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  1. #1
    5Bulldogs's Avatar
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    03 gtx sc rpm - speed - problems

    I have a 03 gtx sc. Last week I was running it completly stock with a R&D intake grate. It was running at 7660 rpms and hitting 63-64 mph.

    I installed a rxp ecu and a rxp fuel regulator and now it is running 7160 rpms and 58-59 mph. It will hit 7400 or so if it comes unhooked.

    Any help ?


  2. #2
    jpeconsult's Avatar
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    Your stock impeller was setup for the 7600 ECU. Since you increased the RPMs, you will need tweek the impeller, OR upgrade the driveshaft, impeller and wear ring. Imagine driving a car and flooring the excellerator and the transmission sating in 2nd gear. The engine is trying to go fast, but the gear will not allow it. The same with the engine and impeller. The impeller is preventing that ski from excelling. Maybe some other members have some input.

  3. #3
    Kaybat's Avatar
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    i think you might have to change the flywheel gear.....watch the rpm's when you do get it right....those things have cast pistons.....

  4. #4
    5Bulldogs's Avatar
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    Quote Originally Posted by jpeconsult View Post
    Your stock impeller was setup for the 7600 ECU. Since you increased the RPMs, you will need tweek the impeller, OR upgrade the driveshaft, impeller and wear ring. Imagine driving a car and flooring the excellerator and the transmission sating in 2nd gear. The engine is trying to go fast, but the gear will not allow it. The same with the engine and impeller. The impeller is preventing that ski from excelling. Maybe some other members have some input.
    I haven't increased rpms I have lost rpms.

    But shouldn't the impeller allow it at least run as fast as with the stock ecu and fuel regulator?

  5. #5
    5Bulldogs's Avatar
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  6. #6
    jpeconsult's Avatar
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    I understand you lost RPMs. I was saying you increased RPMs, since you added the 8100 ECU.

    To get your impeller to spins corrently at 8100, as I appreciate it, you would need to bend it 9mm...1 mm per 100 RPM. That is a lot.

    What does your ski do as you accelerate up to 7600 RPMs? To me, you should remain consistent as your previous ECU, until after you pass 7600, then you should start cavitaing. The 58 lb fpr is supposed to be added, along with the knock sensor harness. Did you add the knock sensor harness, or did you not need to add it?

    I think there is more to it than just adding the ECU (and 58 fpr).

    Read my signature. In red is my next mods (waiting on the workbench waiting for install) based on my research on this forum.

  7. #7
    5Bulldogs's Avatar
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    Quote Originally Posted by jpeconsult View Post
    I understand you lost RPMs. I was saying you increased RPMs, since you added the 8100 ECU.

    What does your ski do as you accelerate up to 7600 RPMs? To me, you should remain consistent as your previous ECU, until after you pass 7600, then you should start cavitaing.
    It accelerates great up to 7160 then it stops pulling. And the rpm stays at 7160 rpm.

    I just installed a new wear ring and impeller and have a aluminum pump. - zero cavitation.

    I have not installed the piggyback knock sensor. Another member said if the ski starts the harness is not needed. I am willing to try the knock sensor, can I just plug it in or does it have to go to the dealer?

    Mike

  8. #8
    It just plugs into your exsiting harness

  9. #9
    Gotta love this sport! 05Limited's Avatar
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    Mike... you should definitely install the knock harness. It may not be your only issue, but it's a logical step in diagnosing the problem.

    Let us know what you find,

    Jeff

  10. #10
    King_Of_Fun's Avatar
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    Doesn't the ECU need to be reprogrammed to match the throttle body? Or did you get a TB that goes with the ECU?... Ron

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