Long term fuel trim bank

[b e z]

A guy said that anything 10 and up is cause for concern, so i set up my ltft on my ultragauge last night. While driving home on highway and it was reading 8.59 and 10.94. Then there were the random times it read 14 something. So can someone explain what this means and if i need to fix something to get these numbers down. Aslo my short term reads fine, anywhere from +/- 3. I did reset the ecu after the intake mod but didnt drive it like a grandma for 100 miles, but it has been at least 300 miles now so i would think its good to go now.

 

[b e z]

I think there is another ltft, i believe there is a 1 and 2 on the ultragauge and maybe i should monitor that as well.

 

[the_caruch]

were those LTFT values when cruising or WOT? what is LTFT when you are WOT?

I wouldn't worry about it too much if it's cruising. It's just running lean and is adding fuel to become 14.7 afr.

If you have the AP or standback you can adjust the MAF values to bring these numbers down.

Don't look too much at STFT, it's good for seeing if you have a leak. If they are wildly off like +/-25% then there is probably a leak somewhere. But STFT always varies and your 3% is more than ok

 

[b e z]

The random times the 14 percent popped up i think were when i was accelrating and it also stays at 14 when going wot in 2nd. I did read on here back in 09 when a bunch of guys were putting the cobb sri on they were having similar numbers so i have stopped worrying as much.

 

[the_caruch]

if it's +/-14% under WOT then your MAF needs calibrated. it's not good to be that off, especially lean.

 

[b e z]

how do you calibrate your maf?

 

[the_caruch]

i guess i should have asked, do you have the AP or SB to tune with?

 

[b e z]

Nope sure dont, i was about to say im sure you have to

 

[b e z]

i did read that a hypertech tuner makes the ltfts back to what they should be reading, dont know if that is 100% correct or not.

 

[b e z]

Also do you think it would make a difference if when i had everything back together shortly after i ended up getting on it instead of taking it easy for 100 miles.

 

[the_caruch]

i did read that a hypertech tuner makes the ltfts back to what they should be reading, dont know if that is 100% correct or not.

not 100% correct, it's not known how your car will react to an "over the shelf" tune. it could bring your trims back to an acceptable level, or it could shoot them way rich.

If you are considering a tuning device i would go with the AP or Standback. There are lots of threads comparing them, they are the 2 best tuning devices that are out now for the MS3 in my opinion, solely for the fact that you can customize your tune to your mods and how your car reacts. And not rely on pre-determined values that worked well on some test car.

Also do you think it would make a difference if when i had everything back together shortly after i ended up getting on it instead of taking it easy for 100 miles.

doesn't matter. it takes varied rpm/load ranges to get your fuel trims "learned" by the ECU. When i reset my battery, i drive like normal. i have my dashhawk there to let me know if something is going wrong.

 

[b e z]

Hmmm i wasnt planning on buying anything else for the car for a bit especially something that has the pricetag of an ap but that is the only to solve the problem i guess. Thanks for the info tho man

 

[the_caruch]

It's the only way to fix it. (among the tons of other great stuff the AP and SB can do to give more power)

If you don't want to drop the money for AP or SB, i would at least get a monitoring device like the Dashhawk to keep an eye on things.

 

[b e z]

I have an ultragauge so i can keep an eye on it like that i will just have to decide what i want to buy or which to buy.

 

[cclngthr]

At cruise the AFR should be around 14.7 or close to that. At WOT, the AFR should drop to about 12. Any lower, you are running too rich and you end up having raw fuel diluting the oil and ruining the cat.

If the AFR is above 15, you are going too lean.

 

[b e z]

I dont have anything that shows the afr, i will be installing a boost/afr this weekend tho but it wont show numbers it is a meter that goes to lean, rich, and optimal

 

[cclngthr]

I dont have anything that shows the afr, i will be installing a boost/afr this weekend tho but it wont show numbers it is a meter that goes to lean, rich, and optimal

The meter you have will show if it is going too lean or rich. When you are on the gas, it will go rich, but it is better if you know how rich it is getting. Optimal fuel AFR is what I posted.

 

[b e z]

Yea i would like a afr that shows the actual readout but i didnt buy that gauge just for the afr more so for the boost portion of it. I still think it will help to know at least rich,optimal, or lean

 

[b e z]

To add to this since i dont have a true afr gauge to read the 14:1 deal, i set up my ultragauge to read out the bank 1 oxygen sensor 2 voltage and it was reading at idle .77-.82, at crusing around the same numbers and at wot in the nines. Ive read this means its running rich, i dont know if it is really high numbers or not and i know our cars come stock rich but again to what point they are stock im not sure.

 

[8.5MS3]

spend the coin and get a dashhawk