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blow thru w/ SAFC and 750cc injectors... what to do?

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MC23

15+ Year Contributor
45
0
Feb 8, 2004
hampton, Virginia
Alright i got done building my 2.3 about the end of may. Had a lot of problems with spark knock and bought 750cc injectors( to rich after installed). Just bought a SBR FMIC w/ blow thru set-up and have a AEM UEGO installed. Here is my problem, I had the 750cc in and was really hard to start. Shooting a lot of rich fuel, so i put in the stock 440cc in and of course adjusted the MAF-T according to size. Then disconnected the SAFC intercpeting signal (thinking that it was screwing up the signal from the MAF-T). My Ratios would start at 15.3:1 and climb down to 10:1 + and they were there to stay.

This would continue with every adjustment made with the MAF-T. At this point im am ready to pay someone fairly to help me out. Also i was following directions with MAF-T. Tried to lean it out on the SAFC and all of that. Im still tinkering with it and need a lot of help, someone with GM MAF experience would be great. Thanks guy and sorry for making this so long!
 
I too am interested ever since I put in 750s it is hard to start and I also have a safc, maft, and stage 3 chip.
 
750ccs are "kinda" big for an SAFC.

Try this - turn all your settinsg on the MAFT to zero, including the injector scale knob and then tune with the SAFC.
 
i'll try it.... another thing is my light for the MAFT is blinking 7 times (which means something about "noticed an engine reset")
 
Alright i tried it and still nothing better, I forgot to add in that my car sounds like it is miss firering and will sputter when i touch the throttle. (note im on stock injectors right now).
 
yep done all of that... plugs were super black from the richness
 
Where on the plug was it super black? Idle A/F on a plug is on top of the porcelain. 750s and SAFCs don't mix too well, though I run a NT reg. and denso 660s with MAFT and SAFC and the car idles/starts fine. Your best bet is to get a chip to compensate for the 750s. You can lean the shit outta it at low throttle but thats just somewhat of a bandaid, may not help much either. The MAFT is worthless when it comes to tuning IMO. Don't touch that thing, just tune with the AFC.
 
Do you have a logger?.I used this method with a logger.Dial the injectors on the maft till the short O2 trim level will flutter around 95-105.Long term should not be changed no more than 90-110.I have 660cc with a keydiver chip set for 660s and the maft liked 420cc settings.That should get you started.;) And the car will "buck"when trying to boost if the A/R is too rich.Sounds like backfires.Oh the back oh mine was almost on fire .:p
 
miragetbo1997cc said:
Do you have a logger?.I used this method with a logger.Dial the injectors on the maft till the short O2 trim level will flutter around 95-105.Long term should not be changed no more than 90-110.I have 660cc with a keydiver chip set for 660s and the maft liked 420cc settings.That should get you started.;) And the car will "buck"when trying to boost if the A/R is too rich.Sounds like backfires.Oh the back oh mine was almost on fire .:p

Thats my issue right now... I put stock MAF back in and just crusing around with that for now untill i get an EPROM with keydiver Stage 3 chip. Ill keep you guys updated thanks for your help!
 
The first time i installed 780-750cc injectors with a maft blowthru set up with non eprom ecu, car ran fine after dialing in the preferred settings. Your problem could be your settings, tune or leaks.
 
Mr.Tao said:
The first time i installed 780-750cc injectors with a maft blowthru set up with non eprom ecu, car ran fine after dialing in the preferred settings. Your problem could be your settings, tune or leaks.

Yeah i checked for more leaks after driving last night (note: i changed back to stock 440cc injec., stock maf, and disconnected SAFC) and some of my IC pipe clamps were leaking and i got little tiny leaks coming from the manifold bolts. Now the car runs better but still wants to run rich( 10.1: 1 ratios) under WOT.
 
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