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  1. #31
    Quote Originally Posted by Hurricane1000 View Post
    Sending you a private message....

    Dave
    Hello! Me too please))

  2. #32

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    Most LSA setting for stock to mild cams like svho or na cams would be to leave the exhaust alone and only move the intake 2 or 4 degrees. This will result in good idle and more bottom end. Always retune after changing LSA. The bigger cams use LSA that move the exhaust. I have a RC-3 cam that runs this way.

  3. #33
    APE has the correct Gears for the 2018 , or you can call Faith @ Webcams and she will help you out.

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  5. #34

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    Quote Originally Posted by onefastgp View Post
    APE Racing makes some adjustable gears also.
    The part number is ACS1800Y -16 for 2018 SVHO

    C J

  6. #35
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    Curious to see what you find when testing different settings. So far I have tested 6° advanced on the intake cam with the exhaust cam stock and only noticed improvement in the bottom end punch. No gain top end. I was told that top end will only be improved by retarding the exhaust cam. Next I tried the intake cam at 4° advanced and the exhaust cam at 2° retarded. Didn't notice much of a change in bottom end or mid range and the top end was unchanged. I may adjust them again next season. I'm looking for more top end, but do not want to run higher than 93 octane fuel.

  7. #36
    pwc4life's Avatar
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    For what it's worth, here is the Riva tuning recommendation sheet for an SHO engine

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  8. #37

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    Did you record the runs and log the data? You have to re tune when you move the LSA. I have run 5 different settings on my Stage 3 ski with a 19 wheel and RC-2 cams. The cam operating range is determined by the lift and duration. This sets the RPM range and max RPM. Tuning the LSA or overlap shifts the power band. The bigger cams run the bigger overlaps. You have to watch cylinder pressure to make sure your not outside your octane level. I do not record static cylinder pressure when I move the LSA because its not that important to me.

    Robert

  9. #38
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    Quote Originally Posted by rcrisafulli View Post
    Did you record the runs and log the data? You have to re tune when you move the LSA. I have run 5 different settings on my Stage 3 ski with a 19 wheel and RC-2 cams. The cam operating range is determined by the lift and duration. This sets the RPM range and max RPM. Tuning the LSA or overlap shifts the power band. The bigger cams run the bigger overlaps. You have to watch cylinder pressure to make sure your not outside your octane level. I do not record static cylinder pressure when I move the LSA because its not that important to me.

    Robert
    Robert, I was running the R&D gears with their R3 tune on my '13 FZ with a 12-14 lb. wheel. Per their instructions a retune was not required. I ran the recommended setting for my setup which was 6° advanced on the intake and stock on the exhaust. Per R&D's instructions I should have gained 150 plus rpm up top and over 1mph top end. I only saw gains in the bottom end. I also find it interesting that Riva's and R&D's recommendations based on their testing are very different. What settings do you recommend if I'm looking to pick up top end power and speed? Thanks.


  10. #39

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    I would say you should try the +5 intake and -2 exhaust setting. It is interesting that you do not have to retune the ski. If you can get more power up top, I would recommend a taller prop to get speed at the same rpm. The motor should have the power there to carry it. If the motor breathes better it could pick up rpm too and you should see a speed increase there also.

    The other thing you do not see published is the actual LSA number like 120 or 108 for the chart above. I have seen some LSA numbers on the R&D instructions for what I assume are stock cams.

    Robert

  11. #40
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    Quote Originally Posted by rcrisafulli View Post
    I would say you should try the +5 intake and -2 exhaust setting. It is interesting that you do not have to retune the ski. If you can get more power up top, I would recommend a taller prop to get speed at the same rpm. The motor should have the power there to carry it. If the motor breathes better it could pick up rpm too and you should see a speed increase there also.

    The other thing you do not see published is the actual LSA number like 120 or 108 for the chart above. I have seen some LSA numbers on the R&D instructions for what I assume are stock cams.

    Robert
    From what I've gathered, LSA is calculated by averaging the lobe center angle of the intake and exhaust cams. Advancing either cam decreases the lobe center angle and retarding either cam increases it. Please correct me if I'm wrong.

    With that in mind, this is where I get curious... I believe you can achieve the same LSA multiple ways. For example, a 117° LSA is produced by advancing the intake cam 6° and leaving the exhaust cam stock, but I believe it can also be achieved by advancing the intake 8° and retarding the exhaust 2°. My question is will they perform differently even though the LSA is the same? If differently, how so?

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