Carb help with dyno information
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Carb help with dyno information

  1. #1
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    Default Carb help with dyno information

    Pump gas 622 dyno run, using a 1250 Dominator, Profiler intake, we ended up with a 107 jet squared with power valves to get enough fuel in the motor. We tried a 1050 Dominator done by Pro Systems, no power valve, annualr boosters, 91 jets, and it ran actually with a better fuel curve, but made a tad less HP. Why such a big jet in te 1250, suggestions to bring the fuel in line. We dropped high speed air bleed from .035 to .028 and it helped, but still required the 107 jet. I want to run a power valve in the boat, and already own the 1250.
    Ignore that bottom pic, that was a dyno sheet for my turbo motor and it has attached itself to this and I can't get it erased,WTH!
    Click image for larger version. 

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    Last edited by Jspeeddemon; 03-17-2013 at 07:45 PM.

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    i have found on alot of my stuff by going to a bigger cfm carb the jets need to be bigger because the air speed slows down pulling less fuel

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    Do annualr boosters help?

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  6. #4
    gn7
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    Quote Originally Posted by Jspeeddemon View Post
    Do annualr boosters help?
    Nothing unusal here. If fact it is very common. The pressure drop thru the carb with an engine that size is not sufficient to move enough fuel thru the jets at part throttle unless they are huge. The huge jets mess with the fuel curve because the jets are only correctly sized when the engine is at the top of it RPM band. A good carb guy might be able to fix the fuel curve with air bleeds.
    1250 isn't really that big for an engine that size, but the throttle plate to venturi ratio makes the tuning of the carb much more critical than a 1150 or even a 1050. No matter who builds the 1250, a 1150 or even a 1050 may prove to be quicker than the 1250. I am not a fan of the 1250 Dom, and not a fan of the 1000cfm 4150.

    If you do not have annular boosters, yes they will help. If you do not have annular boosters, you probably don't have 3 circuit carb with an intermediate circuit either, and that can help the 1250 way more than it helps a 1050.
    I bet the 1050 Pro Systems was a 3 circuit 1050.

    My gut says an 1150 Ultra HP with annulars OUT OF THE BOX will equal the 1250 on top, and almost equal the drivablity of the 1050.
    You don't race dynos. Making more power doesn't necessarily mean good drivability, or acceleration. You have to look at the power across a RPM range of both carbs. More power, but generated over a 300 RPM band sucks if the 1050 makes less power, but over a 2500 RPM range.



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    Here is a pic of the dyno sheet with the Pro System 1050
    From the pull right before it was down across the board less than 10HP all the way, however I wouldn't sacrafice driveability over 5 or 10Hp. It is a performance lake boat after all, just looking to make the best compromise.

    Click image for larger version. 

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    Last edited by Jspeeddemon; 03-19-2013 at 06:38 AM.

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