Muffler Mod Where and How Much?

[ballisticdoughnut]

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

Back pressure has nothing to do with scavenging. It does kill performance though. Your referring to pressure wave tuning, and chainsaw mufflers do a terrible job at it. I’m not saying go drill a gigantic hole in your muffler and call it a “mod”. Enlarging the factory outlet to 70% of exhaust port area is plenty.

 

[C George]

Pretty much all engines except blown ones need the correct back pressure to make good power

 

[thompsoncustom]

there is a thread on here somewhere where a member "timberwolf" I believe, took a muffler and welded it shut and then did tested slowly opening it up a little at a time and testing. if I remember correctly up to 170% of the bore was great for gains bit after that it had issues idling and most of those gains where made by 125% of the bore.

he did take it all the way to 400% of the bore and it made the most power but it was only like 10% more then 170%.

 

[ballisticdoughnut]

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

True. That’s why most of my saws are from early 80’s to mid 90’s. Good old piston ported power. Only strato saw I own is a 545 Mark II.

 

[C George]

The Stihl O series saws run great

 

[WheelHorseFan]

Simple muffler mods will give you a little more power, make the saw breath better and sound louder... port and polishing the cylinder head will give you more. An unlimited coil helps too. Decking/squashing the cylinder and other machining techniques will go further if done right... then we get into race saws with nitrous, methanol and tuned pipes....

Race saws with Nitro?
Wait' now how you hold on through the 1/8th mile? Good thing thay shortened tracks from 1/4 mile.
I never saw their point there, but now I saw why they went'n did it. I didn't see da saws, prolly just too fast to see'm.