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Thread: questions on a sn92 need help asap!!

  1. #1
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    questions on a sn92 need help asap!!

    well i have always been in to nitrous and i got a coupe now and my buddy has a sn92 blower i can pick up. a few things i want to know to better myself on them.....

    what is there max boost?
    what size fmu do u need for stock injectors?
    what size fmu do u need for 24 or 30lb injectors?
    what power gains would i see with a sn92 on a stock 88 notch motor with headers h pipe cat back?
    what gears would i run?
    what size pulleys make 6psi?
    what size pulleys make 8psi or more?
    what do i need to watch out for on a sn92 as far as keeping up on it things to do and not to do.
    can a power pipe be used?
    has anyone ever put a sn92 on a stock non mass air car and if so what did it make for boost hp and 1/4 mile if you ran it.
    and how much should a nice sn92 blower complete kit polished go for? j/w

    i dont think this blower is anything crazy but i am just looking to have fun it is a daily driver but im not afread to turn it up. well any info stories etc will be great so i can understand what i will be getting in to. thanks

  2. #2
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    Standard impeller on a stock motor, anything over 7 or 8 pounds is more heat than charge...

    14:1 for 5 pounds boost is Paxton's supplied FMU calibration for 5 pounds...

    C'mon do the math, it ain't hard: Boost pressure X FMU rate = targetted max psi. Use the fuel system calculator on Mustangworks if this is hard...

    300-350 horse @ 5 psi, given the condition of the motor under the blower...

    Whatever makes you happy, I have 3.55s...

    C'mon, do the math, it ain't hard...

    Keep the fluid clean with regular changes and a power pipe or some such can be used but is unnecessary in stock applications.

    I run SD. I last 1/4ed the car when the blower was busted and needed rebuilding. 4 pounds boost pushed the 3350 pound hatch to a 13.0 at 107 mph on wasted slicks. That's ~320 horsepower on an engine that already had blown head gaskets, too.

    It'll go for what people will pay. Polished is standard for the SN blowers, not an option. I'd pay no more than $1000 for a complete setup, and it would have to be mint, given how much new blower pricing has gotten aggressive.

    The up side of the old Pax is it is perfectly suited to the stock or near stock 5.0 engine so it's not so peaky like "entry level" blowers today.

  3. #3
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    hey thanks for the help so what is a 12:1 fmu for? j/w cuz i can get one for a good price and i think the kit needs a new one cuz the one now leaks a little

  4. #4
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    12:1 is Vortech's setup for their A-trim blowers on stock engines. They blew 6 pounds in that configuration.

    You know you can just change the calibration disc inside an FMU to whatever you want, right?

    F=MA

  5. #5
    SCH Moderator "SN Guru" speedytang's Avatar
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    You can also purchase from Vortech a rebuild kit for your FMU and they sell that kit also with a new calibration disc as mentioned.

  6. #6
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    so can i put on a vortech 12:1 and run 5-8psi with my sn92 and it will work good? how much is a rebuild kit and that stuff? and i prob sound stupid but i dont know this supercharger stuff.....what pulleys make what boost and this blower and what should my fmu be at for like 6psi and then for 8 ? mre you tell me the better. thanks again

  7. #7
    SCH Moderator "SN Guru" speedytang's Avatar
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    The FMU is based on injector size not your boost level. The stock crank pulley 6" and a 4.25" blower pulley will produce 5psi

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    so if i wanted more boost then i leave on the 6" and put a bigger or smaller blower pulley?

  9. #9
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    You are heading for a head gasket blow or engine meltdown. You need to get your knowledge ducks in a row before you play with this stuff or you'll be learning how to rebuild engines.

    Yes, you can spin the blower faster and produce a more boost, and a smaller blower pulley will do that. However, you must fuel for that additional air. The injectors will only handle so much before they are undersized, regardless of FMU ratio. 6-7 pounds in the upper limit for 19 pounders, period.

    F=MA

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    so what pulleys make what boost? on the blower i mean what are the sizes to boost? and also the fmu should be 12:1 or 14:1 for stock 19s and like 6 maybe 8psi and one more thing if i put in 24's what should the fmu be set at, o ha one more thing do u need to change the timing and fuel pressure with this blower like nitrous?

  11. #11
    SCH Moderator "SN Guru" speedytang's Avatar
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    At 5psi you can set your timing at 10 degrees and you will be fine unless your injectors lock up from 100psi being pushed on them. This is the reason a FMU is a risk because of the high pressure being forced on the injectors. If your going to change injectors go with 36lb units with matching MAS and be done with the FMU or if you get a tuning device(PMS, Tweecer, Chip etc.) then go with 42lb injectors. 3.75" with the 6" crank will give you about 8psi but you might run into belt slip on a 6rib at WOT. Anything over 5 psi and you will want to limit total timing at 24 degrees till you can use a A/F to verify.

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    SCH Member Nutzy19's Avatar
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    Last edited by Nutzy19; 07-29-2005 at 09:18 AM.

  13. #13
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    well i got it on i just need my fmu rebuilt or get a new one and put the tube from the charger to tbody, now where do i put the timming and what plugs do i us and what gap? i think there is a 6lb pulley on now not sure will find out when i start it i guess lol but let me know about the other things thanks for the help everyone

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    o yea i forgot one more thing what fluid do i put in there? and where can i get it part store? or i have to order it from paxton?

  15. #15
    SCH Moderator "SN Guru" speedytang's Avatar
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    Type 'F' transmission fluid.
    Set timing at 10 deg. with the distributor plug out.
    Use Autolite #24 at .035 gap

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