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  1. #11
    Thanks for the replies.

    I see most people recommend 93 octane with 9:5:1 pistons. I'm in California. The highest we have is 91 Octane. There is a gas station where I ride that has 100 octane. Since I can't get 93, upon starting this rebuild would you use 91, 100 octane or a mix?

    Secondly, if I cannot adjust or view timing with a siemens ECU, which ECU would you recommend with this set up? I need a Riva Racing EVU? I don't think I am buying another ECU. smh.

    I don't have the bigger fuel pump but I have a rrfpr and VT1100s.

  2. #12
    tiderider's Avatar
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    Quote Originally Posted by Smashrockwell View Post
    Thanks for the replies.

    I see most people recommend 93 octane with 9:5:1 pistons. I'm in California. The highest we have is 91 Octane. There is a gas station where I ride that has 100 octane. Since I can't get 93, upon starting this rebuild would you use 91, 100 octane or a mix?

    Secondly, if I cannot adjust or view timing with a siemens ECU, which ECU would you recommend with this set up? I need a Riva Racing EVU? I don't think I am buying another ECU. smh.

    I don't have the bigger fuel pump but I have a rrfpr and VT1100s.
    You can mix 91 with 100 to get a lower Octane mixture. I smell BOOM in the near future...

    Octane Calculator - www.bazellracefuels.com

  3. #13
    Hell naw. Notty boom. This thing will run fine, I hope.

    Does the newer Bocsh ECU allow timing adjustments with a Maptunerx? I can't use a Bosch ECU on my year ski but If I gotta buy a new ECU for timing I'm going to put this motor in a new hull.

  4. #14
    tiderider's Avatar
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    Quote Originally Posted by Smashrockwell View Post
    Hell naw. Notty boom. This thing will run fine, I hope.

    Does the newer Bocsh ECU allow timing adjustments with a Maptunerx? I can't use a Bosch ECU on my year ski but If I gotta buy a new ECU for timing I'm going to put this motor in a new hull.
    Timing is viewable with the Bosch ECU and Maptunerx.

  5. #15
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    Sounds like it's MOTEC time

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  7. #16
    Quote Originally Posted by suck my wake View Post
    I've run 93 with the 9.5-1 pistons with the Riva Racing ECU in my 06 with no issues and that was with the 3 rude charger spinning 8600 rpms but I did have a bigger fuel pump with a return loop system running 65 psi with boosted regulator..... 1 point in compression isn't that huge but it does make it that much more important that you use premium fuel and have a good fuel system. At higher boost or Rpms than that I would recommend 100 octane
    DO you recall how much you had to advance or retard timing with this set up?

  8. #17
    tiderider's Avatar
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    I don't think your set up is anywhere near his with your cam upgrade. This makes it even more difficult to tune with a stock siemens ecu besides the 9.5:1 pistons. Riva Racing ECU contains that information, but no cam was upgraded on his set up, different story.

  9. #18
    You're right. Well I can't see myself buying a Motec or another ecu for a 2003 GTX. Since I have another crankcase, a new set of 125mm 8:4:1 Cp pistons, and my old rods, I think it would be cheaper to run this engine and risk blowing it up than to buy a motec. I could get an entire new engine for less than $2900.

    Let's say I blow this engine up. I'll rebuild it with 8:4:1s, then I can just run a riva tune on my siemens ecu with the maptunerX? In this case timing would not be a big issue because I simply have a stage 4 with a cam. If I go this route, and the engine blows, I'm looking at $400 for a engine bore + replacing whichever components got taken out by the detonation.

    The other option is spending $2900 on a Motec? Hell naw.

    So this is my logic:

    I am going to start the engine running the Riva tune that is closest to my set up. I will use 100 octane. I was considering a data logger but why'd I need that if it won't read, and I cant adjust timing on a siemens ecu? I have an afr gauge that I will watch for fuel and I will let the knock sensor do its job on timing if it detects knock. Seems idiotic but to me a Motec on this hull is more foolish and costly than a complete rebuild.

    Lets say I fire it up, and the timing is way off. What will happen? It will knock and the knock sensor will signal the ecu to retard/advance timing, right? It will retard timing until it doesn't detect knock then it will advance a bit and set timing there, correct? If I run it at low rpm what is the real danger? Will I be able to see knock sensor info with a maptunerX (not unless I get a data logger, smh)?

    And I appreciate the knowledge but I wonder how much of this is just spookism? Who has actually blown up an engine running 9:5:1 pistons on a sea-doo? Specifically because of detonation.

    Since I'm going crash test dummy with it, any recommendation to put me in the safe zone would be appreciated.
    Last edited by Smashrockwell; 07-24-2021 at 02:55 AM.

  10. #19
    tiderider's Avatar
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    Good luck. It won't last long at all..


  11. #20

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    Quote Originally Posted by tiderider View Post
    Good luck. It won't last long at all..
    why don't you answer his questions?

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