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  1. #1
    Mothman's Avatar
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    What ring to drop rpm?

    I ran her at 690ft at Benbrook lake this weekend, well for 30min or so. You guys near sea level are so damn lucky. It's a totally different machine down there. At sea level it must be absolutely radical.
    Anyway, after warming up, I cruised up to 70 (on dash) and tried a wot pull, and it hit the limiter, hard. Thought I was trimmed wrong, tried again. Limiter. Tried again thinking a small wake got me. Limiter again and again. I finally eased into it and it spun my 15/25r easily to 8640 (8800vtech) with 1/3 to 1/4 throttle left, so I backed out of it. I couldn't believe it. No gps numbers, sorry.
    I'm running the stock 83 nozzle and need a smaller ring to hold it back. What do you guys recommend? I'll order the riva kit, but the smallest in the kit is an 81. Should I order an 80 also? I have no idea. Oh, I have twin prd's so I'm not worried about stuffing.
    Thanks!


  2. #2
    boost junkie skidoochris's Avatar
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    sounds like you have a cavitation problem
    15/25 seems way to big for a et145
    690ft should not much of a change from sea level

    just raise the limit to 9000+...lol
    Last edited by skidoochris; 09-22-2014 at 09:27 PM.

  3. #3
    Bob 1tommygunner1927's Avatar
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    In my testing, each ring size is worth 60-80 rpm with the Riva Pro (adjustable) Nozzle. Your results may vary.

  4. #4
    dnielsen's Avatar
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    Keep the 83'and repitch the prop.

  5. #5
    Mothman's Avatar
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    I live and usually ride at 3000ft. Up here it's tickling 8600 on a nice flat run, so I know it's not cavitation. It's brutally fast up here, and was waaaay more than I expected way down at 690ft. I knew it would gain power, but good golly, it was a handful. lol
    I was told 15/25r is past the efficiency of the root 15/22r used to pitch up. Slow91 pitched it for me, and I'll try more if it'll yield results, but the trailing edge is pretty durn close to the vanes as is, and I don't want to run into spacing/shimming issues.
    I'll try the riva rings first. Can't hurt to have more parts to line the shelves, right?

  6. #6
    Bob 1tommygunner1927's Avatar
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    You could open up an 83mm nozzle to 87mm and use a Lucky 13 tailcone/spacers.

  7. #7
    Mothman's Avatar
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    I do have both of those parts sitting on a shelf. I didn't have the time to swap them this weekend or I'd of given it a go. I'm a little hesitant though, because the spacer rings on the cone can move a slight amount, and the sharp edge protruding will cause some serious turbulence. I will try 'em, don't worry. The last time I rode at that low of elevation was the day I bought it. The first half hour was spent toodling around Benbrook, giving her a nice gentle heat cycle. lol
    I've ridden at 1000ft on last years build, but that's it. I'll let y'all know if I find a magic setting for 700ish ft, then I'll set my sights on a lake as close to sea level as possible.

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