Help! SCT tuner mistake

[encasedmetal]

I was referring to the fuel trims (adaptive learning) in my original post. That's why I said stft and ltft. Fuel trims are the correction being made to keep stoich, you have it backwards. What did you read?

There is no way your stft and ltft are only varying 1%.

The OP has all the signs of an improperly scaled maf xfer function. More than likely his tuner used the value file and left it. When the car was on the dyno the fuel tables were adjusted to get commanded lambda instead of fixing the maf xfer.

why would you say there is no way? on a highly modded car 6% is alot. and I know what you were saying to begin with. I agree with maf xfer being off, however, when the OP moves to closed loop I do not agree that stft and ltft should be as far out as 6%- that's just inefficient and lazy IMO. but then again I am constantly get my maf xfer table exact to the 10th decimal. that's just me.

 

[BruceH]

why would you say there is no way? on a highly modded car 6% is alot. and I know what you were saying to begin with. I agree with maf xfer being off, however, when the OP moves to closed loop I do not agree that stft and ltft should be as far out as 6%- that's just inefficient and lazy IMO. but then again I am constantly get my maf xfer table exact to the 10th decimal. that's just me.

I say no way because they constantly change to maintain stoich. It's quite normal for them to fluctuate from - to + in correction.

I monitor mine constantly via interceptor gauges and like you I have my maf xfer tweaked as good as it gets. The trims still move around especially during varying throttle positions and loads. At idle with a fully warmed up motor my trims don't move more than .01 (1%) but during normal driving they will change. In order to have 1% your trims would read .995 to 1.005 and the long term trims would be at 1.00 using an sct device. On my interceptor gauges it would be - .5 to +.5 as it reads no change as a 0 vs 1.00 during an sct datalog.

Fuel injectors have an allowed tolerance of 6% from most manufacturers so even with a perfect maf xfer there will still need to be a fueling correction made. That 6% isn't going to be linear either, it will show up at different points throughout the rpm range. Gasoline will also vary. Think of the difference between pure gasoline with a stoich of 14.64 vs. E10 at 14.1. Then add in "up to 10% ethanol" and you could have anything inbetween. The ecu is still going to maintian the stoich commanded in the tune no matter what the fuel. This will cause trims to vary too.

With all that said keep in mind I'm just a hobbyist and tune my own car to keep my mind occupied, I really like the learning aspect of it and enjoy discussing all the parameters involved.

 

[encasedmetal]

I say no way because they constantly change to maintain stoich. It's quite normal for them to fluctuate from - to + in correction.

I monitor mine constantly via interceptor gauges and like you I have my maf xfer tweaked as good as it gets. The trims still move around especially during varying throttle positions and loads. At idle with a fully warmed up motor my trims don't move more than .01 (1%) but during normal driving they will change. In order to have 1% your trims would read .995 to 1.005 and the long term trims would be at 1.00 using an sct device. On my interceptor gauges it would be - .5 to +.5 as it reads no change as a 0 vs 1.00 during an sct datalog.

Fuel injectors have an allowed tolerance of 6% from most manufacturers so even with a perfect maf xfer there will still need to be a fueling correction made. That 6% isn't going to be linear either, it will show up at different points throughout the rpm range. Gasoline will also vary. Think of the difference between pure gasoline with a stoich of 14.64 vs. E10 at 14.1. Then add in "up to 10% ethanol" and you could have anything inbetween. The ecu is still going to maintian the stoich commanded in the tune no matter what the fuel. This will cause trims to vary too.

With all that said keep in mind I'm just a hobbyist and tune my own car to keep my mind occupied, I really like the learning aspect of it and enjoy discussing all the parameters involved.

I am impressed- and think that we are on the same page actually, I mistakenly took your statements too generally and I apologize.

 

[J's98Snake]

Please, bear with me I new with this tuning stuff. me being a dumb@$$ i decided to screw around with the tuner about three weeks after i bought the car. AFR's were right around 10.9-11.2 at WOT. Now they are running at like 12.4-13.3 w/ the 3.5 pulley..... It has a pre-loaded tune on it for a 3.25 pulley (check mod list below). Im wondering how bad i could have screwed it up because it does feel a little different..... I tried to get the datalogging set up but its not letting me do it for some reason. I dont have a tuner anywhere near here thats any good. So i guess my question is will it be ok running the "3.25" pulley tune if i just adjust the WOT Air/Fuel to 14% richer or do i need to trailer it 600 miles back to salt lake city and have the people who built the motor tune it????

Dont know if it has anything to do with the tune but at start up the intake sounds like its sucking in MASSIVE amounts of air. Idle's fine.

Any help or advice is appreciated :beer:

drive straight down 95 to Vegas and see Carl at Dynojet, he'll tune your car to perfection.

 

[SicilianMobster]

Ill see if i can post a video of what its doing pretty soon. Cars been down a couple of months and im kind of scared to drive it knowing that there might be something wrong.

If i could get my datalogging working i heard that there are some tuners online that do "lifetime tunes" for pretty cheap. Would that be the best for my car (mod list below) and my wallet? Sorry, like i said i havent the slightest clue about tuning (probably something i should have considered before buying such a highly modded car.)

 

[SicilianMobster]

could something have happened with my BAP????

 

[Swervedriver]

Yes. The pressure switch could have gotten hot & started leaking. The hose could have split or popped off.

Take the 2 wires off the pressure switch and short them together. This will run the BAP full time. See if that makes any difference to your AF readings.

I also cannot stand CPR rails. Seen them push injector O rings down & spray fuel too many times. Not that I think that has anything to do with your current issue, just a warning.

 

[SicilianMobster]

I also cannot stand CPR rails. Seen them push injector O rings down & spray fuel too many times. Not that I think that has anything to do with your current issue, just a warning.

Shit happens all the time...... I swear autozone keeps the o-rings in stock just for my car..... Def. looking to get rid of those f'in things this summer