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  1. #131
    ptscon's Avatar
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    Are you sure a buddy didn't prank you and stuck a GPS jamming device on your ski last year?

  2. #132
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by SIECIKSuc View Post
    As I have indicated, Air and Water temps are nearly identical (we are talking a few degrees, ie: 2-3 F warmer running better speed at more consistent RPM)

    ...
    My post was not to resolve every, or even most, points of confusion in this thread. Merely to focus on the direct relationship between RPM and hull speed.

    The hull and the water do not care, at all, about SCOM, engine mods, cold air, etc.

    If the jet pump configuration, impeller and the hull has not changed, then the impeller RPM almost entirely determines the speed the hull will go. More impeller RPM means more speed, less impeller RPM means less speed. And the same impeller RPM should produce the same speed.

    Without the SCOM the engine computer reduces impeller RPM (after a moment of ‘overspeed’) and that RPM determines the (ECU regulated) hull speed. A working SCOM removes the ‘overspeed‘ RPM reduction, so presumably the sustained impeller RPM is somewhat higher and the hull speed correspondingly faster.

    Any changes to engine power, ECU tune, cold air intake, whatever, almost the only way they can affect hull speed is by affecting the sustained impeller RPM at wide open throttle. Again, as long as the hull and the pump/impeller remain the same.

    If after whatever modifications the sustained impeller RPM is higher but hull speed is not (enough), then something has changed to reduce the effectiveness of the impeller at that RPM.

    Wear ring, impeller damage/wear/pitch, jet pump issue, trim nozzle/angle, hull damage, something.

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  4. #133
    Mod less, ride more! troyheb's Avatar
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    Quote Originally Posted by SIECIKSuc View Post
    What info is confusing?
    There have been a few posts that didn't read any of the thread and offered up opinions, but reading start to finish (I know it's long) really keeps the information pretty much exactly in line...
    If you have any parts you are confused by I would be happy to clarify as I can. I just tried to post the cliffnotes to help speed up the "getting up to speed" on the thread.

    I 100% agree with you, I have been trying to work through it and made some mistakes along the way and now I am looking to bring it to a performance shop instead of the dealer.
    Hopefully I will be able to do so this week/weekend.
    I have read enough. The only that is confusing is what mods are on the ski right now.
    Why dont you list everything that is CURRENTLY on the ski.
    I also stand by my statement that you need to bring that ski to someone other than whoever has been working on it. I believe you mentioned something about bringing it to Chris at Eastside. He has a very good reputation.

  5. #134
    Quote Originally Posted by troyheb View Post
    I have read enough. The only that is confusing is what mods are on the ski right now.
    Why dont you list everything that is CURRENTLY on the ski.
    I also stand by my statement that you need to bring that ski to someone other than whoever has been working on it. I believe you mentioned something about bringing it to Chris at Eastside. He has a very good reputation.
    Quote Originally Posted by K447 View Post
    My post was not to resolve every, or even most, points of confusion in this thread. Merely to focus on the direct relationship between RPM and hull speed.

    The hull and the water do not care, at all, about SCOM, engine mods, cold air, etc.

    If the jet pump configuration, impeller and the hull has not changed, then the impeller RPM almost entirely determines the speed the hull will go. More impeller RPM means more speed, less impeller RPM means less speed. And the same impeller RPM should produce the same speed.

    Without the SCOM the engine computer reduces impeller RPM (after a moment of ‘overspeed’) and that RPM determines the (ECU regulated) hull speed. A working SCOM removes the ‘overspeed‘ RPM reduction, so presumably the sustained impeller RPM is somewhat higher and the hull speed correspondingly faster.

    Any changes to engine power, ECU tune, cold air intake, whatever, almost the only way they can affect hull speed is by affecting the sustained impeller RPM at wide open throttle. Again, as long as the hull and the pump/impeller remain the same.

    If after whatever modifications the sustained impeller RPM is higher but hull speed is not (enough), then something has changed to reduce the effectiveness of the impeller at that RPM.

    Wear ring, impeller damage/wear/pitch, jet pump issue, trim nozzle/angle, hull damage, something.

    K447 I appreciate you jumping in with your wealth of knowledge, and will try to reply to what your saying here, in a way that I understand it, and please let me know if I am missing the mark here.

    RPM and Hull Speed are relative, 100% agree.
    More RPM's = Hull Speed faster, I however am down on RPM's and Down on Speed since the work done.
    Impeller hasn't been changed, and as far as I can tell, is not damaged in anyway.
    Hull hasn't been changed. *** except now thinking, the Intake Grate has been replaced under Warranty (Entire plate was replaced and all hardware fittings with the latest recall)
    I do not know if the intake grate is capable of affecting that much of a loss.

    How I understand the overspeed without SCOM...
    When the ski was brand new, it would get to 72mph, and after sustained for a moment, the ECU would realize !!too fast!! and it would drop off RPM's from 8040rpm to 7800's (going off memory) and I would see my sustained speed drop to 68-69 fluttering on the dash.

    I then got the SCOM and ran the same temps/locations/conditions, and got to 77-78 super consistently running the 8040rpm limit solid no flutter no break.

    What I think this tells me, and please correct me where I am wrong, is that the ski was always going to be faster then what it was "speed limited" to, and likely could be much faster still than what the rev limiter would hold it back to be, which is far beyond what the speed limiter would hold it back to. In my specific example, Speed limiter wanted to hold it to 68mph, rev limiter would hold it to 78 at 8040RPM.
    The best I ever saw was 79mph at 8040rpm on the dash. Again that was a STRONG 8040, not a blip under 8k running sustained speeds with runs multiple directions and so on.
    I believe the 2019 RXT-X ski bone stock, in theory is capable of much more than what it's limited to.
    If that same stock ski, had only removed the speed limiter, and moved the rev limiter to say 8500, then the stock engine ski would do somewhere between 8040rpm which it did easily limited, and 8500 rpm.
    I understand that it might not reach the 8500rpm mark at all without mods, but my point is regardless of how high over the 8040 original limit you would going, you would GAIN relative hull speed...
    *** If I am wrong please let me know***

    The problem that I am having is, after all the changes and there was a lot of them done at once, the RPM is lower (thus the top speed is lower) and I can't for the life of me imagine why.
    The list of mods that I laid out, I would assume would if anything give me more RPM and more speed, as well as increase the reliability and stability of the engine/cooling system.
    Then, by going back on just the Tune to where my baseline was, and reintroducing the SCOM I am still lower **consistent** RPM, and considerably lower speed.


    A stage 2 IMUK + 8500 tune should be seeing over 8300rpm's consistently I would expect, based on everyone I have spoken with.
    I am at 7900ish consistently. To me that screams something is wrong.

    When you look at the list of mods would you think that any of them cause loss in RPM?
    I would think maybe the strainer affects waterflow through intercooler a tiny bit?
    Maybe the air intake is less efficient then the comparable Riva one? But would it be that much worse then Stock? to Starve the engine of air?
    I am thinking about doing holes and frogskinz but I also don't want to put a bandaid on a bullet hole here... if something is off I want to fix it before making any more changes.

  6. #135
    Quote Originally Posted by troyheb View Post
    I have read enough. The only that is confusing is what mods are on the ski right now.
    Why dont you list everything that is CURRENTLY on the ski.
    I also stand by my statement that you need to bring that ski to someone other than whoever has been working on it. I believe you mentioned something about bringing it to Chris at Eastside. He has a very good reputation.

    It's not confusing if you read the whole thread like I stated.
    If you don't want to read the whole thread, I understand completely its long, so like I said in the post your replying to... I posted Cliffnotes of everything to make it easier for you/whomever.
    I did do that already, multiple times throughout the thread, including the previously mentioned Cliffnotes provided to you so you don't have to read 12-13 pages of fodder.
    I ALSO stand by your statement, and said so, and am currently working on bringing it to a NEW shop to review and I will keep everyone posted on their findings...
    I don't know Chris or Eastside, but thanks for the recommendation, they will be next on my list to reach out to if the current help can't support it.

  7. #136
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by SIECIKSuc View Post
    ...
    I then got the SCOM and ran the same temps/locations/conditions, and got to 77-78 super consistently running the 8040rpm limit...

    ... if something is off I want to fix it before making any more changes.
    I am not sufficiently knowledgeable to say whether the SCOM or some other factor may have created misleading speed or RPM indications on the factory dash.

    I seem to recall reading in the past that Seadoo has two separate internal GPS speed measuring systems. One for the ECU to use while limiting top speed and a separate, less accurate GPS feed for the speed numbers shown on the dash. I do not know if that is still the case with current models. Nor do I know how/whether SCOM interacts with the dash display.


    It does seem like there is a potential problem with the engine configuration. And that problem (or problems) is reducing the expected power (in terms of maximum sustained RPM). If there is a problem it may or may not have anything to do with the modifications.

    Sometimes things go wrong and are merely coincidental to the changes you have been making. I expect this is part of the reason some others have suggested letting a professional have a look. The experience of having worked on many of these machines (in many tune configurations) can translate into an efficient diagnostic process and, hopefully, prompt resolution of the issue(s).

  8. #137
    moparguy's Avatar
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    Sic, overfill oil will make a massive difference, i experienced similar issue a while back. Have you reset your throttle body?(you can do that with the Maptuner)

  9. #138
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by overboost View Post
    Air temps will rob you of power big time, so make sure when you test that the air temps are same, try it with seat off so it can get lots of fresh cooler ( as cool as possible ) air and see what it does
    The power robbers are humidity, barometric pressure, water temps, and last.....air temps.

  10. #139
    Quote Originally Posted by moparguy View Post
    Sic, overfill oil will make a massive difference, i experienced similar issue a while back. Have you reset your throttle body?(you can do that with the Maptuner)

    Yea, I got that from a few folks and did some research on windage on these ski's... seems like it's a real problem for sure.

    First time I checked it it was a little high and that was cold, and on the ramp, so I was like, eh, it's guna be lower than that so it will be below the mark for sure...
    Checked the catch can and there was like 3 baby drops so I thought I was good...

    Next time I checked it just to be sure was after running the ski for 2-3 mins in the water. Flat on the water, it read over the second bump again.
    I didn't have the time with fathers day to buy a siphon and all that. Also I was planing on bringing it to someone so figured I would let them handle it.

    At this point, I am going to have Erik from SpeedFreeks review the ski completely.
    I've talked to him a few times on the phone and he seems like he really know's his shit, and has the backing from Jesus G whom told me to contact him, as well as others here on the forums that have a ton of experience and for whom I have a good deal of respect for. If these guys say he's a good dude who can help, well that's the plan then.

  11. #140
    Any update on your ski? My 2019 GTX Limited 300 is down 400 rpm and I haven’t been able to figure out why.


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