When is it necessary to reset fuel trims?
When is it necessary to reset fuel trims? On hptuners theres a button to reset fuel trims.
When would you ever reset them?
After a new exhaust, etc?
What if you put your new parts on and never reset them, wouldn't they evetually learn?
When would you ever reset them?
After a new exhaust, etc?
What if you put your new parts on and never reset them, wouldn't they evetually learn?
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Well, you would want to reset fuel trims any time you made a modification that alters your engines ability to breathe, or any time you make a tuning change that alters your air fuel ratio.
For example, just putting a lid on a LS1 can significantly alter your fuel trims (most people go +Ltrims with lid). Tuning wise, when mapping your VE Table, MAF calibration, etc., you would reset your fuel trims. Otherwise the change you make will still have Trims learned from a previous runs and you will not be able to successfully determine how your new change has altered your fueling.
In general, running +Ltrims will alter your WOT fueling. The PCM will add that percentage of +Ltrim to the WOT fueling. I.E., you will be richer. You will never be able to hit your WOT AFR that way.
Hope that helps. There is a lot of the same information in the Stickies. You may find that helpful.
Good luck.
..WeathermanShawn..
For example, just putting a lid on a LS1 can significantly alter your fuel trims (most people go +Ltrims with lid). Tuning wise, when mapping your VE Table, MAF calibration, etc., you would reset your fuel trims. Otherwise the change you make will still have Trims learned from a previous runs and you will not be able to successfully determine how your new change has altered your fueling.
In general, running +Ltrims will alter your WOT fueling. The PCM will add that percentage of +Ltrim to the WOT fueling. I.E., you will be richer. You will never be able to hit your WOT AFR that way.
Hope that helps. There is a lot of the same information in the Stickies. You may find that helpful.
Good luck.
..WeathermanShawn..
I am having problems with positive fuel trims.
When I got the car it had just a lid and Racetronics pump/harness.
(it was put back to stock before I got it, except for those parts)
When I got it running the trims never came out of the negative.
I even scaled the IFR table because it was reading 65 psi fuel pressure, I scaled each cell with the hp tuners calculator based off fuel pressure change from 58 to 65. And it still ran maybe -8 at the average lowest, but WOT always went to 0
Then I put headers and an ORY on it.
I know I logged it and the trims were the same pretty much.
Then I put a hooker aerochamber on it with a 3" pipe to the ORY.
Then even further on I put in a 3600 converter, and tuned codes for that.
When logging the converter runs I noticed positive trims. And worse off +3 to +5 at WOT. And it's reading low 10:1 AFR at WOT
I runs good for just a lid and exhaust, ran low 12's, I know the wideband is good also.
Thats where I'm at now.
I have read stickys here, Google, etc. Since every engine is different I don't know what direction to go.
Anyway, I guess I should hit reset fuel trims after each change? I'll do that.
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One technique is to log MAF frequency against Trim values. With enough data and proper filters and if your VE Table is accurate, you can usually just apply the Freq vs Ltrim %, cut and paste the difference back into the tune..reset trims and try it again.
With a 10:1 AFR, at WOT, have you disabled your Catalytic Converter Protection? With it enabled you will really be rich.
As indicated a lot of differring tuning techniques. It is true some people do not even utilize LTrims. I prefer them. LTrims average out any large swing in STrims that can arise on any given day. In any case, with or without LTrims enabled you want to have your fueling accurate.
And of course the mandatory disclaimer..Always utilize a wideband and have an accurate VE Table.
Good luck. Sounds like you are on the right track.
..WeathermanShawn..
With a 10:1 AFR, at WOT, have you disabled your Catalytic Converter Protection? With it enabled you will really be rich.
As indicated a lot of differring tuning techniques. It is true some people do not even utilize LTrims. I prefer them. LTrims average out any large swing in STrims that can arise on any given day. In any case, with or without LTrims enabled you want to have your fueling accurate.
And of course the mandatory disclaimer..Always utilize a wideband and have an accurate VE Table.
Good luck. Sounds like you are on the right track.
..WeathermanShawn..
Yes, my COT is disabled.
I might slowly be making progress.
But I want to ask, and in simplest of terms. The engine is a big air pump (as we've all heard), when you make it move more air you need to add more fuel right. So the positive fuel trims I'm seeing is the ECM adding more fuel? And what I need to do now change the programming a bit to where it gets that extra fuel without relying so much on the fuel trims to add it?
I might slowly be making progress.
But I want to ask, and in simplest of terms. The engine is a big air pump (as we've all heard), when you make it move more air you need to add more fuel right. So the positive fuel trims I'm seeing is the ECM adding more fuel? And what I need to do now change the programming a bit to where it gets that extra fuel without relying so much on the fuel trims to add it?
TECH Enthusiast
iTrader: (1)
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From: Denver International Airport, Colorado USA
Yes, my COT is disabled.
I might slowly be making progress.
But I want to ask, and in simplest of terms. The engine is a big air pump (as we've all heard), when you make it move more air you need to add more fuel right. So the positive fuel trims I'm seeing is the ECM adding more fuel? And what I need to do now change the programming a bit to where it gets that extra fuel without relying so much on the fuel trims to add it?
I might slowly be making progress.
But I want to ask, and in simplest of terms. The engine is a big air pump (as we've all heard), when you make it move more air you need to add more fuel right. So the positive fuel trims I'm seeing is the ECM adding more fuel? And what I need to do now change the programming a bit to where it gets that extra fuel without relying so much on the fuel trims to add it?
You said it perfectly.
..WeathermanShawn..
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Verdad Gallardo Ok, I changed my tune and reset fuel trims. Had to go on a highway run anyway so I logged it. First run I only logged 16 minutes, got fuel and continued logging 33 more minutes.
On the way back I pulled off onto a country road and did a hard 3/4 mile run. (at the end of the scan)
It looks good as far as fuel trims and what I know.
I seen the LTFT's run average around +2, -4, and if it was in the positive it would go right to zero with increased throttle.
Now the bad part is my wideband took a crap, so it looks good.
I have a new one coming next week that will be permanently installed.
The question: How long does it take to relearn? I guess when it's hit all the cells under various conditions?
In other words, when can I consider my LTFT's settled?
I'll attach the scans, I don't expect anyone to view them unless they're really bored or curious.
first april scan.hpl = 16 minutes mostly highway.
april 02 hiway run.hpl = 33 minutes all highway, some variation, some with cruise control.
april02WOTRUNS.hpl = highway, short WOT at 5:40, 15:53, and hard 3/4 mile WOT at 24:00 - easing into it.
On the way back I pulled off onto a country road and did a hard 3/4 mile run. (at the end of the scan)
It looks good as far as fuel trims and what I know.
I seen the LTFT's run average around +2, -4, and if it was in the positive it would go right to zero with increased throttle.
Now the bad part is my wideband took a crap, so it looks good.
I have a new one coming next week that will be permanently installed.
The question: How long does it take to relearn? I guess when it's hit all the cells under various conditions?
In other words, when can I consider my LTFT's settled?
I'll attach the scans, I don't expect anyone to view them unless they're really bored or curious.
first april scan.hpl = 16 minutes mostly highway.
april 02 hiway run.hpl = 33 minutes all highway, some variation, some with cruise control.
april02WOTRUNS.hpl = highway, short WOT at 5:40, 15:53, and hard 3/4 mile WOT at 24:00 - easing into it.
Last edited by 2002CAMAROSSLS1T56; May 12, 2009 at 12:25 AM.
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I am sure someone knows the exact answer, but I usually consider them 'settled' after I run a through full tank of gas.
Not to over complicate the answer, but in my case I reconfigured the Trim RPM/MAP boundaries from the stock 02 Camaro to the 02 Z06. Whether that change lengthens the learning time, I do not know for sure.
I say a full tank of gas because if you have too much time on your hands, you can log fuel trims after a gasoline fill-up and watch them go -10 to -15 negative for about 10-15 miles. If you are trying to do an average, I consider it a bias.
Once you hit 200-300 miles over a few days, job done.
..WeathermanShawn..
Not to over complicate the answer, but in my case I reconfigured the Trim RPM/MAP boundaries from the stock 02 Camaro to the 02 Z06. Whether that change lengthens the learning time, I do not know for sure.
I say a full tank of gas because if you have too much time on your hands, you can log fuel trims after a gasoline fill-up and watch them go -10 to -15 negative for about 10-15 miles. If you are trying to do an average, I consider it a bias.
Once you hit 200-300 miles over a few days, job done.
..WeathermanShawn..
