Muffler Testing on a ported 660 - need opinions!

[Keith Gandy]

well I can't explain why that - modified baffle - tri port muffler does so well. But it does, and this isn't the first time or the first saw that i've tried it on. But it has been faster almost every time. I'd like to know why. The answer isn't just tune.

my only problem with it is it runs a little bit hotter. Not much.


Anyway there is something to it. Just can't figure it out and it pisses me off! lol

I think it depends on the porting and velocity behind it

 

[Mastermind]

well I can't explain why that - modified baffle - tri port muffler does so well. But it does, and this isn't the first time or the first saw that i've tried it on. But it has been faster almost every time. I'd like to know why. The answer isn't just tune.

my only problem with it is it runs a little bit hotter. Not much.


Anyway there is something to it. Just can't figure it out and it pisses me off! lol




only true way IMO is to make cuts on a big 30x32" cant with new chains every 100rpm til you find the best. I did that with the TM880 and MM084 in logs and the optimal wasn't where anyone that watched the vids thought it should of been.

I'm gonna go out on a limb and say the the OE designers know more than we like to credit them with. Those baffles provide a reflective back pressure that does more than we understand.

On tune........fatter is normally faster in large wood. Everyone is like "lean it on out". And.....they are wrong. lol

 

[Keith Gandy]

I'm gonna go out on a limb and say the the OE designers know more than we like to credit them with. Those baffles provide a reflective back pressure that does more than we understand.

On tune........fatter is normally faster in large wood. Everyone is like "lean it on out". And.....they are wrong. lol

So do u think its the baffle more than the sizes of the openings after the baffles?

 

[Moparmyway]

I find the best rpm while cutting and wherever it ends up is where I leave it.

I usually tune after 3 or 4 large cuts, and can usually find +/- 300 rpm under load

 

[Redbull661]

I'm gonna go out on a limb and say the the OE designers know more than we like to credit them with. Those baffles provide a reflective back pressure that does more than we understand.

On tune........fatter is normally faster in large wood. Everyone is like "lean it on out". And.....they are wrong. lol

this is what I think as well...

baffle in = you get the back pressure. but it holds in too much heat. Interesting thing is... unless you drill in that 1/2" hole where I have it. It's no where near as fast. I started at 1/4" hole and it got way faster and then solid, then I went to 1/2" and it got even faster yet. But only as a tri port. If you have only have the ported front cover and not that extra side port it's not good.


But if you take the baffle out, then I think you gotta get the back pressure from a solid/no port front cover. I kinda confirmed this for myself when I tried putting a opening/port on the 661 front cover...doesn't work out so well.


To me the bi port + solid/no port cover makes the most sense.

back pressure - from the solid/no port front cover

flow - equally placed and equally sized ports/holes. ...and you can go too big. 3/4-7/8" seems to be pretty nice.

screen size - the narrow weave seems to hold in too much heat as the 2nd cuts are always slower. The wide screens the cuts are much more consistent.


NOTE - I personally believe this back pressure thing is uber important only for the long bar. Seems if your doing short bar stuff you almost don't want a muffler at all... Don't quite understand it but these have been my observations.

 

[mdavlee]

The reason they need more fuel for longer cuts is the carbs are undersized to begin with.

 

[junkman]

A little more heat ain't so bad, heat produces power to a point. And is most likely burning the mix better

 

[Mastermind]

So do u think its the baffle more than the sizes of the openings after the baffles?

I really don't know Keith. I wish I have more good answers brother. You might have noticed that I don't weigh in as often as I once did. Seems like I have more questions than answers these days.

 

[Brewz]

Another factor to consider with increasing air out flow is air inflow.

The air filter could be holding things back?
Stock air filters are not so great

If your running a HD2, give it a good soak and clean in hot soapy water to remove the fines.
They can look clean but suffocate the saw

 

[Deets066]

this is what I think as well...

baffle in = you get the back pressure. but it holds in too much heat. Interesting thing is... unless you drill in that 1/2" hole where I have it. It's no where near as fast. I started at 1/4" hole and it got way faster and then solid, then I went to 1/2" and it got even faster yet. But only as a tri port. If you have only have the ported front cover and not that extra side port it's not good.


But if you take the baffle out, then I think you gotta get the back pressure from a solid/no port front cover. I kinda confirmed this for myself when I tried putting a opening/port on the 661 front cover...doesn't work out so well.


To me the bi port + solid/no port cover makes the most sense.

back pressure - from the solid/no port front cover

flow - equally placed and equally sized ports/holes. ...and you can go too big. 3/4-7/8" seems to be pretty nice.

screen size - the narrow weave seems to hold in too much heat as the 2nd cuts are always slower. The wide screens the cuts are much more consistent.


NOTE - I personally believe this back pressure thing is uber important only for the long bar. Seems if your doing short bar stuff you almost don't want a muffler at all... Don't quite understand it but these have been my observations.

Unless I read the results wrong.... Wasn't the tri-port no baffle the fastest and the coolest?

 

[Deets066]

This works for me

 

[Keith Gandy]

A little more heat ain't so bad, heat produces power to a point. And is most likely burning the mix better

Ive always seen it that way also

 

[Keith Gandy]

I really don't know Keith. I wish I have more good answers brother. You might have noticed that I don't weigh in as often as I once did. Seems like I have more questions than answers these days.

I hear u man! Theres alota fellows on here that r sharp as a tack and alot that r sharp and never hardly say a word. Folks that come to mind that have put in their time, learned, and r a wealth of knowledge , Mastermind, Treemonkey, Mdavlee, Jason, Scarr52, StihlBro, Junkman, Moparmyway, Redbull, Deets, Definative Dave as well as many others. Redbull has put in so much time testing that its unreal and he has so much packed in that head that I dont know how he does it? I know he takes good notes but he sure deserves credit bringing forth alota good info

 

[jmssaws]

Generally all testing does is confuse the party involved,everytime I test anything i come away with a headache.

The way a muffler is done needs to match the porting in the cylinder,the muffler that works best on randy's or Scotts saws may not be the best for somebody else's, there is absolutely nothing that's across the board.

 

[jmssaws]

Million ways to screw this pony and none of them are necessarily wrong.

 

[Keith Gandy]

Generally all testing does is confuse the party involved,everytime I test anything i come away with a headache.

The way a muffler is done needs to match the porting in the cylinder,the muffler that works best on randy's or Scotts saws may not be the best for somebody else's, there is absolutely nothing that's across the board.

I agree Jason. What would u say u consider when sizing the outlet? Is velocity, blowdown, etc. ?

 

[jmssaws]

I agree Jason. What would u say u consider when sizing the outlet? Is velocity a key?

Depends on how much you can get through the carb.
When you start porting the hell out of one the carb becomes the limiter fast and you have to match the muffler to it or you will pump out more than you can suck in.
Get more through the intake and transfers then you can get more out the muffler.
It all has to work together or one end or the other will be hurting you.
That's my thinking right now but by tonight it may have changed.

 

[Keith Gandy]

Depends on how much you can get through the carb.
When you start porting the hell out of one the carb becomes the limiter fast and you have to match the muffler to it or you will pump out more than you can suck in.
Get more through the intake and transfers then you can get more out the muffler.
It all has to work together or one end or the other will be hurting you.
That's my thinking right now but by tonight it may have changed.

Sounds right on Jason! I guess I try and think about moving air from start to finish and how each passage size affects each other

 

[Brewz]

I have 3 large outlets on mine but I have this to make up for the fine screens that are fairly compulsory when cutting in the dry dusty conditions usually encountered here.
I have never seen snow in my 41 years, but seen more dry dead dusty grass and bark that I care to remember.

When I first opened up the muffler I noticed a bit of a gain but nothing special.
When I fitted up a really free flowing air filter it stepped up again.

I might have a play with my 064 and 066 and slip a piece of plate in the front muffler outlet to clock it off and see what it does.

 

[the BMOC]

I would like to take a minute and thank red bull for the time, energy and money that he puts into these tests. Members like him are making the online chainsaw forum community a better place.

It's easy to get online a spout things that may or may not be true. But @Redbull661 and others like Chris-pa (who has gone so far as to develop some very cool software) and Snelling (who tirelessly documents his exploits with pics and vids) really make this community like no others.

Thansk-you.