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  1. #1

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    Point SC Boost Kicks In ?

    04 GTX SC 185HP

    I read through a few threads in the SD and other forms about gas milage. A number of posters said they 'Kept off the boost" and got so and so gas usage.

    At what point is the SC Boost on ? MPH or RPM ?

    I assumed that the SC always provided some boost. Does the ECU map change the fuel output at a this "boost point" ?


  2. #2
    The supercharger boost is always on and is a direct relationship to the RPM'S of the engine. In other words, there is no "boost point" for the ECU to deal with.

    CWI

  3. #3

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    Uh......... What is the MAP sensors function (mass air preasure sensor). I always thought it relayed the presure in the intake to the ECU and the ECU managed fuel and ignition based on readings from it and other sensors.

  4. #4
    You are correct. The MAP sensor is a dual function sensor that measures intake plenum and barometric pressures and relays that info back to the ECU. I don't think that is what Piney is asking. He's asking at what point and time does the supercharger boost "come on" and the answer to that is that it is always "on" if the engine is running. The more engine RPM'S...the more boost. There is no certain RPM or MPH that the supercharger "kicks in".

  5. #5

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    Your absolutely right. That did get me thinking about issues with using say a rude 3 on a rec sled. If your capable of producing 13-15 pounds of boost at 8100 and have the RIVA ECU/ valve train upgrades ect. Cruising at 73+ at 8100 and partial throttle must really be hard on the SC drive train and clutches.

  6. #6
    I don't know much about the high performance stuff. Isn't there a blow-off valve that is supposed to take some of the stress off the SC? Does it come into play at partial throttle or just when you chop the throttle?

  7. #7
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    Quote Originally Posted by CWI View Post
    There is no certain RPM or MPH that the supercharger "kicks in".
    Wrong!

    Quote Originally Posted by CWI View Post
    I don't know much about the high performance stuff.
    Your making that obvious.


    The boost is not always on! Until you hit around 5000 RPM... the intake is still under vacuum, the boost will start to rise from zero around 5500 RPM... and will continue to rise up to max RPM. Ideal cruising speed for fuel economy is at zero vacuum - zero boost.

    Blow-off valves have never been factory installed from BRP on the 4-tecs.

  8. #8
    I understand what you're saying and I was incorrect to say that there isn't a boost point for the MAP to deal with. My point was that the SC is always creating pressure and is not something that is being turned on and off as needed.

  9. #9

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    WIth my Rude 2 and eteck s/c the boost starts at 6100 rpm's and rises as rpm goes up. I didn't have a gauge on the boat with the stock s/c- .02

  10. #10

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    Quote Originally Posted by CWI View Post
    I understand what you're saying and I was incorrect to say that there isn't a boost point for the MAP to deal with. My point was that the SC is always creating pressure and is not something that is being turned on and off as needed.
    If I understand what BigDaddy wrote, there is no Sc boost until 5,000 rpm because there is no vacuum until that point.

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