Show off your muffler mods

[Bjorn]

Look here

 

[Mastermind]

What size rive nuts do you guys use for the deflectors? Thinking about trying that route on my 350 muffler.

4mm

 

[whitesnake]

What size rive nuts do you guys use for the deflectors? Thinking about trying that route on my 350 muffler.

M4 rivnuts here

 

[millerlite]

Just read a pile of this thread and have a rant to add.

You 100 percent can turbo a piston ported 2 stroke. A properly sized turbo has turbine drive pressure less than boost or 1:1 typically, but during spool it is more like 3:1. Regardless, you are basiclly buulding a 2 stroke that essentially runs at a higher atmospheric pressure.

Example, we are sitting in around 15 psi at sea level. At 15 psi boost, the exhaust drive pressure is around 15 psi, making the motor 'see' 30 psi absolute on the intake and the exhaust. Even if the exhaust or intake pressure doesnt match, it still "works" due to how a 2 stroke works in the first place. Youre essentially just increasing atmospheric pressure. When you go from 4000 ft to sea level does your saw all of a sudden defy physics and fail to run? A stock muffler has far more backpressure than atmospheric pressure, like a turbo during spool. Does the saw just quit? Nope its just running at less volumetric efficiency.

The issue is why turbo a saw? Turbos are heavy, have packaging constraints, and something appropriately sized doesnt exist unless you are talking 140cc plus saws.

My take on pipes and muffler mods is there is obviously science involved. There are noise harmonics and waves bouncing around. There are also pressure and temperature gradiants. Air, exhaust, etc. All has a mass and hence kinetic energy when its flowing. As you know accelerating a decelerating mass takes energy and time. Additionally in a two stroke, you want some back flow at the appropriate time to act as an exhaust dam. I've built a lot of whacko exhausts from mufflers to pipes. You just cant predict whats going to work the best unless you run it. A dyno is beneficial and likely is my next project.

 

[Stump Shot]

395XP with @tree monkey large deflector with a Husqvarna screen and Stihl exhaust gasket. All three line up perfectly and work together perfectly. The gasket ensures a better seal. as well as reducing screen vibration, this increasing it's longevity. Attached with 5mm rivnuts and stainless steel screws with a dab of hi temp loctite.

 

[59billy]

395XP with @tree monkey large deflector with a Husqvarna screen and Stihl exhaust gasket. All three line up perfectly and work together perfectly. The gasket ensures a better seal. as well as reducing screen vibration, this increasing it's longevity. Attached with 5mm rivnuts and stainless steel screws with a dab of hi temp loctite.

View attachment 469084

What I like is that it looks like it came from the factory that way.

 

[oddsaws]

Freshly baked 346xp mufflers

 

[Junk Meister]

Freshly baked 346xp mufflers

View attachment 474079

SUGAR FREE???

 

[Ezarb]

Came across this 661 experiment from back in 2018.

Thread '661 muffler mod progression w/thermocouple'

Jan 5, 2018

Did this back on Dec 1st when it was still warm. Now that it's -22 and I don't want to go outside...

This is a completely stock 661 with 10 tanks on it. I am running 8pin 114dl RSK.

• Redbull661
• Replies: 15
• Forum: Chainsaws

• 

My question here is -
Are the Bark Box style MM on 661's considered useless as far as gains go due to them not being traditional side ports?

(Sorry if this has been beat to death already as i dont have the time to scroll 182 pages, yet I cannot for the life of me figure out a way to search basic keywords within specific threads)

 

[Shane¹]

Muffler modded up for 350 build

 

[bogieboy]

Came across this 661 experiment from back in 2018.

Thread '661 muffler mod progression w/thermocouple'

Jan 5, 2018

Did this back on Dec 1st when it was still warm. Now that it's -22 and I don't want to go outside...

This is a completely stock 661 with 10 tanks on it. I am running 8pin 114dl RSK.

• Redbull661
• Replies: 15
• Forum: Chainsaws

• 

My question here is -
Are the Bark Box style MM on 661's considered useless as far as gains go due to them not being traditional side ports?

(Sorry if this has been beat to death already as i dont have the time to scroll 182 pages, yet I cannot for the life of me figure out a way to search basic keywords within specific threads)

My anecdotal evidence is that a bark box style muffler did help my 661 breathe better, and therefore has more oomph in the cut, however, thats all anecdotal evidence, and thats on a ported 661, not stock, and testing was not done back to back, on the same log, same day type of scenario... also was swapped out while still breaking in the new cylinder and piston....

 

[Ketchup]

Came across this 661 experiment from back in 2018.

Thread '661 muffler mod progression w/thermocouple'

Jan 5, 2018

Did this back on Dec 1st when it was still warm. Now that it's -22 and I don't want to go outside...

This is a completely stock 661 with 10 tanks on it. I am running 8pin 114dl RSK.

• Redbull661
• Replies: 15
• Forum: Chainsaws

• 

My question here is -
Are the Bark Box style MM on 661's considered useless as far as gains go due to them not being traditional side ports?

(Sorry if this has been beat to death already as i dont have the time to scroll 182 pages, yet I cannot for the life of me figure out a way to search basic keywords within specific threads)

I don’t have particular 661 knowledge here, but generally speaking it matters less how you open up the can, it matters how much. If a bark box has a 1” opening area and or you have 2 side outlets with deflectors that add up to 1” area, you’re going to get similar performance.

There are subtle particulars like two holes not flowing as well as one, or line of exit from the port to the muffler outlet. Piped outlets may have slightly more effect because they are an optimal circular shape and act like a straw, directing flow more specifically. But at the end of the day, it matters how big the hole is most of all.

Most of the other design elements of muffler outlets have to do with where the heat goes and how much noise comes out. You want the heat and toxic gas going away from the operator and not where it will scorch the saw or start a fire. Multiple smaller outlets are typically quieter as are saws with spark arrestors.

And none of it matters if the saw doesn’t need a bigger outlet. It just runs the same, but louder. The internal port sizes and timing will determine how much the muffler is holding the saw back. There are a lot of bolt on parts that claim performance, but they’re just lipstick on a pig. A Magnum sticker is quieter, cheaper and probably helps resale value more.

 

[Wilhelm]

At some point they merely get LOUDER.

My SLR muffler PS-7310 was a pig stock, tuned to shy of 12.8k rpm!
I disliked running her, I got headaches from the high pitched sound of her.
Once I gutted the muffler and merely increased the factory stock muffler outlet to where I could still utilize the stock spark screen she became a beast to my liking.
Mind You, factory stock PH, no porting, no TA, no BGD - merely cut the SLR tube out, increased the single stock muffler outlet and retuned her to just shy of 12.8k rpm.
She puts both my PS-7900's to shame!

There is a thing as too much.
Also, there is a thing called placebo effect.

 

[MustangMike]

I don’t have particular 661 knowledge here, but generally speaking it matters less how you open up the can, it matters how much. If a bark box has a 1” opening area and or you have 2 side outlets with deflectors that add up to 1” area, you’re going to get similar performance.

I will respectfully disagree. I've discussed this with porters who are far more knowledgeable than I am. A hole in the front of the muffler will reduce back pressure (sometimes too much) and result in more noise than performance. They prefer to add openings to the side to preserve some degree of back pressure. The exhaust should be a timed pulse, not just a flow.

In my own testing, sometimes fully removing the baffle from a non-ported MS660 will reduce torque dramatically. A 1/2" hole drilled in the front of the baffle will often work much better.

Every saw is different, so I don't presume that what works on one will work on all. Factory port timing is often all over the place.

 

[singinwoodwackr]

Came across this 661 experiment from back in 2018.

Thread '661 muffler mod progression w/thermocouple'

Jan 5, 2018

Did this back on Dec 1st when it was still warm. Now that it's -22 and I don't want to go outside...

This is a completely stock 661 with 10 tanks on it. I am running 8pin 114dl RSK.

• Redbull661
• Replies: 15
• Forum: Chainsaws

• 

My question here is -
Are the Bark Box style MM on 661's considered useless as far as gains go due to them not being traditional side ports?

(Sorry if this has been beat to death already as i dont have the time to scroll 182 pages, yet I cannot for the life of me figure out a way to search basic keywords within specific threads)

The bark box style covers have a pretty good deflector setup even though they are a front port. In general, they are just too damn loud, imo

It was interest to see the Tree Monkey style tri-port compared to the others. With well over 100% of the cylinder exhaust port I didn’t expect it to work that well.
Must have a lot to do with the ‘side port’ concept creating better back pressure as opposed to any type of front port or just enlarging an existing OE port.

 

[Ketchup]

The exhaust should be a timed pulse, not just a flow.

In my own testing, sometimes fully removing the baffle from a non-ported MS660 will reduce torque dramatically. A 1/2" hole drilled in the front of the baffle will often work much better.

Every saw is different, so I don't presume that what works on one will work on all. Factory port timing is often all over the place.

We might have to take this to a different thread because it’s a legitimate debate: Is back pressure valuable, or is it only helpful if the transfer scavenge loop or chamber compression is fundamentally weak? I see it both ways but I lean toward the second.

Back pressure may be relevant, but it’s into the details. Just like pipe vs deflector.

 

[singinwoodwackr]

We might have to take this to a different thread because it’s a legitimate debate: Is back pressure valuable, or is it only helpful if the transfer scavenge loop or chamber compression is fundamentally weak? I see it both ways but I lean toward the second.

Back pressure may be relevant, but it’s into the details. Just like pipe vs deflector.

And, what are the differences between ported and non ported saws when it comes to muf mods?

 

[Ketchup]

And, what are the differences between ported and non ported saws when it comes to muf mods?

A simple way to think about it is the muffler outlet restricts flow. If you open it larger than another restriction in the saw, you’ve made all the gains you can until you fix that constriction up stream.

Ported saws typically reduce restrictions through the whole system, so their rate of exhaust has to be big enough to handle that. Ported saws also generate more heat.

 

[huskihl]

Basically, the more outlet area you have, and the closer to being straight out, the more rpm and hp it will have. Torque on a dyno follows the hp curve, but felt torque goes down.

Run a stock stihl muffler in a timed cut with and without the front cover. And then run it on the dogs with and without the cover. Without the cover will win in smaller wood where you have enough torque to maintain the higher rpm. But will be much more forgiving on the dogs in bigger wood with the cover. It’s all about balance