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Thread: How much OD can a M90 take?

  1. #1
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    How much OD can a M90 take?

    I was wondering how much OD a stock eaton M90 case could take, Im currently at 15% od (10% crank 5% blower) and I was wondering if after I mount the fmic if I could up the boost a little more and still be safe and relible? I have the raised sc top as well as alot of other boltons.

  2. #2
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    Quote Originally Posted by 90tbirdsc View Post
    I was wondering how much OD a stock eaton M90 case could take, Im currently at 15% od (10% crank 5% blower) and I was wondering if after I mount the fmic if I could up the boost a little more and still be safe and relible? I have the raised sc top as well as alot of other boltons.
    You didnt say if it was a 93 or earlier blower or a 94/95 blower regardless you are probably at a max on overdrive. The FMIC is a good mod but spinning the heck out of a stock M90 only makes huge amounts of heat that even a FMIC can only do so much with. The raised top will give you nothing for performance gains, they are expensive and look good but dont give measureable performance gains.

    Ken

    93 SC Whipple powered 11.648 @ 119.6
    Twin Turbo, air intercooled..yet to see

  3. #3
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    its a 90 and what If I add methanol injecton?

  4. #4
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    if you go back down to 5% as you sit right now, your car will be faster.

    10% and even 15% on a stock supercharger and stock intercooler will make the car feel faster at low rpm, but its creating so much heat you are not getting the benefits up top. Even with the front mount, 10% is about max. If you get a late model blower and magnum powers inlet, or go with an MPX case you will be able to run 15% and get the benefit.

    Also if you are still running stock 30 lb injectors and stock tune, your car is extremely lean on the top end. I wouldn't recommend running it like that.
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

  5. #5
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    so even if I upgrade the fuel system with 42# injectors and 255lph fuel pump and methanol injection 15% is still to much for a stock m90?

  6. #6
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    I ran 20% overdrive on a ported late model blower with a ported inlet plenum and made 269rwhp. Then I bumped it up to 30% overdrive and made 286rwhp. I had a fmic and was running e85 though.

  7. #7
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    Quote Originally Posted by 90tbirdsc View Post
    its a 90 and what If I add methanol injecton?
    5% until you upgrade the intercooler and then 10% after you also do some work to the inlet.

  8. #8
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    Quote Originally Posted by 90tbirdsc View Post
    so even if I upgrade the fuel system with 42# injectors and 255lph fuel pump and methanol injection 15% is still to much for a stock m90?
    The real problem with the early model is the inlet is so small it can't really flow enough air. The more you spin it, the more you heat the air, and the IAT can only tell the computer to compensate so much before it pulls timing up top. A front mount will help keep the intake temps in check and the 10% will be ok.

    If you can find a deal on a late model blower and inlet, then port that, spin it at 15% with a front mount, and get a used MP inlet you'd make great power.
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

  9. #9
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    I hate to keep doing what if posts, but I found a 1995 m90 off a sc that I could purchase. how much od with my custom fmic could I do? Im not really familar with porting superchargers, ive done a couple heads and it was just smoothing the ports out but then again im only 16

  10. #10
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    15% is a good number, however if you are on stock 90 30lb injectors you are going to max them out and lean out the car. I would look into a MAF and injectors also, unless you want to burn a hole through a piston.
    Scott Long
    1992 SC 5-speed
    Black on black leather, lowered, 18x9 Chrome Saleens...

  11. #11
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    Quote Originally Posted by Scott Long View Post
    15% is a good number, however if you are on stock 90 30lb injectors you are going to max them out and lean out the car. I would look into a MAF and injectors also, unless you want to burn a hole through a piston.
    An early model M90 can be ported and coated rotors can be added and coating to the case to reduce heat but all said and done its limitations are just too much. the only way to understand why is to look at the inlet on the back of the supercharger, it is oval and small. Be better off to add methanol injection and leave it alone or choose a new route on the supercharger.
    Last edited by davec73; 12-15-2012 at 12:37 PM.
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  12. #12
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    Cleared them out.
    Scott Long
    1992 SC 5-speed
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