Part Six: The Exhaust System

[Deets066]

It’s about flow, one big outlet flows more than numerous small ones

 

[Fruecrue]

It’s about flow, one big outlet flows more than numerous small ones

Is this too many?

 

[Dub11]

Is this too many?
View attachment 164504

Nope you need a few more under that Y to even it out some.

 

[huskihl]

It’s about flow, one big outlet flows more than numerous small ones

Works on exhaust ports.


Women not so much

 

[RI Chevy]

Is this too many?
View attachment 164504

I think you need a new clutch with dat!

 

[Master Bud II]

It would sound REAL good if I fired my 064 up and let it idle with em. It has a mean pop like a 288

View attachment 69185

What Tubing did / Do you Use ???
Bud

 

[Deets066]

What Tubing did / Do you Use ???
Bud

Rigid pipe, I think that one has a 1” pipe on one side and 1-1/4” on the other

 

[00wyk]

Look, man! I ain't fallin fo no banana in my tailpipe!

 

[Lightning Performance]

What I find most interesting is the exhaust ports ability to work with many different outlets and the torque made or taken away by "tuning" the muffler. Does enlarging the port volume help or hurt torque? One will never know without enough outlet area. I'll try a stock port on my mill saw. It will be operating at far less rpm in the cut than most saws run at while bucking wood. In theory, more time should require much less area to perform well

 

[RI Chevy]

I think @tree monkey already experimented with a Stihl saw and found more was better. Ported saw of course.
@mustang mike thinks along your ways Kenny. He claims to loose some torque by going to big.

 

[Ketchup]

I seem to get more RPM by going higher, but can maintain more compression and torque by widening. Too much of either is a bad thing.

 

[Mastermind]

I've been messing with saws too long.

 

[RI Chevy]

Any of this make sense BOSS?

 

[deye223]

It's kinda turned in to a deflector thread .

 

[RI Chevy]

We DERAIL with the best of them...[emoji2957]

 

[Ketchup]

What I find most interesting is the exhaust ports ability to work with many different outlets and the torque made or taken away by "tuning" the muffler. Does enlarging the port volume help or hurt torque? One will never know without enough outlet area. I'll try a stock port on my mill saw. It will be operating at far less rpm in the cut than most saws run at while bucking wood. In theory, more time should require much less area to perform well

Sorry, I should have read back a little farther. I thought you meant cylinder exhaust port.

Seems to me a stock muffler gets filled with exhaust almost immediately. If the muffler outlet is smaller than the exhaust port, some degree of back pressure will result. Relative location of ports and muffler volume will also create more or less resistance.

I only see 2 useful qualities to back pressure on a non piped saw. Strato saws may benefit from mixing cold air and fuel charge in the compression chamber. Back pressure may also
prevent fresh charge from going out the exhaust.

My question about many small muffler ports comes from this. I was thinking you could open an increasing number of holes until the optimum pressure was reached. It’s easier to plug a small hole than back fill part of a large one. I’m now thinking an adjustable gate would be a good way to figure out optimum port area and then that area could be designed in permanently.

The multiple small holes might still be useful for making quieter power.

 

[Lightning Performance]

Sorry, I should have read back a little farther. I thought you meant cylinder exhaust port.

Seems to me a stock muffler gets filled with exhaust almost immediately. If the muffler outlet is smaller than the exhaust port, some degree of back pressure will result. Relative location of ports and muffler volume will also create more or less resistance.

I only see 2 useful qualities to back pressure on a non piped saw. Strato saws may benefit from mixing cold air and fuel charge in the compression chamber. Back pressure may also
prevent fresh charge from going out the exhaust.

My question about many small muffler ports comes from this. I was thinking you could open an increasing number of holes until the optimum pressure was reached. It’s easier to plug a small hole than back fill part of a large one. I’m now thinking an adjustable gate would be a good way to figure out optimum port area and then that area could be designed in permanently.

The multiple small holes might still be useful for making quieter power.

Or tune by using different size screens in the exit holes

 

[MG porting]

We DERAIL with the best of them...[emoji2957]

Yea tell me about it!!!

 

[MustangMike]

Clarification … I said it works on "some" saws, not all. I think it depends on a lot of other factors, but I have seen a few 660s that prefer a modified baffle (rather than just removing it). I have other 660s that don't like the modified baffle.

I think it has something to do with the saws porting, and more specifically blowdown, but I don't pretend to have all the answers, I'm just posting my observations and trying to learn.

Also note that in TM's testing it was a fully ported saw, and all of his outlets are screened (which result in about 50% less flow). Most of my saws are not screened.

Back pressure may also
prevent fresh charge from going out the exhaust.

I believe this is what was happening on some of my saws.

 

[~WBF]

Possible as many variables as sharpening and filling through different activities and species of wood. Everything has a different outcome.

Has there been any consideration between hard rubber mounts and AV mounts from you engineers in relation to back pressure? Do you build them different? or build them so it works for both? or you guys just here learning?.