Wooooooooo DAWGY!!!!!!

[TexasTimbers]

For those of you who have been "....meaning to get around to it....." when it comes to opening up your muffler, all I can say is push it up high on the priority list.

I have had my muffler off (Hilda the 372) a couple of times and didn't go through with it because I would get side-tracked or just plain hesitant that I was going to screw it up and I would get online and read another article about it but not actually do it.

Well yesterday I did and man-o-man the place where I read somewhere that you gain about 10% power can't be right. It's awesome 8).

I' not sure I needed to even get the 395 this 372 is a scorcher!.

I laid the 20" bar into a walnut yesterday that took the whole blade and she didn't bog down even a little, so I put all my weight into it and she just slowed a little . I even TRIED to get the chain to stop but I was through the cut before I could make it happen.

I think of all the times when I was cutting hardwood wondering if I should stop and talke the time to make this modification - all I can say is I WISH I HAD DONE IT SOONER!

Geez. I can't imagine what Helga (the 395) will be like when she gets her new muffler. Dangerous thats what. I think if you could keep a blade sharp you could cut a battleship in half with her.

just be fore-warned, the first time you fire off your new machine after the mod, and it IS a new machine, be prepared to get goose bumps. It won't sound like the same animal.

Wooooooooooo DAWGY!  8) 8) 8)

[Steven A.]

Can someone tell me about this modification? I have a Stihl 025 I'd be willing to try that on.

Steve

[Ed]

Yup, it makes a world of difference. My 046 has a factory dual port muffler on it. One heck of an improvment.
Now you just need to get the saw ported.  :D

Ed

[TexasTimbers]

Can someone tell me about this modification? I have a Stihl 025 I'd be willing to try that on.

Steve

Go to the Search function and click the Check All box and it will uncheck all the boxes, then check the Chainsaw box, then type in "Muffler Mods". You will find alot of stuff to read and be sure to dig out those embedded links like to Madsens and arboristsite.com etc.

Oh heck never mind I did it for you 

Click Here

[sawguy21]

Be sure to wear ear protection. That puppy will bark like a big dog. ;D

[Ga_Boy]

I opened up my 361, that beast screams...... 8) 8) 8) 8)

[leweee]

kevjay Welcome to the world of modded saws. 8)  Its a good idea to tach the saw & make sure you arn't too lean. Hard to believe that all that power was hiding behind that "anal retentive" muffler. Ads new meaning to the expression " LOUD & PROUD" 8)


PS Keep your eyes open for those" EPA chainsaw cops"... they will be gunnen for you and that "Bad Boy Saw" :D :D :D

[Al_Smith]

 Just a little heads up about tweeking a muffler.If you allow more air to flow,what is exactly what a muffler mod is,you need more fuel in the mix.If you don't set your high speed jet richer,beyond the shadow of a reasonable doubt,the thing will lean sieze on you.

My suggestion is to do a little reading,this site as well as many others that deal with saws has many threads on the subject.I would also recommend you take it a little at a time,bigger is not always better.

A muffler mod will get the most gains on the engine,the cheapest.

 

[TexasTimbers]

Good advice. I had already decided I am not going to use it anymore until I dig up that Madsens article I printed off in the last century on how to tune one after a muffler mod. I went looking for the site just now and it is gone. Finding the article is gonna be a chore.

I'm going to go through the archives here first and then arboristsite and see what I caan find.

The tach I have only goes to 9999 I noticed earlier today. I could have swore the info claimed it would read up to 17500 or something like that. Now I have to order a new tach. Any suggestions. Okay, I'll search the archives for that too.

[TexasTimbers]

I can't find my printed copy of the Madsens guide to tune the saw by ear. Anyone have it on disk perchance and could re-post it? I didn't find it in the archives other than links and they are of course dead.

I want to use the saw today but I don't have a tach that will go that high yet, and I need to set the carb so that it isn't too lean.

I have read extensively the archives this morning and learned alot, but it made for more questions too. I know I shouldn't be running 50:1 but don't know whether 32:1 is too drastic either. I am thinking I should stay with 40:1

Also I meant to find out how I can tell whether the saw has a rev limiter or not but could not find that either.


Edit: If date of purchase (don't know date of manufacture right now) matters as to how you can tell whether it has a limiter or not, I bought the saw in April of last year from Bailey's.

[lmbeachy]

I went home after reading about this and cut a small hole in the muffler on my Sthil 390, it is hard to believe the difference it makes. I did turn the mixture up some, also had to open the idle jet a little to make so it would idle. I have a 066 Magnum, has anybody tried a mod on them, or should you just leave them alone. Lester

[TexasTimbers]

I can only go on what it sounds like here . . .  it sounds like you " . . . went home and cut a small hole in your muffler . . . " now I know you didn't fail to remove the muffler etc.?  ???

You don't want metal chips getting into your cylinder. That spells THE END.  If you simply drilled a hole then take the muffler off, remove the spark plug, get the shop vac, suck the heck out of your cylinder AND your spark plug hole even though they are right there pretty close together and going into the same place, and hope like heck no permanent damage is already done. Suck the muffler too. De-burr everything you drilled/grinded/cut. Heat can cause thin metal edges to come off and blow-back into the cylinder.

Better yet, take her down to parade rest if you know how or take it to your small engine dude and fess up. better to eat a little humble pie than eat an expensive saw like that.
Now I KNOW you didn't do that but I am just saying these mistakes are not hard to overlook in one's excitment to gain more HP  . . . . 

You also want to make sure your hole equals 80 - 85% of your actual EXHAUST port from everything I have read. I stand to be corrected (which hapens often :) Measure the port in cu inches or mm or whatever you want and multiply times .8 or .85 and that shole be the new opening size.

Anyway, apart from all that it is fairly shocking the difference ain't it!?  8)


Edit: changed bad info from intake to exhaust.

[Corley5]

http://www.madsens1.com/ 

[TexasTimbers]

yep i found that page already. The site is closed down though and you cannot access anything from it except the history and the stuff you see there. I had already called the number on the page and talked to Ed. He said he doesn't think they have a copy and the guy that ran the site is gone.  :

What to do. I decided to hang rafters today. in a 35 mph gusts, R-E-A-L C-O-L-D wind.  :-\

I am frozen and can hardly type. Back to the balancing beams  . . . . . . . .

[SwampDonkey]

PS Keep your eyes open for those" EPA chainsaw cops"... they will be gunnen for you and that "Bad Boy Saw" :D :D :D

Yup, included in that are DNR, WCB and if on crown lands, the company inspectors as well.

[TexasTimbers]

I won't tempt fate by saying it can't happen but, it ain't likelyt to happen anywhere i will be. Unless they are watching the forum and decide to teach me a lesson
Even then, they gotta follow me into the bush.  I love the EPA. they are great people   :D

[lmbeachy]

Yep, I pulled the muffler before drilling a small hole and then grinding out a little larger opening on the final outlet. Also, deburred all new cuts, and cleaned muffler before reinstalling it.

[Cut4fun]

Now you really want to get the potential out of a stock 372. Send it to Big Dave Nieger in MI. I have a 357 and a 7900 he has had his hands in modding and they make them seem like night and day compared to stock. The 372 stock, Oh hummm, but with a woods port job them suckers fly.

[woodhick]

imbeachey, what size hole did you put in your 390.  I have one and would like to make this mod but not sure what size hole?  Also did you just drill and ream hole or did you weld any type of pipe into it as I have seen others do?   Can you really tell the difference in the saw.   Thanks. ???

[lmbeachy]

I pulled the muffler and drilled a 5/16 hole in the front part of the muffler. bypassing the baffles. The when I put the spark arrester screen on and was going to replace the front cover I realized that the opening on the front cover was still the same size. I then used my Belsaw sharpener to grind out the outlet on the front cover. I cleaned out the muffler good and deburred all the cut edges. Did I see a difference, man you won't believe it until you try it.

[parrisw]

I have a modded 288xp(walkerized), the muffler is also modded, and I have a stock 394xp, and the sound is way different, the 288 barks way more then my 394, I love the sound of it.  I really want to do it to my 394 too.  ;D

[TexasTimbers]

I want to do it to my 395 too, but I never seem to get past my 372. It handles everything I run across.  8)

Of course once I get to slabbing I will be glad I did.

[parrisw]

Yes, true, honestly, I ve only used my 394 twice since I got it, just for kicks.  My Walkerized 288xp is a BRUTE running a 28" bar, it rips through anything with ease. 

[parrisw]

So if I m reading this right, you want your exhause opening 80-85% of the intake port, does that include the orignal exhaust port plus your new port?? or your new port is 80-85% of the intake port.

Thanks

[TexasTimbers]

parrisw,

I had a brain fart in the post where I said that. It is not 85% of the intake port but the exhaust port. I will modify that after this post. And since posting that and having done even more research I have read elswhere where 85% is a number, unofficilaly tossed out by manufacturers to keep the general DIYer from blowing up his saw.
I don't know who tossed it out there orginally but someone did and it doesn't matter. Some guys think 100 - 110% is best.
Keep in mind, when you measure your modified opening you have to take into account the factory openings which, unless you close them will be part of the equation. You also have to consider the mesh guage on the spark arrestor you install. It can "close" your new opening so to speak to the tune of 50%! Alot has to be considered.
I just got a new muffler I bought off ebay for my 372 because I was not happy with the way I did my mod aesthetically.
Plus I had talked to Don Walker after I did my mod and came away with some info that made me want to redo it.
My advice is not to do it until you are sure you have gathered all the info and then take a crack at it. But whatever you do, make sure you do it!  8)

[parrisw]

Ok, so the total exhaust outlet area has to be 85% of the exhaust port?? 

Thanks

[StuBC]

Anyone want to post a photo of what you are doing?  Sounds interesting, it would be cool to visualize.

[parrisw]

Here is one thats been done, I want mine to come out like this.

[TexasTimbers]

I "opened up" my muffler and then realized I hadn't considered the factory outlets in my computations, so I took a broken recip blade and clamped it in there to partially restrict the flow. Real hi-tech engineering. Now you see why I cautioned you to get all the facts and to figure all your openings and the %mesh restriction you'll get for the spark arrestor.
I did it on my way out into the field and did it in a hurry. Don't do that and save yourself from re-doing it.  :
It looked okay until I stuck the sawzall blade inb there. I would have probably been okay to leave it wide open but didn't want to blow my favorite saw up so went with the safer-than-sorry philosophy.

[parrisw]

I agree don't rush on stuff like that, the one that I posted I think the stock outlet has been blocked off, and then the two front ports added, looks pretty cool though.

[TexasTimbers]

that's the way i am going to do mine too parrisw. I saw a pic last year similiar to the one you posted that was da bomb. The new muffler is waiting for the unibit . . . . . . . . 8)

[woodmakr]

Hey all,

You can still get to the old Madsens site by using the WayBackMachine.  Try this link: http://www.archive.org/index.php then type in www.madsens1.com and have fun.

[leweee]

woodmakr.....thanks for that link. 8)

Carb Ajustment Link

[parrisw]

Just bought a ported 394 muffler of Ebay, like the one in the pic I posted, should have it tomorrow.  Cant wait to try it out, will report back.

[parrisw]

Ok, these numbers just don't add up, with just the two front ports on the modded muffler, the area of the outlets is way more then 85% of the exhaust port area.  Maybe I m doing this wrong. 

Each port on the muffler is 13/16 ID, plus it has the stock port which the baffle has been remove and the port opened up.  Im thinking of  closing off the stock port leaving just the two front ports. 

The exhaust port on the cylinder measures 1 3/8 x 5/8"  its been a while since I ve done any math.  The way this muffler is modded is the way I ve seen many others done.  And I m a little baffled at this.  What am I doing wrong.

[TexasTimbers]

wow. woodmakr that site is cool thanx.

[jokers]

Ok, these numbers just don't add up, with just the two front ports on the modded muffler, the area of the outlets is way more then 85% of the exhaust port area.  Maybe I m doing this wrong. 

Each port on the muffler is 13/16 ID, plus it has the stock port which the baffle has been remove and the port opened up.  Im thinking of  closing off the stock port leaving just the two front ports. 

The exhaust port on the cylinder measures 1 3/8 x 5/8"  its been a while since I ve done any math.  The way this muffler is modded is the way I ve seen many others done.  And I m a little baffled at this.  What am I doing wrong.

Maybe I can help. Let`s start with the area of each port and since you stated 13/16 ID I will assume circular ports.

To determine the area of a circle the formula is π(← that is supposed to be pi but php doesn`t play nice)r² so your equation would look like this, 3.14(13/32 x 13/32) because 13/32 is one half the diameter(the radius) of 13/16. To convert 13/32 to a number friendlier to use, divide 13 by 32 which results in .40625. I`m going to round this number to .406, so then,

3.14(.406 x .406)
3.14(.164836) which equals
.51758504 which I will round to .518 so then,
.518 x 2(two ports) = 1.036(round to 1.04) square inches of open port area. If you screened this port with mesh you would have to use the appropriate open area factor for your size screen to determine your final open area. Hint: You can make a port which is too big, smaller.

Now let`s address the cylinder`s exhaust port area which is 1 3/8 x 5/8. We can divide 3 by 8 so we get 1.375 and 5 by 8 which equals .625 so the area calc for this port is 1.375 x .625 resulting an open area of .859375 square inches which I`ll round to .859 in². So to determine the percentage of muffler port to cylinder port area we will divide 1.04 by .859 which equals 1.21 or 121% open area. Way too big for any saw near stock. You need to perform more detailed calculations using port/time areas, compression, bmeps, etc. to dial in any more precisely than the 85% guideline which works quite well with most saws stock or mildly ported. Usually though, ports larger than 85% just means louder not more powerful.

Does this help?

BTW, somebody check my math!  ;D  ;)

[parrisw]

"jokers"  Thanks that does help, yes I was doing the area of a circle wrong.  And Ya I thought that the modded muffler had too much area by just looking at it.  Im going to close off the stock port on it, and just leave the the two front ports.

Thanks again.

[parrisw]

Ok, I went through this again, and it doesn't make any sense, if I go by the formula 85% of the port area then that means the stock port is too large???

Stock ex port area is .86 sq inches

stock muffler port measures out at .82 sq inches

That means 85% of the port area you should have a muffler opening of .73sq inches, smaller than the stock muffler opening.  Just doesnt make any sense, after hearing all these people of modding their muffler????????????  What

Just had a thought, I guess since the stock port has a screen, that makes it smaller.  But that would still mean, that if you do any muffler mod, the muffler port area will still be too large?????????

[jokers]

Ok, I went through this again, and it doesn't make any sense, if I go by the formula 85% of the port area then that means the stock port is too large???

I wouldn`t say that and I am assuming that we are talking about your 394 which isn`t the latest emissions choked version of that powerhead so it is very likely that your muffler is not unduly restrictive.

Stock ex port area is .86 sq inches

stock muffler port measures out at .82 sq inches

That means 85% of the port area you should have a muffler opening of .73sq inches, smaller than the stock muffler opening.  Just doesnt make any sense, after hearing all these people of modding their muffler????????????  What

Just had a thought, I guess since the stock port has a screen, that makes it smaller.  But that would still mean, that if you do any muffler mod, the muffler port area will still be too large?????????

My calculations show your stock measured muffler port to be nominally 95% of of the cylinder exhaust port. Adding a screen can easily reduce the open area by 10% and this is why so many guys have removed those screens over the years.

BTW, 85% is a pretty good thumb rule but hardly cast in stone. I even referred to it as the 85% guideline because that is how I see it. One reason that the Uni Bit method is so handy, it`s easy to start on the small side and then work your way up incrementally.

[Al_Smith]

Here is a point of view or opinion on the suject of muffler modifications.

Often times people expect the saw rpm s to automatically jump a couple of thousand rpm s .This is not neccessarily true.Rpms out of the wood just make noise,it's the cut speed in the wood that counts.

The whole idea behind reworking a muffler is to allow more fuel,in a usable mixture   to be used within the engine for power.If bigger were better,just remove the muffler but trust me it won't run as good,been there and done that.

Little stub pipes and megaphones look kind of cool and add to a certain amount of austetics but do little if anything for the overall performance.

Because I have so many saws ,covering the whole ranges of sizes ,I tend to be rather conservative on saw modifications.A modest gain of 10 to 15 percent in my way of thinking would be just about right for an everyday usefull saw.

The actual outlet size for the muffler has long been a debated issue on many internet forums .Just remember it does little good to just make the things run louder and blow fuel out the muffler with little gains.My suggestion is to do a little bit at a time and stop when you are comfortable with it.

[jokers]

Here is a point of view or opinion on the suject of muffler modifications.

Often times people expect the saw rpm s to automatically jump a couple of thousand rpm s .This is not neccessarily true.Rpms out of the wood just make noise,it's the cut speed in the wood that counts.

The whole idea behind reworking a muffler is to allow more fuel,in a usable mixture   to be used within the engine for power.If bigger were better,just remove the muffler but trust me it won't run as good,been there and done that.

Little stub pipes and megaphones look kind of cool and add to a certain amount of austetics but do little if anything for the overall performance.

Because I have so many saws ,covering the whole ranges of sizes ,I tend to be rather conservative on saw modifications.A modest gain of 10 to 15 percent in my way of thinking would be just about right for an everyday usefull saw.

The actual outlet size for the muffler has long been a debated issue on many internet forums .Just remember it does little good to just make the things run louder and blow fuel out the muffler with little gains.My suggestion is to do a little bit at a time and stop when you are comfortable with it.

Excellent post Al!

[parrisw]

Ok, thanks again guys, maybe I jumped the gunn a little on putting this muffler on, I will close off the stock port on this modded muffler and se what happens.  Im thinking that the stock muffler with baffle removed would be about right.  But this one sure sounds cool.

Thanks again

Will

[jokers]

Hi Will,

Since you already have the muffler modified, why not experiment a bit with it? Run it as is and time a few cuts and then block the factory opening with something, maybe some wadded up aluminum foil and then time a few more cuts. It wouldn`t need to be an air tight seal, just enough restriction to let you know whether or not you need to mess with closing the stock port. You can also close the stock port by varying degrees by squashing the deflector down.

[parrisw]

Yes good plan, I figured since the two front ports are already too big, I figured closing the stock opening and leaving the two front ones would be better?? 

Thanks again for all your guys help.  I still haven't cut with it yet with the mofifed muffler on it.

[TexasTimbers]

Will, how bout an update. What was the final disposition on the 394?