Help Tuning FP BIG 28 w/ SAFC and Logger

[dbzpat]

I have a 95 GST and I recently installed the BIG 28 from Forced Performance, my mods include: Greddy Type RS BOV, OBX FMIC, Injen Air intake and Filter, Megan Cat-Delete Downpipe, 3" Cat back exhaust, NGK BPR7ES Plugs and NGK Wires, FIC 550cc Injectors, Walbro 190lhp fuel pump, Voodoo MBC, FP Big 28 Turbo, and Apexi S-AFC. Currently I have the turbo set around 20psi, the car seems to run well but at high RPMS 4500-6500 it will occasionally shake violently like I am experiencing fuel cut, but I know I am not because my logger readings are not lean. My question is may i be getting to much fuel? I currently have the high throttle percentage at -14% on the S-AFC and my logger fluctuates on the fuel trims from -6% to 15%. Or does anyone have some S-AFC settings that I could use as a solid baseline while am getting my car fine tuned?

 

[2gGSX]

I have a 95 GST and I recently installed the BIG 28 from Forced Performance, my mods include: Greddy Type RS BOV, OBX FMIC, Injen Air intake and Filter, Megan Cat-Delete Downpipe, 3" Cat back exhaust, NGK BPR7ES Plugs and NGK Wires, FIC 550cc Injectors, Walbro 190lhp fuel pump, Voodoo MBC, FP Big 28 Turbo, and Apexi S-AFC. Currently I have the turbo set around 20psi, the car seems to run well but at high RPMS 4500-6500 it will occasionally shake violently like I am experiencing fuel cut, but I know I am not because my logger readings are not lean. My question is may i be getting to much fuel? I currently have the high throttle percentage at -14% on the S-AFC and my logger fluctuates on the fuel trims from -6% to 15%. Or does anyone have some S-AFC settings that I could use as a solid baseline while am getting my car fine tuned?

Unless you have a wideband output wired into your logger, those AFR readings mean nothing--there are large fluctuations between what front O2 voltage corresponds with what AFR, and thus no way of safely predicting it.

Have you checked your plug wires? What about spark plug gap? If you're already at .028" then try to move it down to .024" and see if that helps.

Your STFT should fluctuate around 0, and your LTFT should be as close to 0 as possible. What is your LTFT reading at?

 

[Polyol]

I'll tell you one thing you sould'nt be running 20 lbs. until you get you tune right

 

[Polyol]

Your setup is pretty close to mine. I had a hell of a time tuning with the afc. I finally got a wideband and found out i was running very rich, after about 6 months of trying to tune w/afc, and the car running differnt every time I drove it sometimes it would run great other times it would run like crap "pig rich". So I finally purchaced a keydriver stage III chip burned for my 550's & socketed eprom. Now it runs great every time. A wide band helps alot for tuning

 

[dbzpat]

My LTFT is at +12

 

[e36bmer]

With more severe mods like that it will be much easier to tune with a better piggyback/ standalone or through chip tuning. I have never liked the SAFC for tuning.

 

[-TunedDSM-]

I would start out at a lower boost level (14lbs or so) and slowly work your way up. It will help you get the hang of adjusting fuel trims and is alot safer than just jumping to 20lbs. Just my two cents, good luck!

 

[JayRolla]

I also think you should buy a wbo2. Its the only way to get a good tune, the logger is pretty much guessing.

 

[turboboy4]

I would cut the boost back to about 15, until you get a decent tune. I would purchase a key diver chip burned to your set-up and that will help alot in getting your tune close.

 

[Zmann42087]

Not the cheapest thing, but you could just take your car to a shop that offers dyno tuning with a wideband O2 service. They could definitely help you nail down your tune.

 

[dbzpat]

I called the local performance shop, and they said they would not touch it unless it had a wideband. So I recently ordered the AEM Uego, I am going to use that and try to do it on my own, if not, then I guess I will call them back.

 

[Zmann42087]

I called the local performance shop, and they said they would not touch it unless it had a wideband. So I recently ordered the AEM Uego, I am going to use that and try to do it on my own, if not, then I guess I will call them back.

Yeah, thats understandable. However, a lot of shops that offer dyno tuning provide a wideband O2 sensor for the tuning session. In other words, you don't have to necessarily own one.

You might want to look around a little bit more and see if you can't find a shop that does dyno tuning with a WB O2 service.