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  1. #1

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    My Riva 15/20R / RR ECU Results

    This is very strange. I am running a Riva stage 1 without the wedge and a RR ECU, hd clutch, RR Intercooler and PPG powerpipe. I regularly run 75 mph at 8450 rpm with this setup. This week I purchased the Riva 15/20R from Richard and installed it. Went out today in a different body of water than I normally ride in. Could not get over 71mph at 7750 rpm. Ran home and changed back to the 14/19r stage 1 impeller and went back to the river (less than 1 hour later, I can now r/r the pump and change out the impeller in under 20 minute) and ran 8350 rpm at 74 mph. Not sure why I was down 100 rpm/ 1 mph. It was a cooler day and I had less fuel than normal, but it was a different body of water. My GPR was normally a little faster at this place. The point is, why did I drop 600 RPM and 3mph with the new prop. It is the riva r series that is supposed to be checked on a pitch block before it ships. Maybe the rr ecu likes the steeper pitch???? I should have swapped ECU's first, but my time today was limited. Can anybody shed some light on this? I should probably send the 14/20 out and have it checked.


  2. #2

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    the 15/20 wont work with the r/r ecu, the power range is differnt and
    your max fuel curve is at a higer rpm,than with the stock ecu.
    THe r/r ecu dosnt make enough power at lower rpm to get the 15/20 up to speeds(when using the rr ecu most people are runing props at 14/18
    to 14/18.5.

  3. #3
    Site Admin Green Hulk's Avatar
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    Damn, i was just fixing to test one of those props. I guess I won't need to go thru the trouble now.

  4. #4
    way2fast's Avatar
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    Riva recommends that the 15/20R be run with their Stage 2 Kit. Any variation from the parts included in the Kit might result in performance that is less than expected.....that is what I was told.

    Richard

  5. #5

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    Richard,
    I am not blaming you in any way and I am still very happy with my purchases from you. I completely understand that everything I am trying is experimental.
    Hulk,
    Please try this for yourself. If you need the impeller I will send it to you. I want someone to backup my results. Maybe your head and cam work will make the difference.

    I am very dissapointed in the ecu if what we are being told is true. Why did we spend $1500 for an ecu that makes less horsepower on the top end? I am a little upset about the fact that a $250 impeller would have accomplished the same thing in the end as a $1500 ecu. The ecu is not a mechanical part like a head or cam that must sacrifice power in one range to make more in another. It can and should be tuned for max power throughout the entire rpm range.

  6. #6
    Site Admin Green Hulk's Avatar
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    Bankyf, thanks for the offer. Nils Castillo has already sent me one of his to try out. I'll give it a shot and post results.

  7. #7
    GRF + DashPac:) seadoo02xp's Avatar
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    it doesnt make less power, it just wants to rev higher, it makes a ton more bottom end and mid power from stock and the reason it revs out higher is so we can run lower pitched props and get some nasty holeshot and retain 75mph top speeds

  8. #8

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    Seadoo02xp,
    I appreciate your input, but it just does not make sense. It needs horsepower and/or torque to rev higher. Why would they intentionally program the ecu to not "rev higher" with a 15/20 prop. WOT fuel and timing curves are what we are dealing with here. Either they are programmed to make max horsepower or they are not. If they are not it may not turn the 15/20 prop, if they are it will. Evidently the stock program makes more horsepower at WOT with my mods because it will turn it(or at least according to Riva and a few people on this board). I might believe that this ecu is optimized to the ported head and rr cam and most of us are just using it incorrectly, but hulks testing will confirm that.

  9. #9
    GRF + DashPac:) seadoo02xp's Avatar
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    i wonder if the vortech impeller would help you in your situation, it puts out more boost especially if you have the ic, it brings your boost back up to where it should be, with the ic it looses some boost with the stock impeller, maybe it is too rich, i just cant see the racing ecu putting out less power, i notice a huge difference when running mine

  10. #10
    Moderator Franko's Avatar
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    Quote Originally Posted by bankyf
    It needs horsepower and/or torque to rev higher.
    Banky, I would have thought so too. But Riva's dyno charts show that the stage II makes more HP and torque at 8100 RPM than it does at higher RPM. I guess there is a point of diminishing returns.

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