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  1. #1
    Active Member Dray's Avatar
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    Default Exhaust Backpressure

    I am thinking about building a custom exhaust for my 2017 F3L
    and the question of backpressure or lack thereof raised its head.
    I would cut off the oem header pipe about 2" in front of spring
    hooks and run exhaust pipe back to a 2" inlet x 18" long bullet
    style glass pack mounted pretty much where the oem muffler
    was mounted. There would be 45 degree "S" curve in the pipe
    to get it outside of the frame. I would also use the oem muffler
    heat shields on the new muffler. So, would this create enough
    backpressure to keep everything happy? I did a temporary
    mounting of the muffler and this gives me a deeper exhaust
    note that I am happy with.
    Feel free to jump in here with experience/opinions.

    Dray

  2. #2
    Very Active Member BLUEKNIGHT911's Avatar
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    Default BACK PRESSURE

    IMHO , if you guess what your back pressure was ... it's going to be very difficult to get a new one that mimics your Old back pressure. I think you should have your current Back pressure tested ( to verify what it is ) before you proceed. Back in the Day, folks were putting straight exhausts on all types of combustion powered vehicles and would swear it was now Faster than a speeding bullet .... But a dyno test usually proved they actually LOST Power.....good luck with this .... Mike

  3. #3
    Active Member Dray's Avatar
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    Default Exhaust Backpressure

    Hey Mike, My muffler guy says used automotive cats have about 6 ozs.
    of backpressure. Thinks mine should be about 1/2 of that. I do know that
    the cat material in my cat is about 4" or 5" deep and the width of body
    at inlet pipe. I will probably play and see how it works out.
    Thanks for your input!

    Dray

  4. #4
    Very Active Member BLUEKNIGHT911's Avatar
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    Default back-pressure

    Quote Originally Posted by Dray View Post
    Hey Mike, My muffler guy says used automotive cats have about 6 ozs.
    of backpressure. Thinks mine should be about 1/2 of that. I do know that
    the cat material in my cat is about 4" or 5" deep and the width of body
    at inlet pipe. I will probably play and see how it works out.
    Thanks for your input!

    Dray
    Here's the important statement " muffler guy SAYS used auto Cats have ABOUT 6 oz of B-P " ..& .." Thinks yours should be about 1/2 of that " ..... I think SEAT of the Pants testing is going to be a long process..... good luck ....keep us posted ........... Mike

  5. #5
    Active Member Dray's Avatar
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    Default Exhaust Backpressure

    Yep, I think you are probably right. Muffler guy said come by and we would
    do a before and after check for a baseline. I will probably take him up on it.

    Dray

  6. #6
    Very Active Member Wildrice's Avatar
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    Default

    Quote Originally Posted by Dray View Post
    I am thinking about building a custom exhaust for my 2017 F3L
    and the question of backpressure or lack thereof raised its head.
    I would cut off the oem header pipe about 2" in front of spring
    hooks and run exhaust pipe back to a 2" inlet x 18" long bullet
    style glass pack mounted pretty much where the oem muffler
    was mounted. There would be 45 degree "S" curve in the pipe
    to get it outside of the frame. I would also use the oem muffler
    heat shields on the new muffler. So, would this create enough
    backpressure to keep everything happy? I did a temporary
    mounting of the muffler and this gives me a deeper exhaust
    note that I am happy with.
    Feel free to jump in here with experience/opinions.

    Dray

    After I installed the Cat bypass with Big city Thunder I lost some power from a dead stop & couldn't burn rubber anymore--then I found out if I took it up to 10-15 mph I could spin the rear tire. I'd like to tone down the sound a bit--I've considered taking the standard stainless steel baffle that came with the by pass pipe---cutting it in 1/2 installing it along with the Big City Thunder baffle to add a touch of off the line power & tone down the sound level. It won't fit in it's entire length thus the reason for cutting 1/2 off. & installing it at the pipe just prior to the muffler.
    2015 F3's , two 12 volt power outlets Orange & Black

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