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  1. #1
    bscpaint's Avatar
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    what afr is safe for a high boost motor

    I know I saw a table floating around the site once before but now i can't find it, what are safe numbers to run throughout the rpm ranges on a higher 18+ boost motor?

    I'm tired of the guy behind me always saying your ski stinks like raw fuel....


  2. #2
    YAMAHA POWAAAA !!!!! 1_Fast_SHO's Avatar
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    Would like to know as well

  3. #3
    shrabber's Avatar
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    I would say IMO based on my tune there is safe and race tune. So my tune for playing is around 11.5-8 depending on temp. This is a safe AFR for any motor to run with appropriate surroundings. Race conditions would call for leaning it out into the low 12's ( with the risk to the beholder)

  4. #4
    Ale's Avatar
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    you have to remember that afr value you read on your lambda is the average of 4 cilynder.
    we know our sho motor everytime blown pistons n°2.
    so...
    if you read 12... it can be the average of 12 - 13 - 11.5 - 11.5 but not safe.
    so I like run at wot between 11.0 to max 11.5 - 11.8 . it's rich.... but I hope safe enough...
    best option would be.... 4 indipendent lambda sensor .... but never seen on sho platform...

    here a kit from AEM.
    http://www.aemelectronics.com/?q=pro...afr-controller

  5. #5
    shrabber's Avatar
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    Hey Ale how are You thanks for your reply buddy!!! I use a innovate but it's tied into my motec!!! Yes each gauge varies hence 11.5-11.8 is what I consider safe that gives a said gauge a variance to be off . So what ever gauge you have don't go over 11.8 and you should be fine, but having the right calibration for Your afr gauge is mandatory !!!!

    I guess if I must backtrack make sure your gauge is properly calibrated!!!!

    Little confused You said You run between 11.0-11.5 but 11.8 is too rich?? Is that a typo?

  6. #6
    SLAP~YA's Avatar
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    id agree safe is anything in 11's even low 12's in the warmer months.
    i made the mistake of running 12.5 AFR's when the weather got cold they raised to 12.8-13.1 and blew the motor

  7. #7
    shrabber's Avatar
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    Yikes!!! 12 is premium but it comes at cost. If You don't shotgun Your motor WOT All day etc... Like I said earlier the risk is to the beholder.

    In racing it is always about putting Your motor to the edge but that is the gamble/risk You take to go fast.... Risk = Reward at cost.

    With proper Afr's one must also consider proper timming/gearing/ pitch, with all factors being equal

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  9. #8
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    at wide open throttle i set mine up 12.0 On my personal ski's with 21 to 22 psi. of boost at 9000 rpm i have been at 12.1 for 4 years now with no issues at all.

    One thing with boosted motors you do not want to be to lean or to rich, you get to rich with a boosted motor the fuel starts to wash the oil film from the cylinders then you start to scuff up pistons and scoring up cylinders.

  10. #9
    bscpaint's Avatar
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    Ok I'm going to start with 11.5 and go up from there, what about the low and mid range?

  11. #10
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    low i would have at low 13's mid or cruising mid 12's

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