Double barrel shotgun muffler mod

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steve,
looks are nice but what really counts is what it did to the proformance. by looking at your avtar it appears you know something about gaining BHP in every corner you can. if you want the most out of your saw you can really get into some tinkering.
in the chainsaw world you don't need a dyno to see what you have gained. a simple 8x8 square cant will suit you just fine. start with the stock saw, make three cuts and record the times. make a small change where you think it will help you, make three cuts and record those times. don't make drastic changes all at once because you won't know where you lost or gained anything. one small change at a time. sounds like it may be time consuming but at could become and addition.
i am curious what paul's saw times at stock and what it is running now.
any chance you have any records?
marty
 
BadA** set of pipes! Screens look like they'll be hard to do. When a muffler mod is done, how do you determine how big of an opening to use? Also, do you close off the stock opening?
 
Marty. This 7900 has now been treated to a woods port job and it is no longer possible to use this saw to test the gains of the muffler.....BUT...... I do have another brand new stock 7900 we could test it on. Also get good data on the port job vs. stock with and without the mufflerl mod. Are you busy next weekend? I could bring the saws over for a quick test.
 
testing two seperate saws doen't really prove anything. i have had similar saws be as much as two seconds off in one cut.
the control is testing the same saw after each mod.
i have gone as far as testing a slight change in spark plug gap. marty
 
chainsawworld said:
steve,
looks are nice but what really counts is what it did to the proformance. by looking at your avtar it appears you know something about gaining BHP in every corner you can. if you want the most out of your saw you can really get into some tinkering.
in the chainsaw world you don't need a dyno to see what you have gained. a simple 8x8 square cant will suit you just fine. start with the stock saw, make three cuts and record the times. make a small change where you think it will help you, make three cuts and record those times. don't make drastic changes all at once because you won't know where you lost or gained anything. one small change at a time. sounds like it may be time consuming but at could become and addition.
i am curious what paul's saw times at stock and what it is running now.
any chance you have any records?
marty
Click to expand...

I used the two cut and timed method. I have picked up 1.3 seconds so far. Now I don't know if it it the tunable length or the diameter that has made the gain.

Basically I started out with two 3/8 x 3" pipe nipples. It cut off the first threaded end to get welded. I drilled the two 15/32 hole in the case of the muffler and made my cuts(an improvement, but not as much). Then added one pipe at 2" length and made another cut. I added the 2nd pipe the same length. And made the more cuts. I have left the one threaded end on the pipe so I could use reducers and bells to make a "tunable muffler" as I read in the thread earlier. I got the best time with one of the pipe drilled to a 7/16" ID. I then added a couple "restrictor" bushings to the end off one of the pipes, but lost time, so I tried drilling the 2nd pipe, but didn't gain anymore. So right now I think I'm maxed out wi this sized pipe, but after drilling the 2nd tube and not making anymore gains, I think I have optimised the muffler mod.

Steve

So to answer your question, yes I made some times and did a little investigation, but in all seriousness it is a performer even though it looks are questionable.
 
Marty, We could time the stock 7900 then take the muffler off the ported one and use it on the stock one, the only change to the stock saw would then be the muffler. Would this not measure any gain the muffler would provide?
 
Here is a pic of the first double barrel mod I did before finding this thread.
I made one like others I have seen with the hole in the muffler bracket with a screen on it, but didn't like the way it burned the bark on bigger stuff. This was my big saw not too long ago, and it had a 28" bar on it for a alot of big stuff. This was my answer to direct the gases away a little more. I still haven't got the 55 back. Hopefully this week sometime. I have been on the road for work a lot lately.


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Mike Maas said:
Why don't you guys have sights on the end of your barrel?
Also, why an over-and-under and not a side-by-side?
Click to expand...


sights lol.

The side by side would be hard to achieve with the small constraits of the plastic surounding it. And adding them to the front would be the same as a oval hole that most huskies have. I spent a great deal of time making that setup fit just perfect, at the right angle, etc. It took me a lot longer than the others I have done due to the space I had to work with.
 
Freakingstang said:
sights lol.

The side by side would be hard to achieve with the small constraits of the plastic surounding it. And adding them to the front would be the same as a oval hole that most huskies have. I spent a great deal of time making that setup fit just perfect, at the right angle, etc. It took me a lot longer than the others I have done due to the space I had to work with.
Click to expand...

I think it looks good. Do you notice any change (increase) in power with the double barrel muffler mod vs the previous mount bracket mod?
 
Here's a picture of the pipes that Paul built for me. I think I will put them on my 088.
Paul is obviously a good welder and machinist, not to mention his fantastic ribs.
John

pipes.jpg
 
Gypo Logger said:
Here's a picture of the pipes that Paul built for me. I think I will put them on my 088.
Paul is obviously a good welder and machinist, not to mention his fantastic ribs.
John

pipes.jpg
Click to expand...
Because he can stick two pipes together and cut them off in a band-saw? Yes, brilliant machinist. LMAO.
 
Good point Simon, but Paul was just welding two pipes together and cutting them off with a bandsaw. He wasn't trying to build the space shuttle.:)
John
 

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