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338xpt muffler mod

Discussion in 'Chainsaw' started by Spokerider, Jan 22, 2019.

  1. Spokerider

    Spokerider ArboristSite Operative

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    Guys,
    I have a lightly used Husqvarna 338xpt in original condition.
    I am wanting to do a muffler mod to it. No other porting, head or skirt mods planned for right now.

    The plan is to tig in a length of tube into the muffler.

    What I need to know is.......
    What should the ID of the tube be?
    Locate it where on the muffler?
    Point it down at 45 deg? Angle it forward or rear-ward? Or perpendicular to the muffler face?

    Pics of this mod and feedback regarding the effect, positive or otherwise, would be appreciated!

    Thank you.
     
  2. ThackMan

    ThackMan ArboristSite Operative

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  3. Spokerider

    Spokerider ArboristSite Operative

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    Thanks for the pic Thackman.
    Yes that's the concept I was thinking of.
    My 338xpt is a different configuration than your saw however.

    Anyone else?

    Have the total sum surface area of existing exhaust hole and an added hole, to equal roughly 85% the surface area of the cylinder head exhaust port? Sound correct?
     
  4. Shop's Chops

    Shop's Chops New Member

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    I operate, repair, and sell a lot of chainsaws and I've lurked on here for years and I've just modded a 338xpt yesterday after rebuilding the motor and all that jazz. So this was the post that sucked me into joining...

    So, here you go. After I replaced my muffler cover (because when I got the saw it was missing) the new cover came with a hole already in it (must have been a newer version) so at that point I figured why not a dual port. So I drilled a hole fitting a small pipe inside then with the mig welder tacked it into the angle that would line up with the installed cover. Then welded her up, pretty simple really. The old muffler was a little banged up but it should work fine. Tonight I'll see if there is any notable power difference but I'm not holding my breath on that. 20190313_193249.jpg 20190313_192626.jpg
     
  5. Spokerider

    Spokerider ArboristSite Operative

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    Chops,
    Thank you for chiming in, and posting pics of your work.
    It looks great. I guess the hole on the bottom of the muffler cover is a dead give-away, as to where to place the tube. My cover doesn't have that hole, so I will make one.

    Please let me know how the muffler mod adds to performance.
    Will you be re-tuning the carb for the increased flow?

    I haven't done anything to my little 338 xp saw yet, but I have made a scabbard style saw holder for the saw. It's mounted on the swing away tire carrier on my rear truck bumper. Ready for the trail-blocking blow-downs.
     
  6. Shop's Chops

    Shop's Chops New Member

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    Yes I did re-tune the saw so we will see. I'll also be using it on a tree job this weekend for the first real time since the break in and now for the muffler mod too. So fingers crossed it will be worth the effort? :) So far from what I can tell it should be a runner.
     
  7. Shop's Chops

    Shop's Chops New Member

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    So I just ran it through some cured oak and it didnt slow or bog down.

    Now heres the answer to the golden question of if it was worth it or not. Well, if you think the HP gain is gonna be super noticeable I'd say noticeable but not huge. I think its snappier with the throttle and has a little more power but not a whole lot.

    So is it worth it? Well first off it was basically a free mod. I had the pipe laying around and the only investment was time. So for that I'd say yes. We'll see more after I run it in a tree this weekend meaning if the down pipe is gonna burn my leg or some of those unknown factors that might pop up later?

    Well I hope this helps and overall I think the 338xpt seems to be pretty decent. It's easier to work on then some other tophadle saws I've messed with and a runner. Better then anything it's all orange and not one of those creamsicle saws :) just kidding :) I'm not trying to start a make or model fight even if I'm a Husqvarna guy.

    Here's a link of the ol girl running after the mod.

    -Shop

    https://m.facebook.com/story.php?story_fbid=1648035505340388&id=100004018642676
     

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