880 muffler mod question

[BobL]

I have a question for all you muffler modders out there. I don't necessarily want to get more power out of the saw jawdrop, what I want to do is redirect the exhaust from an 880. Instead of it coming out on the right hand side (RHS) and forward (towards the log) I would like to get it to just come straight out the RHS.

The reason for this is that during milling the forward directed exhaust reflects off the log and onto the operator who normally stands directly above the line of reflection. Some of the exhaust also bounces back between the operators legs. Here you can see the location of the exhaust port relative to the milling frame. X marks the port opening and the arrow show the direction of the the exhaust.


Here is a close up of the current exhaust port.


I was thinking of removing the current port and replacing it with a plate with a 4" stub pipe like this so the exhaust gets directed entirely down.


Or down and back from the operator like this - I'd curve the pipe rather than use an angle.


What diam/length pipe (ie max-min) would be appropriate?

Anything else I should look out for?
I can weld a bracket onto the ally mill for support if needed.

 

[Lakeside53]

Just guessing.. add about 10-15% more diameter than the current hole to compensate for the pipe length. You could go quite a bit more if you wanted to "open up" the muffler, but you'd need to retune the H screw.

Just take a stab and try it - easy to make a plate/pipe for that muffler so no loss if you chuck it and make another.

 

[serial killer]

I don't see a problem with that. I have used thinwall copper plumbing pipe for muffler mods, and silver soldered them onto the muffler. Make sure the area of the new pipe is at least as big as the area of the current opening.

 

[BobL]

OK - that exactly the sort of info I was looking for - thanks for that - I'll cut out a handfull of plates and bend up some pipes and see what happens.

cheers

 

[BobL]

The existing exhaust exit hole in the plate covering the spark arrestor has a diam of 14 mm or an area of 154 mm^2

There is more than sufficient room on the plate to use a nice chunky 25 mm (OD) diameter ally pipe with 3 mm wall thickness which makes it 19 mm ID and makes it 283 mm^2 or 84% bigger. I would then turn up some 15, 16, 17 and 18 mm ID sleeves to constrict the pipe and start experimenting a bit. eg a 15 mm ID constricting sleeve would be a 15% increase in area.

Sounds like a couple of weekends of solid farting around coming up? Any comments on this approach

 

[Lakeside53]

Good idea.... Remember to richen up the carb if you significantly increase the size of the orrifice. And.. it's likely rev limited by the coil so it gets a little tricky.

They sure get LOUD with bigger outlets!

 

[B_Turner]

Good idea.... Remember to richen up the carb if you significantly increase the size of the orrifice. And.. it's likely rev limited by the coil so it gets a little tricky.

They sure get LOUD with bigger outlets!

I personally would put up with a little exhaust as compared to the volume an 880 is capable of. My 880 already puts out a formidable sound level/quality even with the stock muffler - which is pretty substantial compared to my 3120 muffler.

Specially when milling for hours on end. (insert head ringing graphic here....)

 

[Lakeside53]

I agree... except I hate the exhaust (particularly for the last few cuts when I'm crawling along the ground in 2 feet of saw dust!) as much as the noise.

For milling.... I'd run that pipe to a flex connector that connects to a trailbike muffler mounted on the mill! Hmmm.. just might do that...

 

[B_Turner]

I agree... except I hate the exhaust (particularly for the last few cuts when I'm crawling along the ground in 2 feet of saw dust!) as much as the noise.

For milling.... I'd run that pipe to a flex connector that connects to a trailbike muffler mounted on the mill! Hmmm.. just might do that...

I do know what you mean, esp on a hot windless day.

I wonder how things turned out for that Stu guy in Tokyo that put a muffler on his chainsaw for milling in the city.

 

[brncreeper]

I'll throw mine in too just so you can get more ideas. EHP did the muffler mod and as you can see it's a little bigger than the stock 14mm exit, lolol.

One word of caution: EARPLUGS. I wouldn't want to mill with this saw for very long because of the noise. My 3120 is opened up too, but it's no where near as loud as the 088.
The power goes hand in hand with the noise though, Here's the 088 with a seven pin sprocket and 404 full sequence chain in hickory. The 3120 through the same cant with 3/8 chain didn't even come close.
<embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i38.photobucket.com/player.swf?file=http://vid38.photobucket.com/albums/e134/gschildroth/Midwest%20GTG/EHP088.flv">

 

[BobL]

Thanks for the input guys.

I'll throw mine in too just so you can get more ideas. EHP did the muffler mod and as you can see it's a little bigger than the stock 14mm exit, lolol.

That's why I thought a series of reducing sleeves would be useful - I should hopefully be able to find a balance between power and noise.

I do know what you mean, esp on a hot windless day.
I wonder how things turned out for that Stu guy in Tokyo that put a muffler on his chainsaw for milling in the city.

I know this guy from another forum and have swapped tool making ideas. He's milling away very successfully since he fitted the muffler. His blog is at http://www.ablett.jp/workshop/csm2.htm .
Its fascinating to see what he has done CSMing in the city.

 

[BobL]

880 Muffler mod

Well here it is. The tubing has been bent 3 ways to meet the direction and gap requirements etc

The bits, 1" (25 mm) OD 3/4 (19 mm) ID ally pipe bent 3 ways to meet the direction and gap requirements etc


The rings are explained below.
Original opening on the muffler is 14 mm.
The sleeves have openings of 14, 15, 16, 17 and 18 mm, and then there is no sleeve at all, so the straight thru opening is 19 mm.


The sleeves sit in a recess in the opening and are held in place by a pair of 4mm allen bolts threaded into the base plate and coming thru from the outsider.
The last 5 opening represent increases in areas of 15, 31, 47, 65 and 84% respectively.

I will start with the 15 mm and tune upwards from there - can't fire it up as I'm doing this at home.

Here is what it looks like on the saw.


There is just enough gap between the exhaust and the mill to sneak the chain past so I can still replace the chain while the powerhead is on the mill. The gap between the chain break and exhaust is real tight - it does go on but I have to hit it quite hard. I'm still thinking what to do with it.

The main reason I'm doing this is to redirect the exhaust away from the user in the milling position.

View from the top. Exhaust cannot be lower than mill or else when mill/saw is placed on ground exhaust will take weight.


One more shot - purely just to show off!

 

[tdi-rick]

Nice Bob !

Do you want a copy of the program to design and build a full on pipe now ? :biggrinbounce2::

 

[BobL]

Nice Bob !

Do you want a copy of the program to design and build a full on pipe now ? :biggrinbounce2::

Tempting, very tempting . . . . . . . . . .

 

[polexie]

Very nice piece of work!! Looks like a pimped 880 now with all that bling bling chrome, wanna hear that sucker run.

Thanks,

Lex

 

[046]

nice job!

an easy way to determine volume for odd shaped opening is with my spaghetti method of measurement.

simply take a handful of round spaghetti cut down to 2in length or so.
then stuff into original opening. pack tight as you can get it.

then remove spaghetti and count.

now do the exact same procedure for new exhaust opening.
by comparing number of spaghetti it takes to fill up openings. one can determine fairly close percentage of increase vs original size.

posted detailed instructions with pic's a year or so back.

 

[blsnelling]

Have you been able to do any testing to see which insert you'll stick with ?

 

[BobL]

Have you been able to do any testing to see which insert you'll stick with ?

I have only been able to briefly try the 14 mm insert (I can't test at home - inner city suburban block and all that) which I expected to be the same as the original opening (also 14 mm) or maybe even a little more restrictive as the pipe itself must add some constriction. This proved to be the case with the 4 stroking thing happening at 11,500 rpm

Since then I have replaced the 14 with the 15 mm and will have to wait until the weekend to test that insert and maybe a couple of others.

Sorry I'm a bit slow with all this
a) I'm trying to be careful and
b) SWMBO added significantly to my project list this weekend.

Cheers

 

[redoakneck]

Ever find out what size ring works best??


What is SWMBO?


Thanks again for all your tips!!!!

 

[ptjeep]

Its funny that you replied to this thread today as I have been thinking about it also. I spent the last three afternoons milling some pine with my 394 and the exhaust fumes were terrible, burning my eyes and hard to breathe. I was pushed for time so i dealt with it. Before i mill again i will make a similar type of muff mod, its bound to be much better than the stock outlet.