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  1. #1

    impeller problem? 2012 rxpx

    I recently upgraded my 2012 rxpx with everything in my signature. However, I'm running into speed issues.

    The first impeller I tested was a 15/19r. Using that impeller with mods listed, I was constantly hitting the limiter(Vtech 8375) and only seeing top speeds of 72mph. I figured I needed a different prop, so I went with a 15/21. Now, I am getting around 72mph and max 8100rpm. Using the 15/19, I immediately would hit the limiter and didn't want to run my RPMs constantly that high.

    What's with the secret sauce? Do I need 15/20r? I called Riva and they gave me some BS answer about how the impeller recommendation on their website is based upon ownership of an Athena ECU.

    Solas recommends the 15/21 for a unmodified engine so that's why I went that direction.

    Keep in mind, I'm in TX so I don't know if the extreme temperatures are causing my mph to go down.

    Today I'm going to test the Vtech 102 AGR to see if that helps over the 201 NOR.


    What is everyone is getting speedwise in TX with 2012 RXPX w/vetch?
    Last edited by CronusTX; 08-07-2013 at 10:00 PM.


  2. #2
    stuckmoto's Avatar
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    My guess is Jonatan has a "soft" limiter set on that tune. Have you tried to bump up the limit in the mapedit function? I ran a 8500 tune before I installed springs/retainers, just watched rpms very carefully.
    I know he has been swamped lately and response time has suffered.

  3. #3

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    my 15/20r was repitched by speedfreeks to a 12.5/19. on my rxp-x, last sunday morning i saw 74.5 at 8280-8300, half tank of fuel, 60 degrees, 100% humidity . . . mods include 4" intake, vtech 8375 201 normal and 2009 x intercooler.

  4. #4
    Well 15/19 was hitting limiter 8375 no problem so I don't know how it could be a limiter issue.

  5. #5
    RIVA CREW's Avatar
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    Quote Originally Posted by CronusTX View Post
    I recently upgraded my 2012 rxpx with everything in my signature. However, I'm running into speed issues.

    What's with the secret sauce? Do I need 15/20r? I called Riva and they gave me some BS answer about how the impeller recommendation on their website is based upon ownership of an Athena ECU.
    I'm sorry you feel like we fed you a line of bull, but it is the truth. We spent endless hours testing and tweaking props in order to come up with one that best optimizes performance with "RIVA Stage Kits", which are based around the maps in our Athena ECU. Vtech's maps do differ from ours as your testing showed so it should be expected that the pump impeller would need to be different. It could be a matter of slightly tweaking ours or swapping it out for a different pitch altogether.

  6. #6
    Don't get me wrong, I love RIVA and the support but I think folks are mislead on the impeller.

  7. #7
    Today I saw same issues with RPM. 8100 RPM Max using 102 AGR. 90 degree water temps tho 72mph MAX. I am thinking of getting secret sauce of which is 15/20R.

  8. #8
    JT jpt7779's Avatar
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    Cronus, HE'LL YES the weather we have is killing performance.

    Use this calculator for horsepower and Density Altitude. Plug in your MSL altitude(600' Ft Worth), temp 104, dew point 62, pressure (29.74 today). The result is a whopping Relative Air Density (RAD) of almost 4000', and only 94% horsepower. Add high water temp, and you have a recipe for very crappy performance!

    Bottom line you should be down 250-300 rpm, compared to a nice cool day.

    http://wahiduddin.net/calc/calc_hp_dp.htm

    Great day for performance is: low air temp, low humidity, low dew point, and high pressure over 30.00. This creates lower RAD near your actual altitude. Just play with the inputs you will see the effect.

  9. #9
    Thanks for your input jpt. I'm pretty new to the mod disease and started in mid Summer in TX. Just trying to determine if getting 15/20 would help here.

    It will be interesting to see how quick mine gets when temps are down.

  10. #10
    JT jpt7779's Avatar
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    Quote Originally Posted by RobKman View Post
    my 15/20r was repitched by speedfreeks to a 12.5/19. on my rxp-x, last sunday morning i saw 74.5 at 8280-8300, half tank of fuel, 60 degrees, 100% humidity . . . mods include 4" intake, vtech 8375 201 normal and 2009 x intercooler.
    Here is your secret sauce, SFR pitched to 12.5/19......mine is the same, old 2008 SOLAS SRX 15/20 with Erik's setback mod and repitched to 12.5/19. Since you have a 2012 your Solas should be a SRZ which is already setback, just get Erik to do his magic!

    http://speedfreeksracing.com/home

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