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  1. #1

    Desparately seeking 700 rpm

    OK guys, I got an issue here. I have an 07 rxt with the following mods (x-charger with upgraded washers, 42's, rude rrfpr x intercooler with riva mod, 15-20 4 blade, x waterbox with freeflow exhaust, riva intake grate, 2 degree pump wedge, riva 3 inch intake, 82mm nozzle).

    Ran the ski and there was a little chop. 84 degree water temp (almost year round)

    Best speed as 66.2 at 72-7300 rpm. Hookup appeared good but rpm planed out on topend)

    I know I can change the nozzle to a bigger one. Also may need to check charger slip (I assumed ok because it was recently rebuilt by Jerry).
    Also know that increased water temps means decreased performance.

    Any other advice. Riva stage I ran 66.1 previously.


  2. #2
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    4" intake, did ya have a boost gague or check for boost leaks?

  3. #3
    speedskixp's Avatar
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    Have you checked your A/F? Are you sure you have 42s and not 50s?

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    1) what is your base pressure for the RRFPR?
    2) GET RID of that 3" intake, its choking that X SC...
    3) The 15/20, is that straight out of the box or is it used?

  5. #5
    Quote Originally Posted by Danny View Post
    1) what is your base pressure for the RRFPR?
    2) GET RID of that 3" intake, its choking that X SC...
    3) The 15/20, is that straight out of the box or is it used?
    Base pressure is 60, and I checked afr's and they ranged about 11.4-11.7, best that i could see while riding. They are 42's (stock green injectors with X-boat)

    Brand new 15/20 prop.

    No boost gauge hooked up.

  6. #6
    How big do you think the nozzle would have to be to get the rpm's up reasonably, say another 4-500 rpm's.

  7. #7
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    U positively have an issue somewhere, I ran basically that same setup and was good for 74.5mph in 95* air and 82* water, on a rxt, i would look at all ur IC lines and clamps, also get a boost gauge on it cause u will never know whats going on with out one, should see around 10.6 out of that charger at about 8000 rpm, u have the right prop thats for sure, stock nozzle is the way to go unless ur looking for more take off then go bigger, I would also get ur slip checked cause thats what was causing me to loose RPM's big time by the end of the summer i was down almost 500 to 600 RPM the slip was at like 6lbs.

  8. #8
    speedskixp's Avatar
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    Quote Originally Posted by comish71 View Post
    Base pressure is 60, and I checked afr's and they ranged about 11.4-11.7, best that i could see while riding. They are 42's (stock green injectors with X-boat)

    Brand new 15/20 prop.

    No boost gauge hooked up.
    11.4 is really rich. adjust for 11.9-12.0. You will gain some rpms there but not all of them. Also ditch the 3in air for 4in as others mentioned. Also put the stock nozzle on or 83mm ring. See where you are after this and go from there

  9. #9
    GOT BOOST? Dockside's Avatar
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    Check for boost leaks and upgrade to a 4in as stated above

  10. #10
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by speedskixp View Post
    11.4 is really rich. adjust for 11.9-12.0. You will gain some rpms there but not all of them. Also ditch the 3in air for 4in as others mentioned. Also put the stock nozzle on or 83mm ring. See where you are after this and go from there
    Remember, your AFR is going to change once you get your rpms up to 8,100 rpm.
    You do look to rich, I would quess but that is at 7,200 and 8,100 so will vary.

    I would do as speedskixp, stated and you need to start testing and rulling out issues.
    You need to be sure what slip is on charger.
    lower fuel, and see what afr and rpm, go up on nozzle size.

    What prop did you run with your stage 1?

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