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  1. #1
    TheEngineer's Avatar
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    How much extra fuel from stock injectors?

    IJSBA stock class rules require using stock injectors. If I'm bumping, for example, the stock tune map up 5-10% can the stock injectors keep up? Is there a way to know if the injectors are not keeping up? How does the pressure regulator come into play? I can increase the amount of fuel being used through both the ECU and the pressure regulator?


  2. #2
    The stock injectors are maxed out and tuning gets very sketchy at high power (anything over 260HP)

    Andy

  3. #3
    Boost addict hotbird's Avatar
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    Your probably going to have to find speed somewhere other than the motor.

    Hull mods. Rideplate maybe. Ect...

    Lots of little tweeks can add up. Might try the new lucky13 pump cone also.

  4. #4
    imp0ster's Avatar
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    concentrate on the bottom of the hull. It's free and there's good speed to be gained. Remove all overhanging goo. level the grate with the ride plate, modify the ride plate, fill in the bolt holes everywhere, sand the back 1/3 of the hull from front to back as well as the tunnel. Remove weight where it's not needed.

  5. #5
    TheEngineer's Avatar
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    Quote Originally Posted by whittlebeast View Post
    The stock injectors are maxed out and tuning gets very sketchy at high power (anything over 260HP)

    Andy
    So what is the solution for anyone riding a P-X in the stock class? Somehow these guys are getting their AFR's dialed in. If I run a map tuned for 5% additional fuel will the injectors be able to keep up? Is there a negative consequence to attempting this?

  6. #6
    Pick a spot you want the AFR to be close. Say 8600 RPM. Crank on the fuel pressure till the AFR is close at that RPM and hope the pump does not puke it's guts out at that pressure. Now you accept that you have no control of the injectors anywhere near this RPM and the motor will only get leaner as the RPM goes up. As RPM comes down at some point the injector will go under about 88% duty cycle and you at least can then use the VTech to tune in the hole shot and midrange to get the throttle response reasonable.

    Keep plenty of stock fuel pumps in the tool box at these pressures and have data logging of fuel pressure on the ski so you can catch when the pump starts to let go.

    The rule is stupid and really should be changed, but I don't write the rules.

    Andy

  7. #7
    Moderator beerdart's Avatar
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    Ive been running 82psi @ 8000 RPMs stock fuel pump for four years.

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  9. #8
    TheEngineer's Avatar
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    Quote Originally Posted by beerdart View Post
    Ive been running 82psi @ 8000 RPMs stock fuel pump for four years.
    Wowzsers, why so high?

  10. #9
    Moderator beerdart's Avatar
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    Thats where its happy with AFR..
    Quote Originally Posted by TheEngineer View Post
    Quote Originally Posted by beerdart View Post
    Ive been running 82psi @ 8000 RPMs stock fuel pump for four years.
    Wowzsers, why so high?

  11. #10
    TheEngineer's Avatar
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    Quote Originally Posted by whittlebeast View Post

    The rule is stupid and really should be changed, but I don't write the rules.
    lol, I think the whole stock class thing is a joke. Skis running 9000 RPM are clearly not stock. I hate that I had to mod my boat just to have a chance in CC racing.

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