Setting up my S-AFC

[QuickSilverGSX9]

Alright, I have a 1991 Eclipse GSX with some basic modifications. Full fuel side of things, Walbro 255 hp lph, BR/SX AFPR, and 680cc injectors. Anyways, I decided to actually go back and re-tune everything now because its pretty damn cold and because I installed an EVOIII 16g.
Now, I went out and plugged in my pocketlogger and started looking at my fuel trims and airflow at idle. My correction values were around -15% across the board on Lo. However, my low fuel trim was pegged at 139%, so I started enrichening things slowly, until I reached right around 100% on low...weird thing is, I'm now at +/- 0% across the board on Lo. That seems awfully strange with my setup, I'm running 680cc injectors with a MAS that only has the lower honeycomb removed..as far as I can remember the screw is still in it's stock location as well. That's not the only thing that's weird as well, with my original correction values on low (-15%), and even more leaned out on the Hi table, my High fuel trim was pegged out at 82%, in other words very rich.
I'm still starting from scratch from the S-AFC tuning guide I have, getting my fuel trims back to around 100%, but I don't know if I have a problem that everyone else will recognize right away or not. It just seemed strange to me my fuel trims seemed to be so out of whack. Thanks for your time.
-Bill

 

[kpt4321]

Don't worry about it. Follow the guide and do what the logger tells you to do.

It's normal for the lo throttle corrections to start higher than you expected and then taper down on a 1g. You'll never have it linear with a hacked MAF.

 

[QuickSilverGSX9]

I've noticed that while driving my low fuel trim may drop to as low as 90%, and then it raises all way up to 110% when I stop, say at a light or go to park or whatever. Is this kind of fluctuation normal? However, after letting it idle for even just a minute it settles at 103%, which I figure is alright for now. Thanks for the reply.
-Bill

 

[kpt4321]

That's fine. See where it is in a few days, but I bet it's fine.

Check for boost/vac leaks too.

 

[QuickSilverGSX9]

My vac. seems to be decent, sits at 20. Now all I gotta do is get my exhaust manifold and o2 sensor ported so I don't creep like crazy on the EVOIII 16g. Once again, thanks again for the reply kpt4321.
-Bill

 

[HighPSI TSi Guy]

it's normal to run kindof rich on the low end.. the load there is minimal, so really you don't have to add that much fuel if you don't want to... at -15 you also have some room to go leaner...

 

[QuickSilverGSX9]

I'm slightly confused on what you mean there Dave? With -15% on the Lo table, I was extremely lean, my low fuel trim was at 139%. I had to enrichen it up until my settings on the Lo table were +/- 0%, in other words, no corrections at all, to get close to 100% on my low fuel trim. So, I don't think there was room for me to go leaner. If you're talking about on the Hi table where there is quit a bit more load, then yes possibly there is room to be leaned out, I will have to do some actual tuning when I get the porting I need done. It's pointless to try and tune when anything above 5 grand I start creeping to insane boost levels.
-Bill

 

[kpt4321]

Just do what the fuel trims tell you to, don't worry about it.

When you port, make sure you do the WASTEGATE EXIT AREA. it is by far the most important porting you can do.

 

[HighPSI TSi Guy]

Originally posted by QuickSilverGSX9
I'm slightly confused on what you mean there Dave? With -15% on the Lo table, I was extremely lean, my low fuel trim was at 139%. I had to enrichen it up until my settings on the Lo table were +/- 0%, in other words, no corrections at all, to get close to 100% on my low fuel trim. So, I don't think there was room for me to go leaner. If you're talking about on the Hi table where there is quit a bit more load, then yes possibly there is room to be leaned out, I will have to do some actual tuning when I get the porting I need done. It's pointless to try and tune when anything above 5 grand I start creeping to insane boost levels.
-Bill

with the hacked MAF anything is posible.. if you are too lean then you are too lean.. the fuel trims only really govern very low airflow anyways.. the only time that the low trim is used once you start messing with the signal is going to be idle.. high and occasionally mid is what you'll end up using on cruise.. as long as the fuel trims are within adjustment range, and you don't get any knock, then you're fine.. you can get a little better gas mileage by putting it on the lean side slightly if you want.. if you're getting decent cruise mileage, no knock, and car runs smoothly, you are ok... i was at around -22 +/- a few on the SAFC when i was running an identical MAF to what you have.. so its definitely possible -15 is good for you..you should definitely be leaner than 15% on the highs.. also what do you have your fuel pressure set to?

 

[ITSME4G63]

Um, my fuel trim the top one on the pocketlogger is 139%, that's not goor right? what does that mean? I'm running lean? I have about -18 going from 3k+ on my high throttle setting and the low throttle is left at 0.

 

[HighPSI TSi Guy]

Originally posted by ITSME4G63
Um, my fuel trim the top one on the pocketlogger is 139%, that's not goor right? what does that mean? I'm running lean? I have about -18 going from 3k+ on my high throttle setting and the low throttle is left at 0.

reset your ECU and try again..

it all depends on your setup

 

[ITSME4G63]

Originally posted by HighPSI TSi Guy
reset your ECU and try again..

it all depends on your setup

small 16g, uicp, 550cc injectors, upgraded fuel pump, hacked mas, k/n filter.

 

[HighPSI TSi Guy]

with those settings you shouldn't be running lean unless you have a really hacked MAF... is your O2 sensor working?

 

[ITSME4G63]

Well, i just installed a new one 2 months ago
the a/f gague isnt fluctiang for shit but the pocketlooger shows the voltage fluctuating when the car starts warming up. Very few times do I see it stay at 0v.

 

[QuickSilverGSX9]

kpt4321, if you could take a look at my thread in the Problem Diagnosis thread about my injectors, I would really appreciate it. I'm pretty much at a loss and I think it could be a seriously problem possibly.
-Bill

 

[QuickSilverGSX9]

I swapped ECU's with my brothers, because his engine is being rebuilt right now. I no longer throw the injector circuit code error, however, after over 100 miles of driving and the ECU being in the car for several days, my fuel trims will NOT move.

I assume this isn't normal, even if I swapped ECU's? I let the car idle for 15-20 minutes as well and messed with the AFC like I did on my original ECU and nothing happened, the o2 trim seems to jump between 100-160% but I've never looked at it before so for all I know that's compeltely wrong.

I'd really appreciate some input, because I may just have simply traded problems by switching the ECU.
-Bill

This is simply copied from the problem diagnosis thread, however, I thought someone might be able to shed some light on why my fuel trims refuse to move...even after driving the car so much. I'd really appreciate any input.

 

[kpt4321]

In 2 days, they might not move. 1g fuel trims are TEH SUXZOR.

 

[QuickSilverGSX9]

Thanks for the reply kpt4321, I hope it is just the fact that 1g fuel trims are ###, because...if they're not, I'll pull my hair out in frustration.

Off topic, I used valvemedic by Gunk to clean my not-so-long-ago-cleaned lifters, and I believe that it's cleared it up the tick nicely. Just wanted to throw that out there. Thanks for your time.
-Bill