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  1. #1

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    High RPM misfire??

    Hyt guys, I am having wjhat seems to be a high RPM misfire above 11 psi, just lloking for some ideas / solution. Here is the deal, I can ride the ski all day at about 11 psi and it seems to be fine, the rpms are 8350. If I try to turn the boost up past 11 psi I get what seems to be a misfire once I full throttle it, the ski wants to buck and surge and the afr's will go from 11.5ish to like 14 then off the gauge rich very quickly. The ski has 200 hours on it, im thinking I may need new coils. also, the tps has been zeroed with my candoo.

    Another bit of useful info is that before I installed the riva ecu the problem was even worse with the stock ecu, I was never able to full throttle it with the turbo and the stock ecu.


  2. #2
    MSRXP's Avatar
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    Fresh plugs, and put a walbro in. Sounds like the oem pump is maxed out.

    Also, has your cam timing been adjusted?

  3. #3
    hero's Avatar
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    try swapping your coilpacks with 1 of your friends ski...had the same problem with 1 of my mates ski as well under 10psi is fine but above 10 starts to miss fire..how many bar of fuel did u have on your ski when it happen??

  4. #4

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    plugs are new, I have a walbro 255 installed. It does it with any amount of fuel.

    As for cam timing, I posted pics of the cam gear installed and everyone here thought it was right, I also came up with the right compression numbers.

  5. #5
    MSRXP's Avatar
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    If that's the case then I would say coil packs as mentioned above. It's either ignition or fuel related. But the fact that your afrs jump, makes it seem like more of a fuel issue than ignition. What injectors are you running? Possibly they are failing at higher pressure.

  6. #6

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    Quote Originally Posted by MSRXP View Post
    If that's the case then I would say coil packs as mentioned above. It's either ignition or fuel related. But the fact that your afrs jump, makes it seem like more of a fuel issue than ignition. What injectors are you running? Possibly they are failing at higher pressure.

    I am running bosch 50# from Jerry. It seems like it misfires a few times then it like looses all power for a split second. Below 11psi I am fine though.

  7. #7
    Got Boost? psycho rxp's Avatar
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    hard on the limiter???

    bosch 50's are alot for the riva ECU to handle. I ran 48# bosch with my old turbo/ Riva ECU, to around 85mph 19psi boost.
    could be too much base pressure, and rising too far...

  8. #8

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    I dont have the reference line hooked up to the regulator, base pressure is around 58 psi. It doesnt sound like the rev limiter, plus tach will say about 8000 when the problem occurs. This is a recurring problem that I have had, now that I think about it, it did this with the xcharger too. I swapped to the turbo and it was really bad until the riva ecu went in, then it was cool to 11 psi.

  9. #9
    MSRXP's Avatar
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    Hook the reference line up so it will rise. It's apparently not getting enough fuel. Even with the ecu and 50's you still need the regulator to be set to rising rate. Not static.

  10. #10

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    Quote Originally Posted by MSRXP View Post
    Hook the reference line up so it will rise. It's apparently not getting enough fuel. Even with the ecu and 50's you still need the regulator to be set to rising rate. Not static.
    The afrs are 11.5 full throttle at 11 psi. I would think if it was leaning up as I turn the boost up I would be able to see it on the wideband.

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