The STFT is used to keep the AFR stoich in closed loop. LTFTs are developed using the STFT to make corrections across the board. This is to keep up with any fuel system degradation over time. If your fuel injectors started to clog or the fuel pump started to lose pressure, then that would affect AFR. The STFT would compensate for this change in closed loop and the LTFT would compensate while in open loop. Otherwise, a car a few years old would run the risk of leaning out under load as the fuel system performance degraded. If fuel trims exceed 25% correction, then codes are thrown to let you know there is a problem. Now, since the car is relatively new, the fuel system should be good. But, once you start messing with things, your trims are going to try to compensate for the changes. That's why its always important to make sure your fuel trims are in check before you do any tuning.

 

your hope is that both remain low. zero is difficult to attain and the trims are affected every time the ecu adds gas for some reason.

so in logworks you would want numbers, plus or minus, from zero to twenty or so.
now, as I said the trims are affected by a breeze and it takes about ten minutes of driving to get them to react. So the AC could have an impact, a cold morning, anything that adds or subtracts gas temporarily will make the trims read for that special condition.

as I understand it short term is idle trim, med term is cruise. So if one is off you attack it independently if the other is OK.

according to some the short and long term trims are mislabeled in evoscan in the current issue,(new one out anyday).

 

Welcome to overly monitoring your car with logging syndrom.

I have it too, your tuning hobby has become an addiction, you log many times daily and flash several times weekly for perfect tune and learning. Slight changes in boost, fuel, temperature, even the amount and kind of gas in tank will change your AFR. Even PVCCV leaking a little oil at times will do that considerably (oil catch fix).

It likely not a boost leak for that would be the first place to look.

Man, my car does this all the time, just wait until it starts to go leaner before your eyes

 

Very well said...I think I am addicted to tuning and monitoring. During the past month I have flashed my ECU almost daily while testing this, that and the other. I have lamost 100 logs and have flashed the ECU 25-30 times.

On Sunday, I thought I had it all down, but Monday rolled around and I got this new crap to deal with. You are right that it drives you crazy after a while.

 

I did a log this morning and the same thing happened as before.

I also logged STFT amd MTFT and found out that they are off. The STFT was between +26 and +31 and the MTFT was between +42 and +34 during the 35-40 minute trip to work.

If it odd that this would happen since I am running stock injectors and IIRC trims are adjusted to dial in bigger injectors.

How do I fix the trims and get them back to as close to zero as possible?

 

With your level mods you have no reason to be adjusting trims, there must be something else causing this, maybe an air leak of some sort, DV sticking etc.

 

This does sound strange. Be sure that your logging program is accurately capturing trims, first of all. I'd double check these findings using Mitsulogger and EvoScan. If they are, in fact, off by a large margin (over 10% either way), ensure that your scaling is still at the stock 513 setting and that your voltage latency table is 100% stock...particularly in the 11v and 14v fields.

Also, there is no such thing as "MTFT" to my knowledge. There's Long Term Fuel Trim (LTFT) and Short Term Fuel Trim (STFT). There are 3 varieties of LTFT; low, high, and mid. There is only one STFT, and that's your O2 Feedback signal. You may want to read up on how to dial these in. Several threads offer successful methods.

As the last poster said, though, with stock injectors, you shouldn't need to dial them in at all. Either something is incorrect in your ROM (may be the case since you've been tinkering with it), or there may be a mechanical issue on your car (less likely).

I can help you with this at the next Long Beach meet if you'd like. I tuned a car out there last night, but didn't see you.

 

I do not think that it is mechanical because the AFRs are spot on when I flash the car and log immediately thereafter. They are even fine when the car sits for a few hours. It is after more hourse pass or the next day that the AFRs become rich in the 3000-6000 range.

 

Did you change anything other than Mivec, fuel or timing maps? ie. open loop maps, accel enrichment, maf scaling?
I remember that my car felt inconsistant when I changed load values in open loop map 2 but failed to make the changes 4krpm on in open loop 1

 

NJ, did you do a couple of logs in the morning or just one?

 

wait a minute, if you are using logworks it reads in a different scale than mitsulogger.
a 25 in logworks equates to about a 7 or so in MJ's logger.

 

I have changed:

The three high octane ignition maps
The high octane fuel map
Mivec map
BDEL
MWGDC
Rev limit
2 byte load
lean spool tables added
changed values to log JDM MAP

That is all that I have done. I have not touched anything else.

 

I did one in the morning and two in the afternoon on my way back from work. Same result on all three. Rich AFR from 3-6K and then back to the normal lean 6k and after.

 

How long is your commute? And is there big temperature swing between am and pm? Also as you progressed in your tuning was there a point after a change/flash this symptom started? Your best shot is try to reconstruct the sequence of changes and work back.

 

Chart IPW vs 2byte air with a log when it was leaner and from a log that's is rich, but both with same boost. load, gear, and so forth.

If the IPW and air readings are similar then the WB is causing it (cal or something) or there is an intermittent exhaust leak. Note: that exhaust leaks seem to go lean at idle.

If the IPW and air readings are different, then perhaps boost leak, or like you said DV, or even the orientation of the airbox, air duct, MAF.

It's got to be something if 1.0 points richer, but if 0.6 or less difference between AFR on same tune, boost, temp, fuel and humidity occur with me constantly however I also have a separate WM system that bungles the tune at times.