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  1. #1

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    Riva stage 3 with rude results

    Finally got some good runs in on my Riva stage III RXP with rude s/c and Rude camshaft. With the 14/19 3 blade and the 81mm ring I am hitting the rev limiter at 3/4 throttle and only seeing 77 mph. I also seem to only see about 11.5 lbs of boost so I may have a boost leak to find also. AFR is right around 12 - 12.5( hard to get a good number bouncing off the limiter) Should I use a smaller ring, pitch the prop or both? If Riva claims 80+ at 8400 with the 14/19 3 blade does it seem right that I am only seeing 77 at 8600 rpm? What am I missing here?


  2. #2
    Hydrotoys's Avatar
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    Sorry,
    don't have a good answer for you, but I bet the fast RXP guys will know when they get back from the lake today.

    You know,
    Riva "claims" a bunch, in a perfect world.

    Personally, I'd say you have a freaking monster on your hands, and need to get those RPM's down before you know anything. Too early to worry about what "riva said."

  3. #3
    Moderator The Bandit's Avatar
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    What you are missing is about 2 to 3 mm of pitch on the trailing edge of the prop.

  4. #4
    Im a Rude guy
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    14/19 3 blade? thats stage 2 prop,or not?

  5. #5

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    My mistake. It is a 15/19 skat 3 blade, the riva stage 3 prop.

  6. #6
    rxpdoo's Avatar
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    14-19

    your 14-19 might not necessarly be a 14-19 it could be smaller and that is why you see the higher rpms and the low 77 mph. remeasure the prop. check your pump to make sure it is in good condition and that the prop does not have excess clearance, which could also scrub speed. boost is annother issue, depending on what gauge you use and where it is mounted. you get the most accurate reading installing the boost fitting right after the sc exit. boost drops as it gets closer to the intake manifold. 81 mm is as low as you want to go or you will loose acceleration. unless you don't mind seeing 81-82 maybe at the end of the lake if there is room left.

  7. #7

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    Second mistake - It is currently the 82mm ring. Anyone know what the 15/19 should measure on the trailing edges?

  8. #8
    Quote Originally Posted by bankyf View Post
    Finally got some good runs in on my Riva stage III RXP with rude s/c and Rude camshaft. With the 14/19 3 blade and the 81mm ring I am hitting the rev limiter at 3/4 throttle and only seeing 77 mph. I also seem to only see about 11.5 lbs of boost so I may have a boost leak to find also. AFR is right around 12 - 12.5( hard to get a good number bouncing off the limiter) Should I use a smaller ring, pitch the prop or both? If Riva claims 80+ at 8400 with the 14/19 3 blade does it seem right that I am only seeing 77 at 8600 rpm? What am I missing here?
    If you don't have a SS wear ring and a solid front motor mount you need to do that ASAP. You could have ate a wear ring real quick turning those kinda R's with that much HP.

    You also need to post information...temperature, humidity, water temperature, elevation, etc. I know Virginia gets VERY hot and humid this time of year. That could be part your problem, but then again you are turning a lot of R's. 8600 is also a lot of R's to have a boost leak. A boost leak will kill R's and performance. How was the hole shot?

  9. #9
    rxpdoo's Avatar
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    15-19

    mrracing has the specs sent him a pm.

  10. #10

    Join Date
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    I have a ss wear ring and piranaha front mount. Water and air were both mid 80's. Very low humidity for this area, around 30%. Elevation is sea level. I know a boost leak seems unlikely, but my gauge has been dead on with all my other sc's and I expected closer to 13psi at 8600 rpm. Maybe bouncing on the limiter is effecting the boost.

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