Muffler Mod Where and How Much?

[C George]

Are you proficient at sharpening a chain, great gains to be found there. If you can't sharpen a chain well, any gains seen thru modding a muffler will be lost.
Also you will need to test the mods you make before and after to see if you gained anything or just made it louder, louder isn't always faster, and higher rpm doesn't always correspond to a saw that's easy to keep in the sweet spot.

Agree , id much prefer to open up the intake for power vs the exhsust

 

[ballisticdoughnut]

Agree , id much prefer to open up the intake for power vs the exhsust

If the idea is to increase performance, you have to move air. The weakest link in the chain in that respect is the muffler. To get more air in you need to get more air out. In order to do that your gonna have to live with a little more noise.

 

[freeasaburt]

Something else I was wondering about: do stock, constricted mufflers also help with scavenging, or are they mainly there to make the saws quieter and EPA compliant? In other words, is scavenging actually a thing when it comes to these small, 'box type' chainsaw mufflers, or only when long pipes with an appropriately shaped 'belly' are put unto 2 stroke engines?
If it's a thing, I suppose fuel efficiency will decrease a bit when you open up the muffler? I don't mean the consumption per hour, but the amount of fuel needed to do a specific amount of work.

I've seen the topic mentioned here and there but didn't find a definitive answer yet.

 

[C George]

If the idea is to increase performance, you have to move air. The weakest link in the chain in that respect is the muffler. To get more air in you need to get more air out. In order to do that your gonna have to live with a little more noise.

Yes but most 2 stroke intakes , especially many Stihl pieces of eq. that I work on are highly restricted for long service life

 

[C George]

Something else I was wondering about: do stock, constricted mufflers also help with scavenging, or are they mainly there to make the saws quieter and EPA compliant? In other words, is scavenging actually a thing when it comes to these small, 'box type' chainsaw mufflers, or only when long pipes with an appropriately shaped 'belly' are put unto 2 stroke engines?
If it's a thing, I suppose fuel efficiency will decrease a bit when you open up the muffler? I don't mean the consumption per hour, but the amount of fuel needed to do a specific amount of work.

I've seen the topic mentioned here and there but didn't find a definitive answer yet.

If you decrease the backpressure too much the engine will loose both torque and rpms ,, crazy how a can muffer even gets close to 10k

 

[C George]

Why all Hot Saws run a lengthy " tuned pipe"

 

[C George]

Why all Hot Saws run a lengthy " tuned pipe"

Same as a Race dirt bike or snowmobile , thats when you here the real Snap thru the pipe

 

[thompsoncustom]

Why all Hot Saws run a lengthy " tuned pipe"

it's like a turbo for a 2 stroke by pulling more fuel into the exhaust and bouncing it back in the cylinder you can add air/fuel volume.

there's a dyno video on YouTube where they take a stock ms660 and put a pipe on it and it goes from something like 7.5hp to 12hp with no other mods.

 

[freeasaburt]

Same as a Race dirt bike or snowmobile , thats when you here the real Snap thru the pipe

Yeah the way I understand it is you tune the reflecting pressure waves to 'suck back' (ha! it's a bad choice of words, on purpose as it's a reference to another, quite popular thread here) unburned fuel/air mix.

 

[freeasaburt]

it's like a turbo for a 2 stroke by pulling more fuel into the exhaust and bouncing it back in the cylinder you can add air/fuel volume.

there's a dyno video on YouTube where they take a stock ms660 and put a pipe on it and it goes from something like 7.5hp to 12hp with no other mods.

I read that a 125cc four stroke engine can actually burn +/- 110cc of mix, whereas a 125cc with proper scavenging can burn about 180cc.

 

[Farmer_Nate]

People talk a lot about mufflers and restrictions. However, I thought it was harder to suck air than it was to blow air, so-to-speak. I think perhaps intake gets too little attention. I think exhaust gets too much attention. Exhaust has a lot of pressure, so it should be able to move air no matter what, even with a bit of restriction.

Intake is under vacuum, and a limited amount of vacuum is possible, so it seems to me more attention should be paid to smoothing and enlarging intake. I have noticed gains by gutting mufflers, but I wonder what more could be done with more intake work. Might there be a market for aftermarket larger intake runners, for instance?

Just a thought.

 

[C George]

it's like a turbo for a 2 stroke by pulling more fuel into the exhaust and bouncing it back in the cylinder you can add air/fuel volume.

there's a dyno video on YouTube where they take a stock ms660 and put a pipe on it and it goes from something like 7.5hp to 12hp with no other mods.

I totally believe it as my son and I ride 2 stroke dirt bikes

 

[C George]

People talk a lot about mufflers and restrictions. However, I thought it was harder to suck air than it was to blow air, so-to-speak. I think perhaps intake gets too little attention. I think exhaust gets too much attention. Exhaust has a lot of pressure, so it should be able to move air no matter what, even with a bit of restriction.

Intake is under vacuum, and a limited amount of vacuum is possible, so it seems to me more attention should be paid to smoothing and enlarging intake. I have noticed gains by gutting mufflers, but I wonder what more could be done with more intake work. Might there be a market for aftermarket larger intake runners, for instance?

Just a thought.

100% true , I have seen huge differences in power on smaller saws by just uncorking the intake

 

[Farmer_Nate]

I have been known to do a little dremel work to plastic intake runners. The ones I have played with had surprising numbers of flash, sharp corners and stuff that hurts flow. I also found thicker regions that could be thinned to increase cross sectional area.

 

[C George]

I have been known to do a little dremel work to plastic intake runners. The ones I have played with had surprising numbers of flash, sharp corners and stuff that hurts flow. I also found thicker regions that could be thinned to increase cross sectional area.

like this Stihl blower intake ?

 

[Farmer_Nate]

Wow, that should do it!

 

[C George]

I was able to adjust carb to put plenty of fuel to it and this sucker really blows some leafs

 

[C George]

Wow, that should do it!

besides the smaller hole , the intake air had to follow the molded runners , but again built for a long service life

 

[Farmer_Nate]

So, "de-tuning" makes them make less power, and last longer? That's not much fun!

 

[Campbellcontractlogging]

If the idea is to increase performance, you have to move air. The weakest link in the chain in that respect is the muffler. To get more air in you need to get more air out. In order to do that your gonna have to live with a little more noise.

That’s not technically true with a 2 smoker you need sufficient back pressure with scavenging effect.