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  1. #1
    bttek1's Avatar
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    Problem I am having with RR ECU!!

    Hello everyone.. This is the second time that I have encountered this problem on a customers RXP. I have tried everything to try to remidy this and I am running out of options. Here is the deal:

    I am currently working on a customers RXP that has a Rotax Racing Cam, RR intercooler and RR ECU. Installed is a Solas 14-19 impeller. With the stock ECU, the boat accelerates violently to 8100 RPM no matter how hot the weather is. Current conditions here is Miami are outside air temp at 90 degrees and 89-90 degree water temps.

    The problem is that when I connect the RR ECU, the boat feels lazy and will NOT rev past 7700 RPM's. I have checked everything!! Changed the gas to 93 octane Chevron.. I was using 93 octane Amoco.. A/F ratio is 12.2-12.4 everything else looks perfect. The only thing that I can think of is that with the RR ECU, perhaps the timing is too advanced causing detonation which the knock sensor is picking up??? Has anyone run into this problem before??

    As a test, I immediately put the stock ECU back in and the boat immediately accelerates great and hits 8100 RPM's almost instantly. I put the RR ECU back in and again its lazy and revs up to 7700-7800 RPMS but takes some time to get there...

    Any ideas????


    Brian


  2. #2

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    did you remove the knock sensor? the rr ecu comes with directions
    Also if this was done then I would check with a smaller prop like an 14/18
    this will get into the fule curve and make better power

  3. #3

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    It should blow through the 14/19 prop like butter. The Stock ECM on runs to 8100 or 8200, if its hard 8100 o the limiter. Ive had that problem.
    Put new plugs in it The RR ECM
    Racing cam on mine needs to be retarded slightley.
    Some like it advanced but can never go wrong retarted for RPM, If the cam is off coulple degree they run like crap 500-700RPM off with RR ECM worth checking.

  4. #4
    bttek1's Avatar
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    Thanks for your reply.. This boat does not have the knock sensor update harness that you are referring to.

    Unfortunately, there is no way that I know of to determine whether the problem is being caused by real or fake engine knock.

    The fact that the stock ECU works great and the RR ECU is not performing well points be in the direction of too much timing causing KR.

    I have even tried to disconnect the KS or to "fool" it but I believe that the sensor is looking for a particular frequency and if it does not see this sound, then it puts it into limp mode and flashes the check engine.

    Brian


    Quote Originally Posted by Krazy-K
    did you remove the knock sensor? the rr ecu comes with directions
    Also if this was done then I would check with a smaller prop like an 14/18
    this will get into the fule curve and make better power

  5. #5
    bttek1's Avatar
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    Its definately not a cam issue as the boat accelerates like mad while using the stock ECM. ONLY when I connect the RR ECU does it not perform well and its max RPM is only 77-7800.


    Thanks!!

    Brian

    Quote Originally Posted by Burnwater
    It should blow through the 14/19 prop like butter. The Stock ECM on runs to 8100 or 8200, if its hard 8100 o the limiter. Ive had that problem.
    Put new plugs in it The RR ECM
    Racing cam on mine needs to be retarded slightley.
    Some like it advanced but can never go wrong retarted for RPM, If the cam is off coulple degree they run like crap 500-700RPM off with RR ECM worth checking.

  6. #6
    GRF + DashPac:) seadoo02xp's Avatar
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    what ecu did you buy the stock class or modified, and what year is your boat, if it is an 05 and you bought the modified ecu you need to cut the resistor out of the harness if it is an 04 it just needs to be removed,
    i had the stock class rr ecu and it wouldnt rev either, i installed the modified one and it reved out great

  7. #7
    bttek1's Avatar
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    The boat is a 2004 RXP. The update on the knock sensor was removed. The RR ECU is for modified boats, NOT the stock class RR ECU.

    Does anyone know a way to remove the knock sensor temporarily just for testing without the boat going into limp mode and flashing the check engine??


    Brian


    Quote Originally Posted by seadoo02xp
    what ecu did you buy the stock class or modified, and what year is your boat, if it is an 05 and you bought the modified ecu you need to cut the resistor out of the harness if it is an 04 it just needs to be removed,
    i had the stock class rr ecu and it wouldnt rev either, i installed the modified one and it reved out great

  8. #8
    Jarrett's Avatar
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    Lemme guess, it's a yellow 04 RXP...

    My buddy Franko (and a couple others) have had this exact same problem. Frank has been through everything looking for the issue with no resolution. We have even swapped ECUs and throttle bodies between our skis. Mine works on on my green RXP, but does not work on his yellow RXP.

    Glen Perry and Mark Underwood have both given up on trying to figure this one out by phone. If you find the answer, I am sure Franko would love to hear it. It's got to be an eletrical thing.

  9. #9
    bttek1's Avatar
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    Hello Jarrett... Nope, its not a yellow one.. Black and green.. This problem is really driving me nuts. The boat goes like a bat out of hell with the stock ECU but when I connect the racing ECU, it is awful.

    Like I mentioned, the air/fuel ratio is near perfect so the only other thing I can think of is that with the racing ECU, it is detecting knock and pulling the timing back. This is why I would like to temporarily disconnect the knock sensor to see if this is truly the problem.

    In reality, now that Nills has his awesome fuel controller available, all anyone would need would be to have a stock ECU that is capable of revving to 8500. It seems almost silly for people to go out and spend so much money just so they can get the engine to rev higher!!

    Is anyone else having this problem or know of anyone that has?? Any solutions other than ditching the racing ECU and staying with the stock one??


    TIA!!

    Brian

    Quote Originally Posted by Jarrett
    Lemme guess, it's a yellow 04 RXP...

    My buddy Franko (and a couple others) have had this exact same problem. Frank has been through everything looking for the issue with no resolution. We have even swapped ECUs and throttle bodies between our skis. Mine works on on my green RXP, but does not work on his yellow RXP.

    Glen Perry and Mark Underwood have both given up on trying to figure this one out by phone. If you find the answer, I am sure Franko would love to hear it. It's got to be an eletrical thing.

  10. #10

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    hey whats up your a tech in miami i live in miami ,who are you i know pretty much of all of you guys whats your shops name ?i have pretty much the same set up as you but the cam but i do have pistons a had a problem with mine in the begining but it was the knock sensor update removed it problem gone 8400 rpms 79mph where do you ride ??

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