Why the ecu make my tune run richer over time ?

[s2d4]

Originally Posted by coyote

The people having an argument here and talking about two completely different sensors and tables.

Just realised that one person went on the wrong tangent, thanks.

[ft_sjo]

You're not wrong. My first statement about resolution was perfectly valid. I'm not sure why I started talking about the MAF sensor. I won't try and blame it on anything, though.

[s2d4]

Originally Posted by ft_sjo

My first statement about resolution was perfectly valid.

How did you arrive at this conclusion?
You were referencing the wrong sensor?
I am beginning to think you are just as special as regal...

[ft_sjo]

Originally Posted by s2d4

How did you arrive at this conclusion?
You were referencing the wrong sensor?
I am beginning to think you are just as special as regal...

No, the incorrect reference came after that statement, which I identified in my previous post.

I'm not really sure where you guys are taking this thread.

[mad_sb]

Originally Posted by NoFear99

My advance multiplier was playing around .88 and .90 today when i was loging so it was pretty close to 1.

The first picture is the AFR wanted that I got after my last etune reflash on june 26th.

Second and third picture is my afr on july 23th.

I did change the overpipe on july 22th but my afr was already showing 12.17 just before the install. So the overpipe is not the reason why my afr changed that much alone by itself.

If I do a reflash with my last etune I got in june, I bet 100$ my afr will come back to normal where it should be.

Originally Posted by FA20Club.com

why dont you send me the log since you just installed the over pipe and i was expecting your log anyway

Originally Posted by NoFear99

This thread you are refering me seem very interesting but too complicated for me especially when English is not your language.

May be somebody could explain here what this thread is all about in a simple short summary...

Tick the little box in the log viewer that says Long Term Fuel Trim and you will be able to see what i am talking about.

(This is over simplified but should help)
Fuel trims add or remove fuel based on how far off from the target AFR you are. In stock form the ECU only keeps track of target afr when in closed loop mode (targeting roughly 14.7:1 or stoich). Subaru extends the amount of time the ECU is in closed loop mode to comply with various countries emissions regulations. With this strategy (based on timers etc) it is very difficult to predict where on the fuel map a car will be open loop vs closed loop and in fact it could be either open or closed in the same cell depending on when you put your foot down and for how long.

The result of that logic is that, depending on how you drive on a given day and how the fuel map is tuned, you could stack up long term fuel trims. Short term trims are only used in closed loop and when they are consistently positive or negative for a set amount of time they get moved to the long term trim. Long term trims are used all the time (closed and open loop).

So on tuesday you go WOT at 2,000 rpm from a red light and rev it out to 7,400 rpm and have a nice flat 12.8:1 AFR the whole way (assuming you are NA ) and the car feels like a beast. On Wednesday you get stuck behind slow Sally and gear down waiting for your gap in traffic. With the motor on boil at 4,000 rpm you finally see the gap, put the pedal to the floor, and get an overly rich 12.1:1 and a sad panda face as you slowly pass the prius because you stacked up a long term trim while you were waiting for your gap.

Different tuners deal with this problem different ways. Some choose to ignore the issue and claim openly on this form they do not have the problem, even though i have seen it first hand in logs from their tunes over and over again. Some choose to adjust tunes after the long term trims have had time to settle in based on your driving. Others change the way the transition takes place by modifying or removing the timers or the other table limits. And still there are more way to deal with it like turning off long term trims and or rescaling your maf sensor etc etc. I think most combine letting the trims settle and adjusting the timers.

Get some current logs over to Toni and I'm sure he will take care of you. He IS NOT one of the people the pretends the issue does not exist.

[Sportsguy83]

@King Tut

[NoFear99]

Originally Posted by mad_sb

Tick the little box in the log viewer that says Long Term Fuel Trim and you will be able to see what i am talking about.

(This is over simplified but should help)
Fuel trims add or remove fuel based on how far off from the target AFR you are. In stock form the ECU only keeps track of target afr when in closed loop mode (targeting roughly 14.7:1 or stoich). Subaru extends the amount of time the ECU is in closed loop mode to comply with various countries emissions regulations. With this strategy (based on timers etc) it is very difficult to predict where on the fuel map a car will be open loop vs closed loop and in fact it could be either open or closed in the same cell depending on when you put your foot down and for how long.

The result of that logic is that, depending on how you drive on a given day and how the fuel map is tuned, you could stack up long term fuel trims. Short term trims are only used in closed loop and when they are consistently positive or negative for a set amount of time they get moved to the long term trim. Long term trims are used all the time (closed and open loop).

So on tuesday you go WOT at 2,000 rpm from a red light and rev it out to 7,400 rpm and have a nice flat 12.8:1 AFR the whole way (assuming you are NA ) and the car feels like a beast. On Wednesday you get stuck behind slow Sally and gear down waiting for your gap in traffic. With the motor on boil at 4,000 rpm you finally see the gap, put the pedal to the floor, and get an overly rich 12.1:1 and a sad panda face as you slowly pass the prius because you stacked up a long term trim while you were waiting for your gap.

Different tuners deal with this problem different ways. Some choose to ignore the issue and claim openly on this form they do not have the problem, even though i have seen it first hand in logs from their tunes over and over again. Some choose to adjust tunes after the long term trims have had time to settle in based on your driving. Others change the way the transition takes place by modifying or removing the timers or the other table limits. And still there are more way to deal with it like turning off long term trims and or rescaling your maf sensor etc etc. I think most combine letting the trims settle and adjusting the timers.

Get some current logs over to Toni and I'm sure he will take care of you. He IS NOT one of the people the pretends the issue does not exist.

First picture is a log I did july 23th with my ecu flashed june 26th.

Second picture is a log I did july 24th after a fresh reflash the same day.

You was right mad sb, the biggest difference between those 2 logs is the long fuel trim graph. They are totally different and it explain why my afr is so different. My advance multiplier is not the answer to this afr change.

On july 23th, my long fuel trim is between 8.5 to 11%.

On july 24th, my long fuel trim is between 0% and 2%.

So would it be better to disable the long fuel trim if possible ?

[feldy]

Instead of reflashing is it not just possible to reset the ecu via the battery?

[NoFear99]

Originally Posted by feldy

Instead of reflashing is it not just possible to reset the ecu via the battery?

Not sure if the ecu will be completely reset to zero everywhere that way ...

The long term fuel trim memory may not be erased...

[mad_sb]

Originally Posted by NoFear99

...
You was right mad sb...

I know lol

Originally Posted by NoFear99

...
So would it be better to disable the long fuel trim if possible ?

The way I would handle it:
1. Turn off the long term trims by zeroing out the Closed loop AFR A&B tables
2. Set all the Transition timers to zero
3. Set the Min Openloop AFR to 14.5
4. Adjust the Fuel map so AFR target is richer than 14.5 anywhere you want to be openloop
5. Log LOTS of miles with varied driving conditions, wot, cruise, roll-ins at various rpms etc etc
6. Poor over the log data to decide if you need to rescale the maf, tweak some of the comp tables, tweak injector scaling, etc etc

Generally, Once the long term trims are turned off and the timers are zeroed out, it only takes a couple of tweaks to get the short term trims down to +/- 10%. At that point you can experiment with turning the long term trims back on. I always prefer to leave the timers at zero so the transition from closed to open loop is based on engine load, rpm, and desired AFR.

You should start by keeping an eye on things for a couple days while you are logging and see how the long term trims move around. Then you will need to talk with Toni to decide how to handle it. If the long term trims were staying around + / - 5% i would not worry much and just adjust the tune... but +/- 10% is a little much to tune around.

Also, i should mention there are multiple long term trims. The ECU uses bins based on the maf g/s reading. There are 4 bins i believe, idle, low medium and high load. I don't know the exact g/s ranges (that table has not been defined yet). That is why if you go WOT from low rpm, you will see the long term trim change. This also allows you to be clever about the transition points... you can set your fuel map up so that it transitions to openloop at say .8 load at lower rpm and possibly avoid setting the high trim but still keep the afr where you want it... open loop does not have to mean rich afr.

[mad_sb]

Originally Posted by NoFear99

Not sure if the ecu will be completely reset to zero everywhere that way ...

The long term fuel trim memory may not be erased...

^ this.

It's just easier to reflash most of the time. You don't loose your head unit setting etc that way and I'm not positive pulling the battery resets the learned data. I might but that requires a wrench and lifting the hood. I can reflash from my drivers seat

[feldy]

Here is a picture of 3rd gear wot numbers from a fresh flash to the same one 21 days later. not sure what all the numbers mean I know I'm still having some knock and the afr has readjusted itself.

[FA20Club.com]

yeah but you change fuels too and that takes time to adjust since youre using map switching the trims dont reset like if you flashed in a new file when you change fuel. that has to be considered as well. thats why i told you to run through more than a tank after switching before logging.

[feldy]

Originally Posted by FA20Club.com

yeah but you change fuels too and that takes time to adjust since youre using map switching the trims dont reset like if you flashed in a new file when you change fuel. that has to be considered as well. thats why i told you to run through more than a tank after switching before logging.

Its good to know that the trims don't reset when doing map switching. I never really even thought about that. That's good info for anyone un - aware.