ported 661 baffle in muffler vs baffle out

[Moparmyway]

 

[Deets066]

Sounds like Keven has done the proper muffler testing (with each one producing more power in the cut) so that my concern IS NOT VALID HERE.

And DEETS and Keven are both right that a 2 cycle is not real efficient, and it will always release some unburnt fuel, and the IN GENERAL the more power you produce the more unburnt fuel will be released.

That said, the premise that excessive unburnt fuel will always produce more power is FALSE, and I believe TM has commented on it in the past.

A 2 cycle engine is not just a constant flow, it is a series of pulses (all engines are), and when your components are in sync it will run better. There are situations when some additional back pressure will produce more power.

There are times when excess unburnt fuel being drawn into the muffler will cost you power. Fuel remaining in the combustion chamber will produce more power than unburnt fuel in the muffler.

Even a tuned pipe has a very large expansion chamber and a small outlet. Think about why that is. To listen to Kevin and DEETS, you would think no muffler at all would out perform a tuned pipe, but that is not the case.

Tuned pipe is the most efficient and makes the most power because it puts hot atomized fuel back in the chamber.

maybe we could drill a couple 1/4” holes in the side of the pipe to make ultimate power?

 

[Deets066]

Dang, these are some crazy ideas for my MM only kind of mindset, and I like em.

Don’t do that, it was just a little jab at mike

 

[MustangMike]

Tuned pipe is the most efficient and makes the most power because it puts hot atomized fuel back in the chamber.

Now how could it do that, except with back pressure?????? Hymmmmm.

 

[huskihl]

Now how could it do that, except with back pressure?????? Hymmmmm.

Backpressure at exactly the right time right before the exhaust closes... from 26” away

 

[Deets066]

Now how could it do that, except with back pressure?????? Hymmmmm.

TUNED back pressure.
FFS

 

[MustangMike]

Yes, and "untuned" back pressure will not work as well, but it may provide some benefit.

It is the same reason many builders will not open up the front cover, just the sides, and usually the closer to the motor the better.

As I stated previously, the desired opening will often depend (partly) on the port work.

 

[Moparmyway]

Now how could it do that, except with back pressure?????? Hymmmmm.

Yes, and "untuned" back pressure will not work as well, but it may provide some benefit.

Mike, I think you are on to something here !!


I’m going to have THE most efficient 394/395 on the planet !!!

Should be nuts with all the torque too, unless if’n you think the openings are too big ????

 

[MustangMike]

Funny Kevin.

I've never said the factory outlets were large enough, and I don't own any saws that do not have larger holes, but on some saws there is a point of diminishing returns.

I know you build some really strong saws, and I respect your work and your opinions, but on this matter we will just have to disagree.

Let's move on.

 

[Deets066]

Mike, I think you are on to something here !!


I’m going to have THE most efficient 394/395 on the planet !!!

Should be nuts with all the torque too, unless if’n you think the openings are too big ????




View attachment 237187 View attachment 237188

I bet that sounds awesome.....

 

[MustangMike]

Mike, I think you are on to something here !!


I’m going to have THE most efficient 394/395 on the planet !!!

Should be nuts with all the torque too, unless if’n you think the openings are too big ????




View attachment 237187 View attachment 237188

Presuming you have the original factory outlet in addition to your two "horns", you now have the perfect test bed for your saw!

Don't forget to re-tune it, and do some timed cuts and see if your popping goes away.

Then, gradually increase the size of the holes and re-tune and do more timed cuts, and see if the times keep increasing and when the popping returns (presuming it goes away in the first place).

FYI, my recommended 2 - 1/4" holes are for relatively stock 440 and 460/461 saws. I open things up more on larger saws, and predict a ported 395 will need much larger openings.

Will be interesting to see the results.

 

[CR888]

I've taken a few deep breaths the last couple of pages and refrained from commenting.

Now how could it do that, except with back pressure?????? Hymmmmm.

Tuned pipes work on resonance waves that both push and pull exhaust gasses even drawing unburnt charge into the pipe then stuffing it back into the cylinder just at the right moment. Its an acoustic sound wave resonance that is reflected pushing back charge into the cylinder. This is why idiots who think they can turn their can style saw muffler into a tuned exhaust are bonkers because they don't grasp the basic physics of the situation. Tuned pipes are big fat and long because they have to be, you can't change the speed of a resonant wave so it needs time to exit the exhaust and bounce back off the diffuser cone and return back through the header into the cylinder at the right time for it to be effective. Yes some back pressure is needed but the magic of the expansion chamber exhaust lies in its use of sonic resonance. But anyways...carry on.

 

[CR888]

Pitchas make the basics easier to grasp.

 

[MustangMike]

Great stuff, thanks for posting, it is very informative.

I stated in a previous post that a tin can muffler can never do what a tuned pipe does.

That said, this also demonstrates that the unrestricted flow of exhaust does not always provide the most power, and anyone who has seen a good running piped saw knows that.

While waves bouncing off the inside cover of a muffler will never result in the push back that a pipe can generate, they may stall the escape of some unburnt fuel enough to provide some additional power.

The venting of the muffler will always effect the RPM at which this is most effective. It is just far less effective and much cruder than a tuned pipe.

As I previously stated, it is a series of pulses, not a continuous flow. Timing is everything, and when you open up a muffler it may got through cycles of better and worse (the power change may not be linear).

It is similar to handloading for a rifle. Every barrel whips. If you can find a load that exits the barrel at either the top or bottom of the whip, your accuracy will improve.

This seems so clear to me that I'm very frustrated that I have not been able to explain it effectively. My apologies for that.

 

[Moparmyway]

FYI, my recommended 2 - 1/4" holes are for relatively stock 440 and 460/461 saws. I open things up more on larger saws, and predict a ported 395 will need much larger openings.

Twas installed on a brand new, 100% stock 395 that was ran at the CT GTG, 7 tanks of fuel !

but on this matter we will just have to disagree.

Let's move on.

Presuming you have the original factory outlet in addition to your two "horns", you now have the perfect test bed for your saw!

Don't forget to re-tune it, and do some timed cuts and see if your popping goes away.

Then, gradually increase the size of the holes and re-tune and do more timed cuts, and see if the times keep increasing and when the popping returns (presuming it goes away in the first place).

FYI, my recommended 2 - 1/4" holes are for relatively stock 440 and 460/461 saws. I open things up more on larger saws, and predict a ported 395 will need much larger openings.

Will be interesting to see the results.

That said, this also demonstrates that the unrestricted flow of exhaust does not always provide the most power, and anyone who has seen a good running piped saw knows that.

While waves bouncing off the inside cover of a muffler will never result in the push back that a pipe can generate, they may stall the escape of some unburnt fuel enough to provide some additional power.

The venting of the muffler will always effect the RPM at which this is most effective. It is just far less effective and much cruder than a tuned pipe.

As I previously stated, it is a series of pulses, not a continuous flow. Timing is everything, and when you open up a muffler it may got through cycles of better and worse (the power change may not be linear).

Mike, I've stayed silent for a little, outta respect, Imma gunna keep this short and sweet ................. YOU dont seem to want to move on.

Its your thread, I'm out

 

[huskyboy]

I see a whole lotta talking theory in this thread from everyone and no testing videos. Maybe I should test... it’s just time right?

 

[huskyboy]

It appears that some stock and ported testing has already been done. At least on one particular saw. The ms461.

I have a mastermind 461 here, that I might test muffler outlet with to see if I get similar results. It tunes nice and easy. The muffler covers are cheap and easy to remove. Has a unlimited coil... these things make the testing process much easier for me.

 

[MustangMike]

If you go to that first video (which is in hardwood) at about 3 min in they say taking the baffle out hurt, and then they added another port and the difference was only 1 tenth of a second (I would call that a tie).

So, having some baffle in some saws can HELP, confirms what I've said with my Asian 660 testing (on unported jugs). My ported jugs prefer a complete removal of the baffle.

Sorry if this is painful for you Kevin, not what I intended, but when I said I would move on you posted something indicating I was a clueless nut that didn't understand what was going on.

The TM testing indicates otherwise. Thank you Mason, Scott + Julian.

 

[MustangMike]

The results will be different on different saws and in different wood.

When I was playing with that Asian 660 (one of my Asian twins) the saw with the baffle removed revved higher, had quicker throttle response and sounded like it would destroy the other saw.

But I was cutting a large, old (near petrified) round of Chestnut Oak, and the saw without the baffle just seemed to fall on it's face in the cut. I changed out the muffler for one that was just like the one on the first saw and the torque came back, just like in the TM video.

I was in the woods, alone, and did not video my testing, but it was a significant enough difference that I knew it right away. You just could not lean on the saw with the baffle removed like you could when it just had a modified baffle.

Perhaps, in softwood, the results would have been different.

 

[huskyboy]

Ms661 muffler cover on and muffler cover taken off. So it seems like you do go backwards at some point... the question is when? My thoughts are that saws run better and idle better with side exits vs DP covers/big openings on the front of the muffler. But testing will have to prove that theory.