doesn’t have to relearn what it already has the previous drive.

[@Onalky87]

My stft says it’s pulling a lot of fuel at idle and cruising after I tuned my wideband to 14.7. Why would that happen? If I remove fuel wouldn’t my wideband say even leaner? Or will it stay 14.7 but stft will pull less fuel?

[@Poppacapp1234]

Stoich will be 14.1 with regular fuel and the standard 10% ethanol added.

[@Onalky87]

Poppacapp1234 I’m on racegas

[@fasnuf]

@@Onalky87 The WB is calibrated for 14.7 and the stoich ratio of your racegas is what?

[@jamesbtri]

What is your working with a ANN system? The short terms dont seem to have judgment on anything ?

[@TheTuningSchool]

Check out this video on ANN's kzbin.info/www/bejne/kInMhqegbcmpkMU and a little more from Bob on ANN's at this seminar thetuningschool.com/blogs/news/2019-pri-education-seminar

[@4BillC]

My computer has 5 VE tables and the numbers inside read like 2035.8846 instead of 77...

[@adamweaver6351]

Whys my car have negative fuel trims and its lean on the wide band

[@613Builds]

i think im having the same issue. my LTFT says -15% but its actually running too lean

[@adamweaver6351]

@@613Builds Honestly im pretty sure i had a bad wide band. i think it was showing 19 most of the time because it wasnt reading properly. My motor has been running with the same set up for years and never burnt a piston so it makes no sense for it to be running lean. Make sure your wide band is good, then let me know what you find out.

[@ChannelZeroOne]

How would a cat delete affect this?

[@TheTuningSchool]

It would not affect the fuel trim reading on a GM vehicle in any way.

[@ChannelZeroOne]

@@TheTuningSchool How about an 04 liberty?

[@rebdawi2002]

My car is having Short fuel Trim "-30" and error code: P0301! I changed spark plugs, ignition coils and fuel injectors but care doesn't go over 20 mph and check engine is blinking. it's driving me crazy.

[@suspectedwill1]

I own hp tuners and it sucks its old technology im about to sell my pos mp2 for 100 bucks and go buy a real system HOLLEY

[@jimbrown563]

I wish I could find something good to say, really, but this was a waste of time. Aside from incoherent sentence structure, anyone who is currently working on an engine computer, knew all this at least 5 years ago. And if they didn't, they might just wind-up destroying a perfectly good engine.

[@4BillC]

It's not even like he told you what to do the information. Just what a fuel trim is...

[@brettus9115]

@@4BillC Pretty much! They all seem to dance around the actual tuning side of it. Secret Squirrel.....

[@4BillC]

@@brettus9115 commercials... That's all it really is.

[@Poppacapp1234]

@@brettus9115 They sell courses on the tuning. I have their advanced GM GenV books. They are very good

[@TheTuningSchool]

Thanks for your insight! We know that there are all levels of tuners out there, but this one was specifically for our newcomers who wanted a bite sized version of the massive amounts of knowledge there is out there. Plus, we try to save the good stuff for class!