Fuel cut, MAF overun or something else?

[Budget90GST]

I recently installed some fuel mods on my 90 gst. The list includes 190 lph, EVO8 560's, tuned with a MAFT on a 3" GM sensor (drawthrough). I also have a 2.5" turboback on stock 14b, 02 housing and manifold. I have all my intercooler pipes replaced with a 2.25" solid pipes with the stock sidemount intercooler. My question is, is it possible to hit fuel cut or MAS overun on this setup at 18 lbs of boost. The only other time I remember hitting fuel cut when I was stock was when I was setting my MBC and accidentally boosted it to 23 lbs. I can run 18 lbs but I seem to hit fuel cut at roughly 4500 - 5000 rpms repeatedly, usually higher rpms in higher gears. When I dropped the boost to 15-16 lbs, I was able to go all the way almost to redline. Oh, and I get maybe 4 to 5 counts of knock on either boost settings, leak tested to 20 lbs with no leaks. If I am hitting fuel cut, would raising my fuel pressure allow me to run 18 lbs all the way to redline. This is on a daily driver that will probably never see track time. I just want to be able to run 18 lbs and I'll be set. Maybe a supra sidemount in the near future then I'm probably done with her. What do you guys think? Thanks in advance.

 

[anconover]

your not overrunning a gm maft, its probly somewhere in your tuning, are you tuning strictly with the maft? What are your settings, and post a log if you can.

 

[Budget90GST]

Thanks for the reply. Yeah, I'm tuning strictly with the MAFT. I have it for 600 cc, idle 3, mid 3 and WOT 5. I don't have a current log but timing starts at 15 then climbs to 17 before hitting what I think is fuel cut. Knock is usually 5 to 6 counts and o2 at 0.8 ( i never had it higher even when richened to a point of studdering).

 

[anconover]

you richened up WOT 5 clicks? 5 clicks seems like alot, lean it out a little at a time, make sure to keep an eye on things, but see what happens and if the fuel cut goes away.

 

[Budget90GST]

Thanks. I'll give that a shot. With my 02 readings being all out of wacked, I'm afraid of running lean, but I guess I can gradually lean it out and see if that helps. Thanks again.

 

[anconover]

dont tune to o2's. My o2s read .76v, knock maxing at 3, timing around 17-18 on pump gas, 23psi. o2's can come in handy, but def not the basis of tuning. Knock and timing is what you have to be picky with.

 

[Budget90GST]

Just did a WOT pull with the WOT knob on 4 and i got 7 counts of knock on 2nd gear that faded to 0 on third gear. Timing went from 15 to around 19 till 5100 rpm on both gears. I'll get more into tomorrow durig the day when I can the road better, don't like doing WOT when it's fairly dark. Thanks again.

 

[nine5raptor]

Yeah, that +25% at wot is insane. If you need all 3 dials richened up by 15% or more, I would start back at scratch and get your base setup properly.

 

[Budget90GST]

I went and installed another fuel pressure regulator and reset my base. That was exactly my thought with 560's, I should not have to add too much fuel up top. I think my regulator was not rising with the boost so I replaced it and the tuning begins again. Thanks!

 

[nine5raptor]

hopefully it is that easy!

Glad to hear you (hopefully) got it figured out

 

[devioustsi]

I was just wondering if you got it all figured out? Also wondering why your using a gm maf as pull through? The main reason for guys doing the gm maf conversion is freeing up the intake track to the turbo, not just to vent the bov to the atmosphere. I have seen 20+whp gains by going to the blow through style. This is just a suggestion, since your under the hood soo much these days.

 

[yangtech]

wow... i must be running my car way lean than, cause my WOT setting on my MAFT is 3 click lean plus i also setting my injectors size bigger which it equals leaner too, but i got no knock and it pulls harder than when i have it rich. WTF

 

[devioustsi]

wow... i must be running my car way lean than, cause my WOT setting on my MAFT is 3 click lean plus i also setting my injectors size bigger which it equals leaner too, but i got no knock and it pulls harder than when i have it rich. WTF

What do your logs look like? What do your egts look like? It pulls harder because your actually burning all the fuel in the cylinder, but you might be running too lean.

 

[yangtech]

no knock on my timing and o2 reading is around .89, when i dont lean it out, it kind of just stumbles and run like junk.