Ford Mustang Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
1,626 Posts
Discussion Starter #1
Well heres the scoop... 94GT aode,Stock, heads/cam/intake/t/b, 9lbs vortech supercharged, 12:1 FMU , AFM power pipe, 3.3"/7" pulleys.. full exhuast, walbro gss340 pump, and bbk adjustable fuel presure regulator..

Well it seems, from looking at the plugs that i have been getting a slight bit of detonation.
(i have heard it ping once or twice, in high 3rd gear, under 8lbs).. but i let off as soon as i detected any ping. That would probably explain the spotting on the plugs... Other then that they dont look to be carbon, or oiled up... Funny thing is, my car seems to be running very rich.. so why arent they plugs black, if its running so rich. Base fuel presure varies from 47psi to 50psi..
WOT presure is usually around 85psi. Top end doesnt seem to be running overaly rich or anything.. actually feels right on. its just down low, its like its running pig rich, i get some surging, stumbling, and hesatation(like its running too rich)... Then agian, what gets me is why my plugs dont show a rich condition..
Although my tailpipes have always been really black with carbon buildup... I dont know, what the deal here is... Ide like to get it running decent, the way it sits now...then in time, pick up a
Pro-m77 meter, 42lb injectors, an inline pump, and get a good safe tune...

Heres the plugs, just as they came out...


 

·
Registered
Joined
·
550 Posts
To me those look very lean. They look like you just took them out of the box. I'm no expert on plug reading, but I've always been told that a good looking plug should be the color of light to medium toast.. You know light to medium brown. To me those seem very white, which in all intents and purposes usually means too lean.:confused: Anyways back to the top...
 

·
Registered
Joined
·
1,145 Posts
Those plugs actually look pretty normal to me, but Im no expert. My question to you though, is why is your base FP set so high? The way you have it set up, your car must idle pig rich, and then it would tend to go lean up top. Your computer's going to compensate by leaning it out. You should set your base fuel pressure to whatever your stock pressure is - prolly 38lbs. THe best thing you could do if you dont want to upgrade your injectors to 42's and ditch the FMU(recommended), is go get a dyno tune and have them look at the AF. Then they can adjust your FP and FMU to put it all together. Good luck
 

·
Registered
Joined
·
1,591 Posts
Your base pressure is to high. Thats why it feels like a pig in low rpms. The plugs look just new to me, prolly getting to lean at the top end..I would not run 19# injectors period:eek: Your detionation Up top is prolly cause its lean. I cant see the ground strap very good but look at that it will tell you how much heat is in the combustion champer.. If its starting to turn blueish there is to much heat and you need more fuel or less timing or both..
 

·
Registered
Joined
·
1,626 Posts
Discussion Starter #5
the presure is so high, becuase i can not turn it down any more..
Ever since i installed this Walbro gss340( high presure) pump, the fuel presure has been off the wall. I try to turn the presure down, by turning the set screw out, and it seems to have no effect on presure. it still stays at 47-50psi... i try to turn the screw in, and it stays the same. This regulator is fairly new... (BBK) and i dont think its bad, but then agian it could be for all i know. its been fine this whole time... up till the new fuel pump.

. I cant see the ground strap very good but look at that it will tell you how much heat is in the combustion champer
By this do u mean on the plug its self? the tip that extends over the electrode? That isnt blue... The plugs have around or less then 1000 miles on them... and they still look new, just like thast came out of the box... not white, not oily, not black, not brown...
 

·
Registered
Joined
·
1,145 Posts
If you cant turn down your pressure on your BBK (I have the same one) then its defective :eek: You should be able to control that pressure. Are you checking your pressure correctly - with the vacum removed and plugged? Why not try your stock regulator? The 2 pumps you have help each other out, that wouldnt make for uncontrollable FP.
 

·
Registered
Joined
·
1,626 Posts
Discussion Starter #8
u have to remove and plug the vacuum line to check presure?
If so, then i have been checking presure wrong this whole time. I hope its somthing stupid like that, and not a defective regulator.
Do i remove the vacuum line to check idle and WOT presure, or just WOT? Also i only have one fuel pump... its the GSS340.. no inline. I also noticed, when looking at my rail mounted BBK fuel presure guage, it reads much higher then the cowl mounted, autometer guage..
Therail mounted guage fluxuates from 55-60psi (idle)... Same time the rail mount guage is reading 50-60psi at idle, the cowl mounted autometer guage is reading 46-48psi...
Now i dont know which one to read, or which one is correct, cuase both are giving me diferent readings..
Odd thing is, this all started when i installed the new pump.
I do have the stock regulator laying around, so i can try that tommaro hopefully.. and i am running 8+lbs..non intercooled(Vortech) most of the time at 5500rpms i see 9lbs.. almost 10
 

·
Registered
Joined
·
1,145 Posts
When you remove the vacuum and plug it, you a reading the pressure you will have at WOT. This is tested at your fuel rail test port. Your idle FP is set by your computer, and its based on the WOT setting. You should see around 30-34psi at idle on your cowl meter.
Since you're running no intercooler, you definately will need to retard your timing. Only safe way is through a tune.
 

·
Registered
Joined
·
1,626 Posts
Discussion Starter #10
ok thats what i thought.. vacuum off is WOT presure.
I know the computer on 94-95's adjust the fp..
But 30-34 seems alittle low with a blown car, specially since stock is around 37psi. I would atleast like to get the idle presure down to around 42 or 40psi. Also, i am running with the timing bumped down... its at 7* now without the BTM
 

·
Registered
Joined
·
1,145 Posts
Your car's gonna prolly run like butt with the idle set at 40-42 though. You dont need that much.
 

·
Registered
Joined
·
1,591 Posts
poostang said:
ok thats what i thought.. vacuum off is WOT presure.
I know the computer on 94-95's adjust the fp..
Umm, dude,.....The computer has nothing to do with fuel pressure!

Just thought you might want to know..
 

·
Registered
Joined
·
1,145 Posts
94BLOWNCOBRA said:
Umm, dude,.....The computer has nothing to do with fuel pressure!

Just thought you might want to know..
Thats correct, but I think he meant that the computer will compensate for too much pressure by leaning out by way of the injectors (which the computer DOES control). FP doesnt mean anything when the injectors dont allow enough fuel. Fp does not dictate to the computer how much to flow - the MAF does that.
 

·
Registered
Joined
·
1,626 Posts
Discussion Starter #15
sorry i wasnt SO descriptive with what i was trying to say..
But yes, Tat98Cobra, said exactally what i ment..
 

·
Registered
Joined
·
1,145 Posts
Cool
Let us know how you make out!
 
1 - 16 of 16 Posts
Top