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  1. #1
    SHIFT's Avatar
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    Stock rxp with S3 charger?

    Hey i searched around for this but the only hint of information i got was from the mods database,

    if i got a S3 charger on my rxp aswell as the 3inch intake (with a intake grate and 14/19 prop already installed)
    -what size injectors would be best? 42s or stock?
    -at the moment im seeing 7800rpm on a cold day so would that be enough prop for that setup?

    im hoping this would be a safe and reliable setup as i have seen a rxp-x on a trailer the other day and im starting to get worried if there is a time i meet one on the water
    thanks!!


  2. #2
    speedskixp's Avatar
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    I would go with the 42's to be on the safe side. You should be able to add an external IC and still be safe in the warmer months.

  3. #3
    West Texas RXP skoepp's Avatar
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    42,s should work. take a look at my thread "tested new mods with results" . I ran 42s with S3 with good success.

  4. #4
    Moderator Snoman's Avatar
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    You could also install a Rising Rate Fuel Pressure Regulator and keep your Stock injectors..You might be a tad rich running 42s with no external IC...

  5. #5

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    Yea the S3 with the stock IC is borderline. I think it would be ok on the stock injectors. I don't think the 14/19 will be enough prop though. It may take some serious bending or a 15/20.

  6. #6
    speedskixp's Avatar
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    Quote Originally Posted by Snoman View Post
    You could also install a Rising Rate Fuel Pressure Regulator and keep your Stock injectors..You might be a tad rich running 42s with no external IC...
    Maybe a little rich but we set-up a boat with that exact same set-up and 42's to be safe and it ran great. better rich than lean. If was flying blind I would go on the rich side. It all depends on the RAD in your area. I would go with the rrfpr if you plan on upgrading the charger later on or if you want to get A/F gauge so you can dial it in for WOT.

  7. #7
    SHIFT's Avatar
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    Yea i want to aviod the intercooler, because to get the pirahna you need to change the exhaust then probably change the opas then change the sponsoons and its all too much fiddling around. I want something more simple..

    Apparently running 42's with a external intercooler and s3 you will be rich at mid-low range, but is there a downside to being a little bit rich? I know being lean will burn your exhaust out.. The a/f gauge and fuel regulator is also too much fiddling for me.

    What do you mean it depends on the RAD?

    Maybe a greenwheel and 3inch air would be a safer (but slower) option

  8. #8
    Moderator Snoman's Avatar
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    Quote Originally Posted by SHIFT View Post

    Apparently running 42's with a external intercooler and s3 you will be rich at mid-low range, but is there a downside to being a little bit rich?
    No 42s and an Internal IC (Stock IC) could be a tad rich..Running a external IC,42s with your S3 could put you a tad lean...Its better to be a tad rich than lean..Downfalls would be a little more fuel consumption..Depending on how rich you could wash out your cylinders and foul out plugs...

  9. #9
    speedskixp's Avatar
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    Yes the 42's will be a little rich at idle and mid. Wont hurt anything.

    Basicly you RAD(reative air density) is the deciding factor on how much power your engine will make depending on your enviroment. The more power you are able to make the more fuel you need. Maybe Skoepp will post a link to the RAD calculator for you as I dont have it on this computer. If your rad is not good then the stock injectors should be fine. specialy running stock exhaust along with stock IC. A few guys have ran the stage 3 with stock injectors and stock IC but I think some of them may be a tad lean. IMO.

  10. #10
    Do the external IC. Its a cheap mod and it will make a huge difference.

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