more boost, more problems

Discussion in 'Fox 5.0 Mustang Tech' started by daemion_AF, Dec 18, 2003.


  1. daemion_AF

    daemion_AF New Member

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    Well i put a 12lb supercharger pulley on yesterday, replacing the 6 lb pulley. Holy crap is the car mean now, but i have some questions about a few things. It seems like there is some sort of limiter, 1st gear boost stops at 9, second stops at 12, third stops at around 16, and then there is fourth... Fourth gear the car stutters really bad at WOT and the check engine light comes on until it hits around 12 lbs and then it feels like something kicks it in the ass and then the tires break loose. My air fuel ratio gauge seems to think im not having any problems but something has got to be wrong. I used the original belt for the 6lb pulley and it doesnt fit on there very tight, but it works...could the belt be slipping and causing this? BTW i know its to much boost to run on stock internals but its around 20 degrees outside so that definately helps. Any suggestions are welcome, thanks.
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  2. TIMMY2734

    TIMMY2734 Founding Member

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    I dont think your belt is the culprit. Did you change the FMU disk?
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  3. Iowa91LX

    Iowa91LX Founding Member

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    Are you sure its the correct pulley? A 12lb pulley should only produce 12psi, why is it reaching 16psi in 3rd? The varied boost problem most likely is from belt slippage. Changing pulley sizes that far you need to get a different belt.
    With my old 12rib Procharged setup I could hear the belt slip over the gear driven head unit and X pipe. Plus the accesories on the front of the motor got covered in black soot from the belt slipping.

    Check your fuel system out too, it being 20 degrees outside is already enough to make the car run lean. Your now doubling the boost and adding 50+rwhp which is going to take a lot more fuel.
    Dont rely on your airfuel ratio guage to tell you everything. They are not very accurate, and IMOP a waste of money. Call some dyno shops that have a wideband and ask them about your airfuel ratio guage. They wideband is the only way to be positive.
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  4. daemion_AF

    daemion_AF New Member

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    I havent changed the FMU disk out yet, dont have a replacement...prolly gonna order one pretty soon. Also someone told my my 65mm TB may be to small or to go with plugs 2 ranges colder and gapped at .30. It got around 60 yesterday and the car was stuttering really bad, even worse than before. Not to mention the belt is slipping now...
    #4
  5. JadeFalcon

    JadeFalcon Founding Member

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    Alright, I've been there done all this.

    1) First of all, your A/F gauge is NOT how you judge your cars performance, you can stare at those pretty lights while your motor dismantles itself under the hood. You sound like your having belt slipping problems, it is normal not to get full boost in first, because your belt slips since it has to accelerate so quickly. second to third really shouldnt be a big difference in boost. 16lbs of boost on a 302 is where you crack the block in half, 20 degrees outside isnt going to save **** when that happens, hehe. 16lbs of boost is just too much, you need to back off to no more than 13, 11 is where you should stick.

    2)What this REALLY sounds like is spark getting blown out... Don't tell me your running stock plugs... if you are, goto step 3.

    3) YOU IDIOT! You NEED 2 step colder plugs, your blower is BLOWING the spark out!!!
    #5
  6. Iowa91LX

    Iowa91LX Founding Member

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    What is your plug gap set to? I had mine initially set to .55 and once I put the charger on I set them back down to .35. It will stumble and stutter if your blowing the spark out. Close the gap down to around .35 and see what that gets you. You may want to but a set of new plugs with a shorter ground strap than stock, that will help you out.
    Another word of advice...... Stop driving it until you get your problems worked out. Your probably well on your way to melting pistons, or blowing a head gasket if you havent already.
    #6
  7. daemion_AF

    daemion_AF New Member

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    I actually pulled the supercharger pulley yesterday, im not sure if its got the stock plugs or not i havent really had the car long enough to know how the previous owner took care of it. Im on my way home for christmas so ill prolly put the new plugs in and try it out back home. As for the belt slipping i bought a new tensioner pulley that is a little beefier than the plastic pos that came with it so im gonna give that a shot when i get home also. Anyone have any idea what type of diaphragm i should order from vortech for the FMU without knowing what is previously on it?
    #7
  8. stangbear427

    stangbear427 Active Member

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    A wastegate/blowoff valve is cheap insurance too- even for a supercharger, although nobody in the supercharger world likes to hear it. The lack of one isn't your problem, but you wouldn't have to worry about blowing $#i+ up because you found yourself spiking to 16lbs.

    p.s. Anybody here know of Jim D'Amore? Ford Lightning tuner guru and the second Terminator owner in the country to go 10's? At the time he had only ONE (1) one aftermarket gauge in the Cobra's cockpit- an air/fuel ratio meter. Not so much as a Monster tach. Not a $560 Uego 1000 wideband sensor, just a 2&1/16" Nordskog pod gauge. So why all this trashing of them? If someone doesn't know how to read one and all it is to them is a light show, then I suggest they either learn how, or shut up about them? Obviousely it isn't just a gimmic, when one of the most respected forced induction tuners in the country finds them to be a necessity in his supercharged projects. Granted, I don't think not knowing how to read it is your problem either, or that your A/F ratio even necessarily has anything to do with it, just couldn't let that mud keep getting thrown without opening my big mouth. :bang:
    #8
  9. TIMMY2734

    TIMMY2734 Founding Member

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    But if his belt is slipping, wouldnt he be making less boost? Thats the way i see it at least
    #9
  10. stangbear427

    stangbear427 Active Member

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    It wouldn't be causing it to produce more boost, but it would keep it from hitting full boost as fast or as smooth as it should- stuttering, etc. The driveablilty issues mentioned. I'm a little surprised that a 12# pulley is cranking out over 12# of boost at all though, with or without a tight belt. Either the pulley isn't really a 12#'r, the vaccuum gauge isn't accurate, or somehow the other pulley ratio's have thrown the rpm's of the blower way off. None of which would really explain the driveability problems though. His overboosting situation isn't what he's complaining about, I don't think- but yeah, you're right.
    #10
  11. daemion_AF

    daemion_AF New Member

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    Overboosting isnt my problem i'd just like to keep it from stuttering so badly. Another thought, with my 6 lb pulley i was hitting 9 lbs in all gears....so it wasnt just swapping the pulley that overboosted it. But anyways i will try the plugs out tomorrow and see what type of fmu diaphragm i need and see if this works.
    #11
  12. stangbear427

    stangbear427 Active Member

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    I think you need to double check your vaccuum pressure with another gauge- I can't believe you didn't grenade the stock bottom end in a mystery maintinance engine with 16lbs of boost- I think you're boost gauge is lying to you. Again, not that this is addressing the problem you are threading; just a nagging observation that is raising some ?'s in my head here. For instance, if you have any idea how to drive the car with that list of mods you should be deep into the 12's at least. I can out run your best 13.7's all day with my N/A combo which I consider to be pretty mild; 9lbs of boost should give you way over 100HP more at the crank. Something doesn't add up here, and it just begins with the dubious boost readings. Sounds more to me like you've got an honest 5lbs of boost and must be spinning rubber like mad 'till you cross the finish. What gives?
    #12
  13. blown1989saleen

    blown1989saleen Founding Member

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    i agree that A/F gauge ISNT gonna tell you anything ACCURATE, you gotta remember when you take a big jump in boost like you did you gotta take measures to be sure the motor is ready for that boost jump, lower timing, be sure the fuel is there. and as stated the cold air actually leans your A/F, ive noticed from 50-60 degree air to 30 degree air my AFR's go slightly leaner on my WBO2, so dont be fooled there. it seems like your getting some belt slippage causing the boost fluctuations, and it seems like your other problem is spark blowout, or your going extremley lean and causing the stuttering, either way make sure the car is ready for the big boost numbers or your gonna be replacing blown HG's
    #13
  14. daemion_AF

    daemion_AF New Member

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    As surmised i pulled the plugs and found that they were the stock heat range and were gapped at .45, so im betting money it will run a little better under boost with these new plugs gapped around .35 to .38. Not to mention the plug was reddish in color almost like rust, so it was prolly running really hot and lean. Im also with stangbear on this one, a 13's seem really really easy to some of you N/A guys and this car has got some really sweet mods which makes me think something is not right. The only thing i can say in its defense is that i ran at about 7000 ft above sea level at a crappy little track in far west texas on street tires. Another thing, last night i ran a monte carlo SS without the charger on and after i ran him you could smell antifreeze from inside the car. I popped the hood and you could smell it even worse but no leaks or anything were noticeable. The "check oil" light came on so i checked the oil for the milky look a blown HG would give it but it seems fine.
    #14
  15. rustang94

    rustang94 New Member

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    I have a friend with a 96 gt with a vortech and his car would stumble and stutter just like yours. He called vortech and they told him to gap his plugs at 35 and its been fine ever since...
    #15
  16. stangbear427

    stangbear427 Active Member

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    Not to mention the crank, rods, pistons, block...

    As for the antifreeze smell, if it doesn't appear to be leaking under the hood have you considered a heater core problem? Just a thought, since you can smell it. Check your passenger side carpet on the firewall and under the floor mat and make sure it's dry.

    For your times, extreme elevation would explain a bit. At 5000', that would bring you down to a corrected 12.76 at about 108mph at sea level- which sounds a lot better, if still kinda slow for your parts. That's also assuming we believe in correction factors- particularly when forced induction is involved. But on that train of thought, 7000' would be even faster, but that brings up another off-topic question: I'm no geography major, but 7000' above sea level in Texas? Are you serious? I didn't know there was any land that high in TX. Are you pulling my leg? Regardless, you aren't as slow as you sound, which is a good thing.

    Out of curiosity, you said your A/F meter says your ratio is where it belongs- which brand are you using and what exactly is it doing at WOT? Do you have a fuel pressure gauge in the cockpit too? What's your pressure set at, and if you have one, how high does it spike at WOT? Between the slipping belt and this new revelation about your plugs and gaps, I suspect the problem is pretty wrapped up; I'm just wondering about this stuff, in the event that you feel like pacifying my curiosity.
    #16
  17. JadeFalcon

    JadeFalcon Founding Member

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    So let me get this straight, your keeping the stock plugs but gapping them less? You need 2 step colder plugs, if you don't take the advice, good luck... Definately not worth the time to explain why you need them.
    #17
  18. Trboh22

    Trboh22 Member

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    When you have open open exhaust, you will get more boost than if you have stock exhaust, because there is less restriction, which explains a 16 #'s of boost and a 12 # pulley.
    #18
  19. daemion_AF

    daemion_AF New Member

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    I went down 2 heat ranges in plugs, gapped them at .35 and they were doing wonderful. I used some belt dressing and had a friend hanging off of the tension which kept the belt from slipping for a while. But later during the day it started to slip again so i just pulled her till i can get a new belt. With regards to stangbear, im in odessa TX right now which is around 3500 feet or so. The track is a ways northwest from here straight up the caprock, everyone says its around 6500-7000 but after researching it for you im pretty sure its around 5000 to 5500. The A/F im using is an APC, i know its gay but a sunpro, and an autometer one wouldnt read correctly. Towards mid throttle without boost it reads as rich as it can, WOT it slowly works its way down to stoich as the boost climbs. I dont have a Fuel pressure gauge but there is a mount on my fuel rail already so im prolly going to get one, im curious to see what it is with the T-Rex fuel pump.
    #19
  20. stangbear427

    stangbear427 Active Member

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    Sounds like you're leaning out as more air gets forced in, which isn't uncommon without swapping the FMU. It isn't good either. I wouldn't trust an APC meter, but what it's telling you is that your fuel injection system isn't being given the right orders from the computer, or the pump can't keep up (which should NOT be your problem). You definately don't ever want to see a stoichometric readings at WOT, especially when the boost is really slamming. You'll have holes in your pistons in no time. The more air you force in, the more fuel you need, and the more spark you need. Getting the right belt on there will smooth out your boost cycle, putting in the right plugs and closing the gap will handle the extra spark you need, but you are starving it for fuel if your A/F ratio isn't staying full rich as long as you're at WOT. Your fuel pump isn't what determines how much pressure you have, your regulator does, in conjuction with your computer. Getting an adjustable FPR will allow you to give it what it needs; the stock 38psi definately isn't enough for any boost, never mind what you're running. Having the right chip for your boost level will do the rest.
    #20

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