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  1. #1
    Jarrett's Avatar
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    RXP-X - Need some help

    Having a weird issue on my ski and wanted to see if the forum could help me solve it.

    All tests done on the same lake:

    Mods: 4" intake - Worx grate - Solas 15/22R - Free Mods
    Air: 99 - Water: 89 - Humid: 35% - Fuel: 2 bars - RPM: 8020 - Speed: 71.8
    Completely heat soaked engine

    Same mods, but much better weather on a cool engine
    Air: 70 - Water: 84 - Humid: 70% - Fuel: 2 bars - RPM: 8060 - Speed: 72.9
    30 degrees less air, cool engine, 40 RPM? But 1.1 MPH as well?

    Then added throttle body mod and removed intake manifold filter:
    Air: 78 - Water: 78 - Humid: 85% - Fuel: 4 bars - RPM: 8040 - Speed: 71.1
    Much cooler air and water, but again similar RPM and the ski slowed down. Also didn't feel as responsive.

    I'm having trouble understanding why the ski goes the same RPMs with different mods and in drastically different air/water temps. And also how the same RPMs with the same pump setup yields different speeds.

    First of all, is the tach accurate on these? Is there any chance the ECU retards timing and limits the RPM to the 8040 range somehow? I changed the oil at 10 hours, but didn't take it in for the 10 hour maintenance. Is there any chance its limited until it hooks up with BUDS again? Boost leak? Not sure what to think on this one.


  2. #2
    REID2168's Avatar
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    look at the humidity and air temp combos in your posts there in lies your own answer........just cause u feel better breathing in water in the air doesnt mean your boat does......test again when u got mid to low 70's air and 50% or less humidity and then report back!

  3. #3
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by REID2168 View Post
    look at the humidity and air temp combos in your posts there in lies your own answer........just cause u feel better breathing in water in the air doesnt mean your boat does......test again when u got mid to low 70's air and 50% or less humidity and then report back!
    +1

    Jarrett there is a calculator that you can figure your Relative Air Density (RAD)
    You need to monitor your barometric pressure, temp, humid, and you will see how it changes the RAD.
    I always look for pressure above 30.0 to have air and good test.

    As far as the limiter on the X, my findings are that the rev limiter will put you below 8,100 rpm very easy. I dont like the limiter on X as it will fool you very easy. You have to play with throtle at wot and you will see that the ski will hit max rpm before full pull.

    By the way your test results look good, just need a beter day.

  4. #4
    Jarrett's Avatar
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    Quote Originally Posted by skoepp View Post
    Jarrett there is a calculator that you can figure your Relative Air Density (RAD)
    Where can I find this?

    I'm not convinced its this simple. These latest mods should have considerably more acceleration and if anything, it has decreased. There was an RXT with me today running 8180 in the same air, which is higher RPMs than its run before.

    What does the ECU do with less that 89 octane gas?

  5. #5
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    8180 is on the rev limiter on a RXT for 06 and up i believe I know it is for the 07 cause i am on it hard with my ET wheel and 15/20r

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    REID2168's Avatar
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    Quote Originally Posted by Jarrett View Post
    Where can I find this?

    I'm not convinced its this simple. These latest mods should have considerably more acceleration and if anything, it has decreased. There was an RXT with me today running 8180 in the same air, which is higher RPMs than its run before.

    your also ASSUMING like most do that your slip is still CORRECT on your stock supercharger and making FULL BOOST like NEW after however many hours are on your boat NOW ........i BET whatever amount u like its below 10 ft lb regardless of the hours on your boat which isnt enough IMO to make FULL BOOST............then u need an AF meter to get the fuel right because first off X skis in general i found to be lean from the factory and now u have added a 4" intake MORE AIR and now a throttle body mod MORE AIR and removed the restrictor in the air intake MORE AIR to what i know is a LEAN SYSTEM to begin with so u tell me what MAY be happening.........LEAN.........u ask for the simplest solutions to what u want.......your NOT gonna get what u want Jarret which is FOOL PROOF GO FAST WTHOUT MONITORING ANYTHING .............get some tools check some pieces and im sure it WILL ROCK until then your in the wind my friend as is anyone that thinks GO FAST is ALL BOLT ON AND GO.............. thats FANTASY LAND.............GOOD LUCK!!!!!!!!!!!

  7. #7
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by Jarrett View Post
    Where can I find this?

    I'm not convinced its this simple. These latest mods should have considerably more acceleration and if anything, it has decreased. There was an RXT with me today running 8180 in the same air, which is higher RPMs than its run before.

    What does the ECU do with less that 89 octane gas?
    http://wahiduddin.net/calc/calc_hp_dp.htm

  8. #8
    Jarrett's Avatar
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    Quote Originally Posted by skoepp View Post
    Thanks skoepp

    Reid, I'm not sure what you were saying there. The SC has 21 hours on it. So adding the latest mods made it leaner, so its going slower at the same RPM?

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    REID2168's Avatar
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    Quote Originally Posted by Jarrett View Post
    Thanks skoepp

    Reid, I'm not sure what you were saying there. The SC has 21 hours on it. So adding the latest mods made it leaner, so its going slower at the same RPM?

    my friend most chargers break in after 3 to 4 hours use and need reset no questions aksed if your looking for TOP PERFORMANCE.........no matter whos it is....will they perform for most people just riding around .....yes... were talking about obtaining MAX performace now though right..............it needs checked and im sure reset and at a minimum of 14+ ft lbs slip moment to produce optimum MAX boost consistenly.......i have my X charger at 16 ft lbs slip moment and it performs and the boost gauge never sways and holds when at rpm........as well yes im saying after what u have done to your boat with AIR MODS i would bet again your boat is LEAN........will this in combination without MAX charger slip and HIGH HUMIDITY change results from day to day and ROB RPM's.........abosolutely...........the charger needs set i assure u and u need a fuel regualtor and AF metering for best fueling and MAX RPM's to get the MAX results from any mods...........BET!!!!!!!!!!!!!!!!

  10. #10
    Jarrett's Avatar
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    Here's what it spit out, what calculation should I be tracking? I'm guessing that Altimeter setting in Barometric pressure?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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