Stihl MS361 upgrades and options

windthrown

Accoring to Lakeside Andy, the stock 361 spark screen is so much larger than that small exit hole that it will not make any difference. Also for any west coast loggers, do NOT remove your spark screens! Fire control is a huge issue here in the western states, and any fires started by logging operations will get you in deep doo doo in a hury. Any problems that they find around a fire is also an issue, regardless of actual cause. For that reason I leave all my screens in, and I mod saws with spark screens left in place. If you design them right and use low smoke oil, the screens have little if any impact.

The way to do screens is to have a larger area of screen than exit area. Or have a large enough exit area that the reduction from the screen results in what you want. Basically you are going to at least double the exhaust area with any of the 361 muffler mods. I forget the exact formula, but there is a ratio of exhaust port to muffler opening area that does not get you any better performance in stock or light port work saws. Generally you want to keep the muffler exhaust opening between 65-75% of the inside area of the exaust port on the cylinder wall side. Any more than that and you are not apt to get any more gains in power, but you will get more noise.

bipot

I have completed modding one of the 361's and reset the H/L settings just this morning. Used the Husqevarna deflection cover and screen with a centered 3/4" square hole in the side of the muffler. Works great. The rpm at nearly wot is about 13800-14000 rpm with idle about 2800 rpm. Cut 4 cookies with the 361 this morning and it was amazing. It still seems a little rich and is using fuel at a faster rate too. I probably need to play with it some more but the temperature and humidity here in Houston was so high this morning that I probably do not have a good setting, even with the tach. I am not yet comfortable with setting the H at wot with the 4 stroke sound and cleaning up with the cut. I am totally deaf in my right ear and about half deaf in the left from an earlier bout with a virus. So, I may need to find someone familiar with this to do that for me or just use the tach. Now, I need to get the other 361 modified and add dual dogs on that one. Thanks for everyones help so far. Have to sign off and talk to my son in England.
Bye

SawTroll

I believe your memory is slightly off - as I remember it (yes, I do) he was talking about the "cage" inside the muffler, not the spark screen!

windthrown

I am certain he was referring to the spark screen area to exit hole area (the sparc screen area is huge compared to the small exhaust hole in the 361). He specifically refers to the screen being large compared to the tiny exit hole on one thread on AS (I can still read threads there, I just cannot post or give rep). I would quote it here, but that would probably rattle one or the other of the forum owners. I will PM it to you...

SawTroll

Yes, thanks for the PM!
The large size of the screen, and the distance from the outlet itself, obviously helps - but it won't totally eliminate the problem with clogging spark screens.

I was referring to a different statement of his, that was about the "cage".

Willard Holmen

Here is a little story from the early 1980s. I was at work falling timber and the Stihl rep comes up to me and hands me a brand new 038 Magnum demo to try out. The saw had the first dual exhaust outlet muffler for this saw. I noticed right away the rewind side chain brake lever support was melting from the new outlet. He sheepisly said he didn't notice it.
By the end of the day the support was almost completely melted off.
On seeing the rep after I said to him..."Back to the drawing board!"
Willard

rbtree

At least with my woods ported 192T, that's not true. With that saw, we greatly enlarge the inner port, which is then covered with the stock deflector---stock but ground back and bent to allow at least double the flow. The total gain in power (measured via cut speeds) is about 25-30%, versus 15-18% with just a ported muffler. However, that deflector easily falls off as it tends to lose its one holding screw--(needs to be tack welded on) When that occurs, the resultant port size is much larger. The saw gets way too loud, BUT the cut speed still increases significantly. The ratio, at this point is probably above 1-1.

I also believe your numbers are off, though I'm rusty. The ratio of the port opening at the muffler interface to the final exhaust should be below 1, but relative to the opening at the cylinder wall, that ratio is typically 1.25 to 1.50.

I do know that some of the saws that Ed Heard did for me have a ratio of well over 1.5... are way too loud, but are fast, and work well and reliably.

__________________
http://www.??????.com/photos/rbtree

williams.j

Does anyone have a pic of the husky deflector added to the muffler?

windthrown

Someone posted several photos of the deflectors on mufflers previously on this thread.

windthrown

These ratios are rough rules of thumb that I got form several builders I know here in the west. Your numbers may well be the case. Difinitive data on muffler port size seems to be nebulous at best. Most port guys do not post much in the way of ratio and porting details. Also they are hard to measure for area as the exhaust ports are ovals and the muffler holes are highly varied, especially when using spark screens.

With the saws that I have ported effectively the muffler openings seem to have biggest gains when they are smaller rather than larger. You get significant gains up to a point, and then they fall off. On my 026, 044, 361 and 310/290 muffler mods, the carb H side metering seems to be the main limiting factor. They also get a lot louder, and they dump more raw fuel out the exhaust. It also depends on your use; I only do working man's port mods. I do not build them to race or for extreme building. I also have spark screens on all my saws, and I am wanting to keep them less loud for use in towns. Piped saws are completely different as well, as the muffler opening has little to do with back pressure waves. I was tempted to buy a 361 pipe from a guy on AS a while back... LOUD? What was that? You say the saw is LOUD?

SawTroll

I once learned about the "spagetti rule", meaning that you should fill the exit from the cylinder with spagetti, and remove 20% to determine the desired muffler outlet with the remaining 80%.....

windthrown

That sounds like a reasonable way to get the right ratio without doing any math other than cutting 20% of the spaghetti noodle.

I wonder if the saw exhaust smells like pasta after that mod?

SawTroll

I have no idea how well it works - the only modded muffler I have (except for removing a few spark screens) is the one Andy made for my 361, and I never measued any outlet.

bipot

Here are a few pictures of the two ms361's using the husky deflector and one with the dual dogs and 25" bar. Great addition for the longer bar, helps keeping it above the ground when sitting at rest.

Attached Thumbnails

         

SawTroll

Yes, a 24" bar is way too heavy for a proper balance with that light powerhead!

bipot

Found that out after the purchase of the 24" bar (you are correct here too). I don't think you could keep the nose of the bar out of the ground without the added chain catcher. I have not found that the longer bar is difficult to use however. Works great for ripping longer logs to be turned.

Cut4fun

They removed and did away with all of my past pics when they did away with photo bucket here. So they left a lot of blanks in threads where I was trying to help you guys out, now you got blanks like they was trying to prevent .

Bipot post some new pics of the husky deflector for you. Stihl MS361 upgrades and options

windthrown

These are the series numbers assigned to saws when they are in development and subsequent production at Stihl. Some series have almost completely interchangable parts, like the 1123 series, whereas some series do not (like the 1128 series, or the new 1140 series). My bet is that the 1142 series will be the 461 and 661, but that is pure conjecture.

1119 038
1120 009, 010, 011, 012
1121 024, 026, MS 260
1122 064, 066, MS 650, MS 660
1123 021, 023, 025, MS 210, MS 250
1124 084, 088, MS 880
1125 034, 036, MS 360
1127 029, 039, MS 290, MS 310, MS 390
1128 044, 046, MS 440, MS 460
1129 020 T, MS 200 T
1130 017, 018, MS 170, MS 180
1132 019 T, MS 191T
1133 MS 270, MS 280
1135 MS 361
1137 MS 192
1138 MS 441
1139 MS 171, MS 181, MS 211
1140 MS 311, MS 362, MS 391
1141 MS 261, MS 271, MS 291

SawTroll

The MS240 (1121), MS340 (1125) and MS341 (1135) is missing from the list!

windthrown

Thanks ST! I will update my list. These saws were not sold here in the US (the earlier 024 and 034 were though).

SawTroll

I know, but not all people on here live in the USA......

The ones I mentioned weren't sold here either, btw - nor did the 440, 640, 650, 290 or the 310 + the 270 was discontinued as soon as the 280 appeared.......

Oooops, the 640 also is missing on your list, as are the 380 and 381.....

...and of course all the older saws.....

You are easily excused though, as I have never seen such a list that is even close to 100% complete!

rick

Windy's numbers are roughly what Brian/Timberwolf came up with in his testing of various outlet sizes.
I think his spreadsheet of outlet size to cut time for a 260 can still be found on AS.

He has said a number of times that while power will continue to increase past 100% of port opening diameter it's a case of diminishing returns, and fuel usage and noise increases exponentially.
Somewhere around 65-85% seems to be a nice compromise on a stock saw.

Box muffler race saw is a different animal again.
He posted a photo once where the exhaust was just a cone the length of the standard muffler.
Awful loud but maximum grunt unless resorting to a tuned pipe.

I think he mostly posts at the Treehouse now but not sure, I seem to be blocked form joining there. Maybe I'm supposed to

windthrown

I am on TH under another name. WT seems to have made too many enemies so his alter egos have to be used on such places. From what I have read, TH posts seem to mostly be limited to about 3 sentences though.

rick

Well take a good long hard look in the mirror young man......

rick

Just haven't seen TW on RS or AS lately, but like everyone else in NA he's probably making hay while the sun literally shines, while we're inside and snuggled up before 5 o'clock these days.
Well, everywhere except coastal Queensland where they think 15*C is bitterly cold, eh Ekka....

SawTroll

I quit posting on TH a long time ago.......

windthrown

What? You are not posting on

The #1 HARDCORE arborist forum, bar, and grill - Enjoy the buffet and libations!

Whatever that has to do with logging, arbor stuff and chainsaws is beyond me.

Welcome to The Mega Ultra Ultimate Hardcore TreeWorld Australian Taco Stand, Gun Shop and Liquer Store!

rick

I hadn't been there for a veeeery long time, but Husq2100 (don't know if Serg is a member here ?) and I were talking on the phone a few weeks back and he mentioned that TW was posting more there than on RS lately so went to have a look and tried to join and was rejected
Didn't look like much happening anyway.

I enjoy Brian's posts, he really does look at things in a logical manner and tries to be as scientific as possible when comparing mods and changes.

windthrown

TW blipped on and off of AS for long periods of time, back in the day. I have never been able to get onto RS. I see many of the some guys on FF and TH and AS. I noticed that Gary has over 20,000 posts on TH now? Talk about dedication. I quit AS at 5,000, and that was insane.

I see that Cutty is trashing talking myself and this site on some other sites too. Amusing. Some people need to get a life. LOL!

SawTroll

TH is playing games with the post count numbers - you never know if they are true or not!