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Discussion Starter · #1 ·
My 90 5.0 with the new s/c (6psi) I installed has brought back my dreaded detonation:

Question:

1. How do I enrich my fuel mixture/ratio, is this through an adjustable fuel pressure regulator? Even though I have all stock fuel system parts will and adjustable fuel pressure regulator still work?...How is a/f ratio measured exactly, can I do it myself?

2. I've backed my timing down to approx. 7* so I don't want to go any more, should I?

3. I've always run 93 octane and recently tried octane boost with no success, could this still be part of the problem...I can't imagine I need more octane since my car is stock with a low psi s/c kit but who knows???

4. I know a dyno is the best way to adjust/tune things but I am worried about some dyno tech raping my car to the point of failure...Is there a way they can simply tune the car without beating the hell out of it...I am not interested in having the perfect all max power tune at redline, I just want the detonation to stop...?

5. I have thought recently about carbon build up inside the intake/ect....I read an article online that talked about a 4.6 v8 with severe heavy load detonation but everything was within specs...It turned out to be build up in the intake...They did a 10 minute chemical spray job while it idled and the detonation was gone...Could this be it???..What would be the best way to do this...Is there a spray at an auto parts store that I can do myself...Is it safe to use on a s/c engine???

Thanks,
Jason
 

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No more than your building in boost and at that timing setting with 93 octane I am thinking you have additional parts that are weak. What fuel pump are you using?
What State are you located so I can figure your Altitude to figure your true octane rating.
 

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Discussion Starter · #3 ·
I'm in Louisville, KY...My altitude is approximately 500'msl...The guy I bought the car from about 2 years ago said that he recently changed the fuel pump before I bought the car...I have no idea what kind or volume pump he installed...Secondly something I forgot to mention is in 3rd gear or OD trying to push the car up at high speeds say 70-80 mph The car seems to surge/stutter/shutter...It feels as if it is starving for fuel but I am new to diagnosing this fuel stuff...What would be causing this surge?

Thanks, please others jump in on this

Jason
 

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Discussion Starter · #4 ·
Ok...Clint Walker on here who has been helping me through all this crap suggested cleaning the MAF sensor...I did a search on here for that and have found that lots of people have had the surging/poor performance/detonation problems I'm talking about and as soon as they cleaned the MAF it was gone...I have never cleaned it so I am going to do it first chance I get and will report back...I am thinking that my boost condition is only added to the problem if it indeed is dirty....I do remember looking at the sensor when I tuned up the car, but I didn't see that it looked dirty...Can it be dirty without any visible signs of such?????

Jason
 

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Discussion Starter · #5 ·
Hey can I enrich the mixture simply by removing the vacuum line from my fuel pressure regulator?
 

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fuel pump strainer could be dirty, fuel filter could be clogged. id rather be safe than sorry and order up a new fuel pump, 255lph and you'll have no problems
 

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Discussion Starter · #7 ·
Nails I see you have a 9psi kit on yours...So you really think it is my fuel pump not keeping up huh????....That is what it feels like with the erratic surging...I'll check and replace the fuel filter tomorrow, where is the strainer located????....I am in the process of getting an adj. fuel press. regulator with a press gauge mounted to it....I am planning on a dyno run to see what the pressure is doing under boost...But I would like to get the problem corrected as much as possible before the dyno run...Anyone else have any suggestions?

Thanks,

Jason
 

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the strainer is on the fuel pump itself in the tank. i recommend spending the $150 on a new 255lph in tank pump (holley, bbk etc.) and definitely the adjustable fuel pressure regulator. do you currently have an adj regulator? also what size injectors are you running? if you are running stock 19# with an fmu you have probably stressed the fuel pump too much by now. my major mods are listed in my sig, i am running a 255lph in tank pump w/42# injectors, 4:1 fmu, 80 mm maf. i just put the blower in and have had it running for a little over a week, i am a little rich at idle right now, just need to get mine on the dyno for final adjustments and make sure all is good on the top end
 

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Discussion Starter · #9 ·
Nails...what do you mean by I may have already stressed my fuel pump too much by now...I do not currently have an adjustable regulator...Everything is stock including the pump and my 19# injectors...I am running the supplied Paxton FMU...Not sure of what ratio that fmu is...Will just using the adj. fuel regulator allow me to richen up my mixture w/o getting a new pump too?...Paxton said I would be fine with my stock stuff, but I have been finding out I don't think they know everything they think they do...Please let me know..

jason
 

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the stock pump is good for 88lph @45psi (i believe) all you are doing with the fmu is increasing fuel pressure with boost. i believe the fmu for 19# injectors is 12:1, meaning for every one pound of boost generated fuel pressure is increased by 12psi, higher pressure does not mean higher flow on the fuel pump. all it does is make the pump work harder, if for example you are running around town smashing the pedal and making 4lbs boost, your pump is pushing 48 extra psi than its rated for, not long before the pump will fail. the manufacturer will tell you everything is ok because they market the kit as a bolt on complete kit. you should run codes on your engine, definitely get an adj fpr-right now you cant adjust at all without it-will allow you to fatten her up, new fuel filter, and i would bet your pump is a stock 88lph and has had enough. the pump i run is a holley 255lph forced induction pump (rated for use at higher pressures) and is $159.88 from summit part#HLY-12-915. a bigger fuel pump will just give you the constant fuel that is needed under boost, and its one part that will support future upgrades, better heads,cam, larger supercharger. hope this helps
 
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