What does an FMU do for a supercharger system?

Discussion in 'SN95 4.6L Mustang Tech' started by DC-GT, Dec 9, 2003.


  1. DC-GT

    DC-GT New Member

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    I was at a shop today asking some questions and he said that he would control the fuel air mixture with an FMU (Fuel Management Unit). It somehow measures pressure from the air and multiplies it for the fuel? I am sure that is lost in the translation...

    So how does it work, and is there a better way to do it?

    Bo
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  2. Aaron 4.6

    Aaron 4.6 Founding Member

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    An FMU increases fuel pressure in proportion to boost. Thus a 4:1 FMU will increase fuel pressure 4 psi per pound of boost. This is a poor man's way of compensating for increased cylinder pressure, but it is not a very accurate way of tuning a car, and in order to be safely rich across the RPM range you usually end up with some VERY rich fat spots in the fuel curve.

    There are much better ways to set up your fuel system, and I thought FMUs were for return-style fuel systems anyway (which an 03 GT does not have)
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  3. DC-GT

    DC-GT New Member

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    Your right, the 03 does not need it. I did some more research and I made a phone call or two. The 99 and up Mustangs don't need it. They have a fuel management system already installed.

    Bo
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