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  1. #1

    19-21 FX HO - Top load intake grate, bolt onís, worth it?

    Hey All,

    So Iíve done some research and have read that installing a too load intake grate on the 19-21 FX HO actually causes a loss of speed?

    The FX SVHO came with a top load intake grate.. But I also know that Yamaha limits the RPMís to keep the speed limited to ~70mph, so with the SVHO, they are not worried about a little loss in top speed/rpm, because they are already maxing out..

    So my question is, is it worth installing a top load intake grate on the 19-21 FX HO? Currently in stock form, I am at ~7200 rpm going ~56-57 mph, according to the built in speedo.

    My Riva Ride plate just came in, so Iíll get that installed this weekend and hopefully get it tested, though the things Iíve read seem to point at it not really making a difference until you get to 70mph, but I guess any gain will be an improvement.

    Iím happy with the ~56-57 MPH, But I will do any bolt onís I can do to achieve more. Not interested in tuning due to cost and extended warranty coverage.

    So the next question is, there are several options for a too load intake grate, the Riva is the one Iíve read about actually loosing mph, but I could get the OE SVHO intake grate, are there any otherís? Will they all slow down the ski?

    I will also be removing the Ribbon.

    Thanks!

    -TheChad


  2. #2
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by TheChad View Post
    Ö I will do any bolt onís I can do to achieve more.
    Not interested in tuning due to cost and extended warranty coverage.

    Ö I will also be removing the Ribbon. Ö
    You do not consider removing the flame arrestor disc inside the intake manifold to create (a perhaps small) warranty risk?

    Built-in speedometer is not accurate, and will become less accurate as you make changes.

    Before you start changing things I will suggest you use a GPS based speedometer app or GPS device to establish the actual maximum speed your FX goes under typical water and air conditions for the area you ride.

    You may also want to add an accurate tachometer to compare with the factory dash tach.

  3. #3
    Quote Originally Posted by K447 View Post
    You do not consider removing the flame arrestor disc inside the intake manifold to create (a perhaps small) warranty risk?
    No, because it is removable and easily reinstalled and there is no way for anyone to know it was ever removed.

    Quote Originally Posted by K477 View Post
    Built-in speedometer is not accurate, and will become less accurate as you make changes.

    Before you start changing things I will suggest you use a GPS based speedometer app or GPS device to establish the actual maximum speed your FX goes under typical water and air conditions for the area you ride.
    You are correct, but for a baseline and comparing, it does not matter.

    It would only matter if A) I actually cared about the accurate actual speed. B) If I was going over 70 where the built-in speedometer no longer reads.

    -TheChad

  4. #4
    WaterDR's Avatar
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    My honest advice is this….stop. You can’t make this machine faster without a tune and prop and what you really need is a super charger. It’s just chasing a dream otherwise.

  5. #5
    Quote Originally Posted by WaterDR View Post
    My honest advice is this….stop. You can’t make this machine faster without a tune and prop and what you really need is a super charger. It’s just chasing a dream otherwise.
    I will agree to disagree.

    Also, as I mentioned, I don’t really care how fast it goes, I don’t care. You can beat me in a straight line? Wooo. Who cares?

    If I get a few hundred RPM’s, I in-fact DID make it go faster, soo there’s that.

    I didn’t buy the ride plate to gain any speed, I bought the ride plate to hopefully make the ride better. Hopefully get it to stop favoring the bow and plowing/spraying water.

    By doing that, it should also gain some speed, if not, again, don’t care. But yay if it does.

    I’m removing the Ribbon, because I can’t see in any way it not restricting airflow, if it gains some RPM’s, yay! If not, again don’t care. But it certainly should make it run better, than it already does!

    Same goes for the intake grate! Don’t really want to loose speed, but if I can make a handling improvement, yay!

    -TheChad
    Last edited by TheChad; 09-03-2021 at 01:11 AM.

  6. #6
    I fitted an Yamaha SVHO intake grate to a stock FXHO and i lost 10 kilometers per hour, the hookup was very good but noticeably slower.

  7. #7
    Quote Originally Posted by Allenor View Post
    I fitted an Yamaha SVHO intake grate to a stock FXHO and i lost 10 kilometers per hour, the hookup was very good but noticeably slower.
    Thank you for that Input. I assume you also lost RPM’s then?

    I do wonder, everyone says you need a tune to run a different impeller, I assume that is because it increases the RPM’s and causes you to bounce off the limiter…. So if one has an HO, which is ~500-600 RPM from the limiter and adds a top load intake grate, which further reduces the RPM’s, if then installing a different impeller would restore the rpm’s, and/or bring them near the rev limiter…

    More research is in order…

    -TheChad

  8. #8

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    I believe the loss of speed with the top load intake grate is due to "stuffing" of the impeller - actually stuffing more water into the impeller than it can push out, which of course adds drag resulting in loss of speed. To counter this, you need to turn the impeller faster or use an impeller that can push more water at the same rpm. It takes more power to do either.
    The top load intake grate should reduce cavitation issues since it allows more water to the impeller at low speeds as well.

  9. #9
    I am a bit confused, you are not worried about speed? Yet everything you want to do is speed related in one form or another.

  10. #10
    Quote Originally Posted by Wild Thing View Post
    I am a bit confused, you are not worried about speed? Yet everything you want to do is speed related in one form or another.
    Yes/No.

    Please read my reply to WaterDR. Any speed gain is a secondary to a handling, ride, etc improvement.

    IE: Ride Plate = Get bow out of the water so itís not running bow down. A secondary effect of this, is that it *should* also gain speed.

    I know the benefits of a too load intake grate, that is why I would like to get one, but I donít really *want* to loose speed either.

    -ThaChad

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