Weird LTFT issue.

[TeacherCreature]

Hi All,

I own an L67 I have CAI, Catless SLP Headers, and recently went up to 3.5 from a 3.4 pulley for the winter.

I am somewhat new to tuning, and I am having a problem getting my LTFT to lock in at 0.
Everytime I make a fuel change and reset my LTFT monitors. After I do a few driving cycles the LTFT starts locking in at 0 or -0.7
A week later that will jump to -1.6 for no reason,
a week later -2.1
a week later -3.1
a week later -3.9
and now -4.6

needless to say my KR is jumping with them. I drive 125 miles a day, and the tempature has been in the 50s the entire time. I did not make any changes during this time period and I noticed this happen two months ago with 3.4 pulley and now happening again with the 3.5 pulley can anyone suggest perhaps maintnance issues that could cause this or other tuning issues.

In general the car runs amazingly and most of the maintenance is good plugs wires oil etc etc

[Perforator]

Have you tuned your MAF yet? If not, when you reset your fuel trims, eventually they will settle back.

[TeacherCreature]

Nah I am new I tried desperately to do the VE tuning nad I felt like the trims never lined up well, so a friend had a zpp 1.0 and I used their ve table. MAF is on my list to learn but the very few tutorials that exist are horribly written.

I thoguht that the form of settling your talking about would take a day or two or a few driving cycles ?
Could it take weeks?

[Perforator]

It depends. LTFT's are a rolling average. If you get a bad batch of gas or the temperatures or humidity change, LTFT's will change accordingly.

[TeacherCreature]

Gas is always from quickcheck same place, tempature as stated was in teh 50 teh whole time, humidity of course did change it went up and down over 5 weks however the ltft didnt go up and down it just went down down down.

Anyone else have any ideas?

[dlagrua]

Hi All,

I own an L67 I have CAI, Catless SLP Headers, and recently went up to 3.5 from a 3.4 pulley for the winter.

I am somewhat new to tuning, and I am having a problem getting my LTFT to lock in at 0.
Everytime I make a fuel change and reset my LTFT monitors. After I do a few driving cycles the LTFT starts locking in at 0 or -0.7
A week later that will jump to -1.6 for no reason,
a week later -2.1
a week later -3.1
a week later -3.9
and now -4.6

needless to say my KR is jumping with them. I drive 125 miles a day, and the tempature has been in the 50s the entire time. I did not make any changes during this time period and I noticed this happen two months ago with 3.4 pulley and now happening again with the 3.5 pulley can anyone suggest perhaps maintnance issues that could cause this or other tuning issues.

In general the car runs amazingly and most of the maintenance is good plugs wires oil etc etc

I would first determine when the KR's are occuring and under what conditions. Do a complete running scan, save the data and analyze it. Sounds like you are running lean at a few points in the RPM curve. If KRs ocur in the PE cycle only, then a tweak to the PE vs RPM vs time tabe is in order. If the KR's happen routinely under many conditions then I would say that the MAF curve needs to be changed.

[WS6FirebirdTA00]

Before you start to worry about things, tune it right first.

[TeacherCreature]

I would first determine when the KR's are occuring and under what conditions. Do a complete running scan, save the data and analyze it. Sounds like you are running lean at a few points in the RPM curve. If KRs ocur in the PE cycle only, then a tweak to the PE vs RPM vs time tabe is in order. If the KR's happen routinely under many conditions then I would say that the MAF curve needs to be changed.

Thank you for the best response so far. I have scanned it and the KR is in PE only. That is the table I have been platying with.

It runs lean at high rpm wot, and that is the primary spot I get KR. Although the weather just dropped 20 degrees and I scanned it again and I got KR through most of 2nd gear at wot PE mode.
Mind you not a lot of KR 1 - 3 * but I want zero, and I dont know if the LTFT are related or not. I feel like I am constantly tuning the car and I was wondering if the LTFT part meant something else was wrong and my tune wont sitck meaning I was wasting my time.

[WS6FirebirdTA00]

Before you start to worry about things, tune it right first.

[Perforator]

You need to tune your MAF to get your long term fuel trims in line.

[yvangkwheng]

u gotta tune it rite

[Beau]

I'm not a MAF tuner but. The Maf is tuned and calibrated for its container.... So it shouldn't ever need to be calibrated again.

The GTP is the one vehicle since it's not intercooled that knocks more when its cold, because your boost will go UP, pulling your further out of the blowers already aweful Adiabatic effiency range (which is only like 40% at its peak anyways).

The cold air doesn't always help for knock UNLESS the vehicle is heat soaked then it'll help some, but nevertheless, I would just start with something small like IAT tuning or even better actually adjust the table. Simply add a splash of fuel as your MAP pressure goes up. I woudln't touch the MAF, nothing has changed with it.

Then again I'm used to tuning Supras with no Maf so.

[WS6FirebirdTA00]

So it shouldn't ever need to be calibrated again.

Completely incorrect. Variance in the intake and from other mods can drastically change a MAF calibration.

[Beau]

That just doesn't make any sense. I'm not saying your wrong of course i'm just saying it's purpose is to send a voltage based on the COOLING effect on a a heater wire which is resistence... It's calibrated for a constant that is the diameter of the pipe. I just don't understand why.

[WS6FirebirdTA00]

And as the air going through the sensor has various streams due to orientation or intake mods, it will change. I calibrated a MAF curve on my car and the same exact sensor on another car was off between 10 and 20%. It all depends how the sensor sees the airflow.

[Beau]

I just can't see it being that useful then, because each MAF ISN'T calibrated for each car from the factory, and if your saying your calibration wouldnt work on somone elses car with the same setup, It just doesn't jive right.

What would be the point, I mean if you wanted to retune for every little event you might as well go MAP.

[WS6FirebirdTA00]

That will change from car to car as well. If you want to half ass it, that is not a problem, don't calibrate it. Most people buy this software because they want to do it correctly. Even from the factory there is a large variance from car to car even with the same intake setup (although most stock setups tend, IMO, to be a little friendlier to the MAF). Why do you think there are fuel trims? There are calibration uncertainties and tolerances on all instrumentation.

The newer stuff, like the LS2 and LS3 cars, have a much closer calibration in stock form.

[TeacherCreature]

Hey Beau I live 20 miles from you so if at anytime you want to meet in person and look at it let me know.
I added some fuel and my LTFT seem constant now at -3.1 but if I am not mistaken doesnt that mean it is pulling fuel because I am rich?

I did see les kr as a result of adding fuel and I am running 18 - 19* timing advance since I went up a pulley for the cold winter.

[Beau]

Hey man, thank you. The tuning would be for my LY7 08 Aura XR.
I've had some decent luck tuning the L67 in the past but I'll have to admit it was using a competitors software/hardware.

I would like to meet up, maybe over some eat at a diner, you could show me the software? I've done some extensive tuning for MAFless AEMs, but GM pcms are much more complicated, save the things you never have to touch like ignition syncing etc. :]

[TeacherCreature]

Yea I am new to it myself, but I am a fast learn. I live in Middletown and work in Kingston and Newburgh.

I also used someone elses to start I used ZZPs tune for my VE tuning, and then kind of built off of it.