General Fuel Trims Stuck at 140%

[805eclipse]

Here are my car specs: 91 GST FWD 5spd, 650cc injectors, SAFC2 @ -25 across the board(needs to be tuned), UICP, Hacked MAF, Intake Pipe, EGT gauge, Boost Gauge, Dual Stage Manual Boost Controller LOW: 10 High: 15.

Ok so i hook up my Datalogger and log the Fuel Trims, RPM, Knock, And Timing. I dont know much about tuning so i figured id hook everything up and give it a shot cuz i got to start somewhere. But all my Fuel Trims are stuck at 140%, What makes this happen i know im suppose to tune for 100% but they wont move. At about 4,500 rpm i start getting knock and it hits max about 19 knock at 6000 rpm and timing is in the 20s. What im really worried about is how do i get my fuel trims unstuck??? if you have an answer for me let me know. thanks alot.

-Mike

 

[spoolup]

when they are at the limit they tend to stick. You might need to reset the ECU (disconnect the "-" battery terminal for a minute) and try again. you mention that the SAFC is at -25, is this the high or low setting? And did you adjust it according to the various tunning guides? Here are a few:

http://www.dsmtuners.com/forums/showthread.php?t=58403
and
http://www.roadraceengineering.com/newafc.htm

But try reseting the ECU and following one of the above guides and lets see how she acts. patiance since the fuel trims move slowly, espically in a 1G.

 

[805eclipse]

i have the afc set to -25 high and low just so i could drive it.. i will try reseting the ecu and tuning it thanks

 

[spoolup]

sounds like the better thing to do. I remember when I had a SAFC I never had a perfect flat line on the sliders, more of a arch starting high and working lower. With 580s I dont think my low a idle was -25, maybe thats why the fuel trims are stuck. I am not fimilar enough with 1G ECUs to know about their fuel trims, but if it read 140 I belive it may be adding as much fuel as possible to compesate for someone leaning it out too much at the 1000 RPM slider. Just my idea, but again I am not that fimilar with 1Gs.

 

[TURFNNSURF]

805eclipse,

Your LOW settings on the SAFC are to low for daily driving. -25 for any rpm over 2000 is taking to much fuel away from the closed loop operation of the ECU. here is my suggestions for LOW and HIGH settings on your SAFC to see if thinks get better.

LOW 800 1200 1800 2400 3000 3600 4200 4800 5400 6000 6600 7200
-15 -15 -12 -10 -10 -8 -8 -8 -8 -8 -8 -8

HI 800 1200 1800 2400 3000 3600 4200 4800 5400 6000 6600 7200
-15 -10 -12 -15 -18 -18 -15 -15 -12 -12 -15 -15

RE-set your ECU then try these settings, you'll have to drive your car for a few days so that the MID & HI fuel trims start to change. Keep in mind that your LOW settings on the AFC are what affect the fuel trims in your ECU. The HI settings on the AFC affect how your car runs at WOT/Open Loop. Since you were seeing knock onset at 4500rpm, I gave you settings to raise the amount of fuel your car uses from 4200rpm up.

Make sure you read Definitive Piggyback Tuning Guide by kpt4321 noted in the post above by Spoolup

I hope that this helps, if you have any other questions feel free to PM me.

 

[805eclipse]

Turf i did what you said and set it like that and reset my ecu and logged it, all the fuel trims started off at 100 and slowly the mid fuel trim rose back up to 140 and the other two are still at 100, does this mean im to rich and need to lean it out?

 

[Talonman]

140 means ecu is adding 140% and trying to add fuel (the extra 40%) so youre too lean not too rich.

 

[TURFNNSURF]

Your MID fuel trim is still to lean. 140% is lean. Try setting the LOW fuel on the SAFC more toward 0 between 2000rpm and 3500rpm. Those rpm's should be the range that you normally drive in, like cruising on the highway. Or just driving around town. You'll need to add fuel in the low settings till the trims stay near 100% (-/+10%) I try to keep my fuel trims as close to 100% as possible so the ECU doesn't have to compensate as much.

Here is a pic of my logger from tonight after reading your post.

You must be logged in to view this image or video.