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  1. #1

    AFR is leaner with larger injectors...Any thoughts????

    Here's the setup on our first three runs:
    04 RXP
    X-Charger
    Riva Air Intake
    Stock injectors
    Stock impeller
    For the above the LM-1 readings on all three runs were very consistent at AFR 12.9 turning 8150rpm.

    Changed the injectors to 42's added pump wedge then made two runs.
    AFR for both runs were 14.0 at 8150.

    The only thing that makes any sense to me is the injectors can not be 42's?

    Any thoughts greatly appreciated.


  2. #2
    speedskixp's Avatar
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    Quote Originally Posted by yacser1 View Post

    The only thing that makes any sense to me is the injectors can not be 42's?

    Any thoughts greatly appreciated.
    They may not be 42s or you have a clogged injector throwing everything off. Pull your spark plugs and see if they all look the same.
    Do you have a pic of the 42s?

  3. #3

    Join Date
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    Quote Originally Posted by yacser1 View Post
    Here's the setup on our first three runs:
    04 RXP
    X-Charger
    Riva Air Intake
    Stock injectors
    Stock impeller
    For the above the LM-1 readings on all three runs were very consistent at AFR 12.9 turning 8150rpm.

    Changed the injectors to 42's added pump wedge then made two runs.
    AFR for both runs were 14.0 at 8150.

    The only thing that makes any sense to me is the injectors can not be 42's?

    Any thoughts greatly appreciated.
    do you have a rrfpr if so what is it set at. if you dont have one you need to get one.

  4. #4
    R88ory RXP's Avatar
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    Quote Originally Posted by yacser1 View Post
    Here's the setup on our first three runs:
    04 RXP
    X-Charger
    Riva Air Intake
    Stock injectors
    Stock impeller
    For the above the LM-1 readings on all three runs were very consistent at AFR 12.9 turning 8150rpm.

    Changed the injectors to 42's added pump wedge then made two runs.
    AFR for both runs were 14.0 at 8150.

    The only thing that makes any sense to me is the injectors can not be 42's?

    Any thoughts greatly appreciated.
    There is a possibilty that with the extra power you would make with additional fuel you were going hard into the limiter, Being in the limiter will make you lean. R88

  5. #5

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    Quote Originally Posted by R88ory RXP View Post
    There is a possibilty that with the extra power you would make with additional fuel you were going hard into the limiter, Being in the limiter will make you lean. R88
    That's exactly what I was thinking. Add 1 mm to the prop and try again. The limiter starts coming in around 8150.

  6. #6
    bigbubba1989's Avatar
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    +1 for the limiter making it lean

  7. #7
    Thanks for the thoughts on the leaning out issue.
    I will post a pic of the injectors.
    I was planning to change the impeller to a 15/20, will do and advise.

    However, I quick question. If I'm banging the rev limiter, shouldn't I see a lean spike on the LM-1 plot indicating lots of air since none was used in combustion. I'm assuming the rev limiter will not allow spark when it triggers. Am I thinking right on this?

    The first 3 passes showed this large AFR spike on the lm-1 plat with the 38's, I didn't think till now this maybe indicating that I'm on the rev limiter.

  8. #8

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    Quote Originally Posted by yacser1 View Post
    ... If I'm banging the rev limiter, shouldn't I see a lean spike on the LM-1 plot indicating lots of air since none was used in combustion. I'm assuming the rev limiter will not allow spark when it triggers. Am I thinking right on this?
    These ECU's start pulling out cylinders periodically starting around 8150 but doesn't pull them all til around 8350. It's truly a "soft" limiter. If it's only pulling every 8th combustion cycle, it will show up as leaner the whole time since the gasses mix in the manifold.

  9. #9
    JD 1's Avatar
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    Quote Originally Posted by engineermike View Post
    These ECU's start pulling out cylinders periodically starting around 8150 but doesn't pull them all til around 8350. It's truly a "soft" limiter. If it's only pulling every 8th combustion cycle, it will show up as leaner the whole time since the gasses mix in the manifold.
    +1

  10. #10
    Thanks to all. Got it +1. Heading to the water the weekend with the bigger wheel. Will advise.
    thanks again

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