SAFC fuel problem

[Gottiboy]

1998 gst lots of mods but...
550cc
I have to have my safc turned all the way up to %30 just for car to idle and not run lean. I know with bigger injectors I should be in the negatives but car won't even run with settings even at zero.
Car also won't rev worth a dang up to around 2500 rpm. After that it seems to run good.any ideas?

 

[Gottiboy]

20g precision turbo
550cc
Fmic
Apexi safc
Greddy turbo timer
Greddy electronic boost control
Greddy bov
Some pcv setup I've never seen

 

[pauleyman]

Are you sure those are 550s? What about fuel pump or fuel pressure? What have you checked?

 

[Mello]

What are you using to measure your AFR's?

 

[Gottiboy]

Not sure on the 550cc. That's what I was told. I just bought the car 2 weeks ago.will check fuel pressure tomorrow and report back. Unfortunately I am using narrowband o2 sensor currently to monitor AFR.
I figured sense it runs better after 3k rpm low fuel pressure wouldn't be the problem.

 

[Gottiboy]

Are you sure those are 550s? What about fuel pump or fuel pressure? What have you checked?

How can I tell what size injectors I have? I'll check fuel pressure at work tomorrow.

I've checked all safc wiring to the ecu. Set my tps to spec.checked timing with timing light. The car idles great. Have not done boost leak test but have checked and tightened all fittings. Had a MAF sensor connection issue but fixed that. Checked all grounds. I'm really stumped. Because no matter what size injectors it has as long as they are larger than stock I should be using negative corrections on the safc

 

[Gottiboy]

still need help with the SAFC settings. have worked out alot of bugs. know alot more about the car now too. but even tho i dont know what size injectors i have there is no reason i should have to have the afc turned up past zero for it to idle right.deff not all the way up to plus 34% for it to idle.
have wally 255 pump (confirmed now)
installed a AFPR (set to 43 with vaccum line off)
mechanical timing is on point
tps set to factory spec
no leaks

 

[lasershark]

You really need to verify the size of your injectors. Try to get a look at the brand and or the numbers that are on them. Can't take somebodies word on injectors especially if you are having issues like this...

 

[Gottiboy]

i do need to know the injector size but no matter what size they are i should never have to have fuel turned up to +34 just to idle and not be leaned out.
that is unless someone put smaller injectors in the car wich can not be the case. cuz when the 20g spools my af goes all the way rich. smaller than stock injectors would not support 20psi on a big turbo like this.

i really wish someone had some answers

 

[Dstarperformance01]

So, you bought it with this issue and all add on's or did you put injectors,safc,etc?

 

[Dstarperformance01]

Also, I thought a narrow band O2 shouldn't be used to tune with, I could be wrong! I remember when I had just a narrow band the gauge would always read from rich to lean back and fourth because your short term fuel trims(idle)differ from long term trims(cruise,acceleration, and deceleration)

 

[boostdawd]

U really need to find out what parts your car has. Guesswork and tuning are a bad combination. I understand what u mean about the +30 in adjustment. Take a glimpse on the wiring for the safc. Make sure everything is hooked up correctly and tight. Check your ecu as well for signs of leakage as this may be the culprit.

 

[Mello]

I'm thinking you don't have 550cc injectors. From what you're saying I'd suspect your injectors may be from an auto DSM which are smaller 390cc than the manual OEM injectors. This also would make sense of you having to add 30%. Can't believe what people say especially when trying to make a buck.

 

[Dstarperformance01]

That's what I was thinking too. Or it's an auto ecu maybe?

 

[Mello]

Auto ECU would cause the opposite & he'd be adjusting negative to keep from being to rich.

 

[Dstarperformance01]

I'm sorry. You are correct. I meant a manual ecu with 390's. That makes more sense

 

[Gottiboy]

I'm gonna pull the injectors this weekend. I drive it daily and the o-rings look shitty so I wanna have new ones when I take the injectors out. Someone has scribed or drimmle some writing on each injector. Can't make out what it is until I get them out tho. I love this car but it's driving me crazy!! Lol

 

[Dstarperformance01]

Cool. Let us know what you find. We are happy to help. Do you happen to know what brand they are?

 

[Gottiboy]

Is this the right ecu for 98 gst 5 speed?

 

[Dstarperformance01]

Not sure. Looks like a 1g but don't take my word for it. It looks like an EPROM ecu. Open it up and post a pic

 

[Gottiboy]

Cool. Let us know what you find. We are happy to help. Do you happen to know what brand they are?

I do not. I will have full details tomorrow and I really appreciate the help guys

 

[Gottiboy]

Hell with it I'm gonna go pull it right now sense u guys are here helping out

 

[Dstarperformance01]

 

[twicks69]

Is this the right ecu for 98 gst 5 speed?

That has a 1994-1995 manufacture date which is typical with EPROM 2G ECU's; as well as it had the "E" in the bottom corner. Opening it up would confirm if it's an EPROM.

The original ECU would be MD346675 for 1997.07 - 1998.05 build date and MD359402 for 1998.06-1999.04 build date.

 

[twicks69]

please take pictures of the injectors you have in the car, or remove them and take detailed photos.

Do you have a stock or aftermarket fuel pump? Fuel filter? Adjustable fuel pressure regulator? What's the condition and wiring of the mass air flow sensor? Are you recirculating the bov or venting?