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  1. #1
    skigolfnut's Avatar
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    Rotax Racing ECU questions

    Does anyone know what happens when you hit the rev limiter on a Rotax Racing ECU?
    does it retard the timing?
    cut fuel?
    both, none?


  2. #2
    jbombino's Avatar
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    Rotax Racing ECU questions

    Quote Originally Posted by skigolfnut View Post
    Does anyone know what happens when you hit the rev limiter on a Rotax Racing ECU?
    does it retard the timing?
    cut fuel?
    both, none?
    RR is very aggressive on timing and tends to run lean no safety features are used like Riva racing ECU does.

  3. #3
    skigolfnut's Avatar
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    so what does it cut back on first when you hit the limiter?
    I was seeing some afr lean spikes when I hit the limiter then it would settle down at 100 rpm under 6550

  4. #4
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Re: Rotax Racing ECU questions

    He is asking how the ecu limits rpms at redline. Does it cut fuel, or spark, or just kick timing back?

    Sean

  5. #5
    skigolfnut's Avatar
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    I finally got a answer,
    "It will start to pull fuel and then at the hard limiter it will kill spark. If you are seeing 8650 on the dash then you are in the pulling fuel range and this will cause it to run lean. 8550-8600 no worries"

  6. #6
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Re: Rotax Racing ECU questions

    So sort of what we thought then.

    Good to have an official answer.

    Sean

  7. #7
    skigolfnut's Avatar
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    exactly,
    I was thinking at 8550 it was starting to pull fuel, because I was starting to see lean AFRS 12.9, but that is not the case,
    I will bring up my base fuel pressure in the RRFPR to see if that cures the lean and try to bring it back to 12.2,
    Then I will put the 84-83 nozzle ring on and tune for 8600 wide open throttle,

  8. #8
    Quote Originally Posted by skigolfnut View Post
    exactly,I was thinking at 8550 it was starting to pull fuel, because I was starting to see lean AFRS 12.9, but that is not the case,
    I will bring up my base fuel pressure in the RRFPR to see if that cures the lean and try to bring it back to 12.2,
    Then I will put the 84-83 nozzle ring on and tune for 8600 wide open throttle,
    Any time the fuel or the ignition or both is pulled, pure air and raw fuel head thru the exhaust. The o2 will always see this as dead lean as the o2 will smell o2 in the exhaust. The problem with cutting fuel is the intake dries out and when the fuel is returned, the ECU needs to add a fair amount of fuel to rewet the intake ports. Cutting spark tends to put raw fuel and it can explode in the exhaust when spark returns. This is fairly hard on a turbo.

    What sort of boost are you running at 12.2 AFR. What sounds a little lean and you may find gains if you go a little fatter. I tend to aim for about 11.0 - 11.5 at15 lbs of boos on most of the stuff I tune.

    Do you have data logs off the bike? I would love to snoop around at them. Racing logs are always best.

    Beast

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  10. #9
    skigolfnut's Avatar
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    no dataloger, and with the ET-137 wheel it is supposed th have 14 lb of boost at 8600 rpm, I am hitting 8550,
    I am going to dial up the rrfpr a little and see if that helps,
    if that doesen't help, I might have to go to bigger injectors,

  11. #10
    Steve-m31164's Avatar
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    Old thread I know ........ are you talking about a 8650 limit ecu or 8800 . The limiters start coming in at about 50-100rpm below limit ? Can anyone tell me the timing curve or max timing on a 8800 08 ecu as im thinking of using one on a turbo ski @ 15-18lb of boost .

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