WOT longterm trim keeps changing

[Coldandafraid]

After the ecu reset, high throttle was good at +8% fuel. After 2 days, that was rich, and I had to go to +7% fuel. 2 more days rich again, changed to +6% fuel. And on and on. right now I am at +1% fuel and have the same WOT trim as I did at he time of the reset and was +8%. So... I guess the longterm trim thinks I am lean or something and keeps adding a percent every couple of days... is this ever going to stop? And... what happens next time I reset... I have to go through this all over again?

Also... im not knocking at all... so why would the longterm trim change?

 

[Blk_99gst]

First your mods so other people know what you have:
Big 16G, 3" O2 Elim, Apexi FMIC, Keydiver stage III chip, GM MAF, S-AFC, 680cc Injectors, RX7 210lph fuel pump, K&N filter, Dejon intake and full IC pipes, Hallman MBC, HKS ssqv bov, Pocketlogger, 4 gauge ground wires.

Several things to start with. First off, fuel trims (stft and ltft) are not used at WOT at all. Those are used for normal everyday, closed loop driving. Second, what are you using to tune. I see youhave the gm maf, so you can be tuning with the translator, or the safc; and what's the stage III chip? Is that compensating for bigger fuel injectors at all? There is nothing wrong with have long-term-fuel-trim be + or - 5%. But if it keeps creeping up to +8%, then yes your low settings are a little lean and should be adjusted.

 

[Coldandafraid]

Ok. tuning with just the afc. Stage III chip compensates for injectors, that is why I am +fuel at WOT.

Ok... so I was wrong in saying that the long term trim changes. My Idle and low throttle is perfectly tuned. So... ignore that part of it.

But what I described is happening: At WOT, after an ecu reset, my high throttle setting on the AFC is tuned at +8%. Then, 2 days later that is too rich, it needs to be retuned to +7%. Then 2 more days it is too rich again, and needs to be retuned to +6%. 2 more days +5%. 2 more days +4%. 2 more days +3%. 2 more days +2%. Right now it is at +1%, and runs as nice as it did after the ecu reset/+8% fuel. So... during WOT, high throttle on the AFC, why does it get richer every couple of days. And, will I have to keep leaning it out to match?


Unrelated:
Also, when using the afc to tune, in relation to the perfect fuel curve... it seems to me that -1% fuel will knock 0% fuel will run good, and +1% fuel will stutter rich... should it be this precise... or should there be a bit more "slack" in the addition of fuel before rich stutter occurs?

 

[kpt4321]

There should be a whole heck of a lot more slack than that. A 1% change on the SAFC is going to be *approximately* a 0.1 change in the air/fuel ratio, which is fairly minor. It should be more than 10% between knock and rich stutter.

How are you determining that the hi throttle settings are too rich?

Your post is very confusing because you referred to a "WOT longterm trim." Nothing of that sort exists.

After you reset your ECU, has your long term fuel trim (LTFT) changed at all? I think that the LTFT is going to have somewhat of an effect on the level of enrichment at full throttle, even though the ECU is not in closed loop there.

 

[Coldandafraid]

Actually I think I have figured out the problem. I thought I was rich stuttering... now I am almost certain I was blowing out the spark with too much boost/bad wires. Because I lowered the boost, and the car is SO much easier to tune, and yes, there is a lot more slack in the lean - rich stutter fuel difference. SBR COP is on the way.

As for the WOT changing... its now been at +2% for 5 days... and looks like that is the magic number... why it "seemed" to be changing on me, I dont know.

 

[white 2g awd]

got the same prob as you bud, i have the injector comp, and i have it leaned out like hell now, and its still running rich i guess, i just don't understand.

Dustin

 

[Coldandafraid]

what boost are you running. Try what I did, and lower the boost to 15 (if you are above that) Maybe you are blowing out your spark plugs and that is what is causing the stutter.

 

[white 2g awd]

i'm only running 10 psi, creeps to about 19 at 7k, but i hope that a 16g wouldn't blow out properly gapped spark plugs at this low of boost...even so, its just a 16g...

Dustin

 

[1fast97gsx]

what boost are you running. Try what I did, and lower the boost to 15 (if you are above that) Maybe you are blowing out your spark plugs and that is what is causing the stutter.

I've never heard of blowing out spark at boost levels that low .. but what can you do if you really are blowing out spark?? I'm having problems with my turbo (scm61 @ 21 psi ) and I think I might not be getting proper spark or blowing it out or something as well.

 

[Coldandafraid]

yeah, thats what people told me as well... that the stock ignition should be fine fr 19 psi... but lets pretend that the tuning is perfect, the fuel supply is perfect, no boost leaks... why else would it stutter at 19 psi, but run perfect at 15 psi... I might have bad wires, either way I ordered an SBR coil on plug setup, so, ill make sure to report back... I wont change anything, Ill just plug in the COP and raise the boost back to 19 and if the stutter is gone, that was the problem.

 

[kpt4321]

A stock ignition in good shape should not only be ok for 19 psi, it should be ok for 25 or 30.

If it is the ignition, then yours is broken.