Author Topic: Dual Port Muffler Experiments  (Read 314 times)

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Offline KilliansRedLeo

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Re: Dual Port Muffler Experiments
« Reply #10 on: May 14, 2014, 11:41:40 am »
Right now I am experimenting with a 372XP top exit muffler as my test subject. I am going to try two approaches. First a 0.800 ID pipe done in the usual manner, sticking out the bar side of the muffler. I have done up three of these all with different length pipes. Pipe lengths are 1.5, 1.75 and 2.25 inches. All with the same internal protrusion depth.

It dawned on me that 0.800 ID pipe may be a little large when combined with the factory exit. So, I made up a copper blocking plate that goes where the screen would go. This way I can run the saw with modified mufflers with and without the factory exit being open. I will post some pictures of the mufflers later in the day, so that everyone can inspect. The outlets are thin wall steel pipe.

Next I am going to make up a couple of 'tuned pipe' versions e.g. the stinger on a piped saw. There are plenty of expansion chamber design programs out there but unfortunately there are none for the box style mufflers used on chainsaws. So this will present a lot of messing around. There is a secondary challenge here in that you cannot have 5-7 inches of pipe sticking out the side of a work saw. However looking at the pictures 660 posted, it is possible to hide most of the length inside the muffler just as was done on the 550 pictured. For a tuned pipe to work correctly and deliver results it has to be the only exit on the box. Also if using 0.800 pipe that pipe cannot be within 0.800 from any corner or internal wall of the muffler. The pipe does not have to be straight either, it can be curved like a pretzel if that gets the length you need inside the box. Looking into some flexible steel pipe similar to the jacket on old BX cable to try this with. 
"When the people fear the government...you have tyranny....When the government fears the people....you have liberty"

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Offline aclarke

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Re: Dual Port Muffler Experiments
« Reply #11 on: May 14, 2014, 01:08:29 pm »
Is there much of a scavenging effect on a strait tube or does it need to be tapered? I.e megaphone exhaust

Offline KilliansRedLeo

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Re: Dual Port Muffler Experiments
« Reply #12 on: May 14, 2014, 02:13:10 pm »
Adam, not to my knowledge, IMO the best tuning rpm would be midway between saw's peak torque rpm and peak HP rpm.
approximately 9,000-10,000 would be my guess but we will see.  Saw would be on the pipe as it tries to slow from peak HP to peak torque rpm.  The pipe would not let it do that.

First picture is from the left the factory muffler, next two are 1.75 long pipe and 2.25 inch pipes
Second Picture is the test saw a 365SP with a AM BB kit and OEM Stihl 064 piston, Walbro RWJ-4 carburetor, XT intake setup.
Third is a close up of the 1.25 inch pipe muffler on the test saw
Fourth is all the muffs so far and the saw.

Need to put a bar and chain on the saw and run it to see what is up. All of this is subjective since it is only my opinion and I am the only one running the saw.
 
"When the people fear the government...you have tyranny....When the government fears the people....you have liberty"

Thomas Jefferson
1743-1826

Offline Cut4fun .

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Re: Dual Port Muffler Experiments
« Reply #13 on: May 14, 2014, 02:20:31 pm »
Make sure to check and adjust carb for each muffler.  The piped ones I tested were way different then my CM cover and OEM DP cover tuning.
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Offline KilliansRedLeo

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Re: Dual Port Muffler Experiments
« Reply #14 on: May 14, 2014, 02:29:53 pm »
Without a doubt, but no time today. Actually will have to retune twice for each muffler because I am going to run each one with and without the blocking plate I made to close off the factory outlet. Got to get to paying customers work and quit playing around with my own chit. LOL!
"When the people fear the government...you have tyranny....When the government fears the people....you have liberty"

Thomas Jefferson
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Offline aclarke

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Re: Dual Port Muffler Experiments
« Reply #15 on: May 14, 2014, 04:29:48 pm »
The oem stihl 056 has a long tube inside the muffler and extending out quite a ways. Must have been done to improve flow at rpm

Offline 660magnum

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Re: Dual Port Muffler Experiments
« Reply #16 on: May 14, 2014, 04:41:31 pm »
I once had a Stihl 031 and it had a tube up through the muffler also.
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
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Offline KilliansRedLeo

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Re: Dual Port Muffler Experiments
« Reply #17 on: May 24, 2014, 04:24:20 pm »
OK have ran some quick tests of the three shown in the picture above with no other mods, used same saw for all tests tuned for break-in at 12.2K. Mufflers were all AM top exit type and had no obstructions internally except the pipes for the bolts. Secondary vents were all positioned to protrude the same distance into the muffler. Length of pipe did not make much of a difference excepting that the saw spun-up much quicker however saw is not yet broken in. Oh yeah, the sucker will make your ears ring, not really the object of what I am doing. The saw is a 365SP with BB kit (52mm), Stihl 064 piston and a single base gasket. Next will try all three again, with the addition of a small copper plate which replaces the spark screen and effectively blocks the escape of exhaust from the factory outlet this will force the tubular outlet to function as a tuned pipe. However I believe the pipe diameter and length will limit the pipes' ability to function properly as a tuned pipe.

Also have spoke to a few old motorcycle buddies and we have come up with a design that should function properly as a tuned pipe. Still will use the 0.800 ID pipe as well as 0.500 ID pipe. (The 0.500 ID pipe is the one we have the highest hopes for) I will be extending the length of the pipe to between 3.75 to 4.25 inches of OA length with as much of the pipe inside the muffler as the muffler design will allow while still keeping the internal entrance to the pipe a minimum of the pipe ID away from corners, walls and any other obstructions within the muffler. The factory exhaust outlet will be blocked off for these tests because in order for a tuned pipe to function, it must be the ONLY outlet.
"When the people fear the government...you have tyranny....When the government fears the people....you have liberty"

Thomas Jefferson
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Offline weimedog

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Re: Dual Port Muffler Experiments
« Reply #18 on: May 25, 2014, 11:19:05 pm »
This will be interesting! I've put 3/4 in dia tubes approx. 2.5 inches long in several mufflers. Always blocked off the stock. Problem is quantifying which of the mods made the most difference.... compression changes.... intake port mod... muffler mod...which ones? Have a 350 vid coming out in a bit. Found out a 1194 no base gasket build makes a significant difference.... or was it the muffler mod???  When its up take a look and maybe you can figure it out!

Offline KilliansRedLeo

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Re: Dual Port Muffler Experiments
« Reply #19 on: May 26, 2014, 11:34:20 am »
OK, quickly tested the 0.500 pipe late yesterday, it appears to be doing what we expected. Saw tops out (no load) @~11K, pulling bar/chain ~10.5. Tomorrow will put it in some green wood @ BIL's house. The objective of this was to see if we could keep the saw between max torque and max HP range with the tuning of the pipe. The saw will turn more RPM with the 0.800 pipe 12.5K but at that it has already fallen below max HP revs.

Our numbers indicated a 3.75 inch long pipe @0.500 diameter, however I left the pipe long (4.25 inches) so that I could take material off the pipe to see what changes it would make.

Got a BB kit coming from China, going to put it on 'Rat-Saw' with no other mods and see what happens with the tuned pipes. Then delete the base gasket and test again, then take it apart and try a Stihl 038 Magnum piston and test again......Should be fun!
"When the people fear the government...you have tyranny....When the government fears the people....you have liberty"

Thomas Jefferson
1743-1826

 

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