why a muffler mod lowers internal engine temps

[timberwolf]

To really do this up right I think a dyno would be needed to produce repeatable loading as well as give more defined HP numbers, also would need an EG anylyzer to make sure the mixture was kept right on point while the exhaust opening was changed.

I can't see much science or logical arguement to support the idea of a closed up muffler resulting in a cooler running engine in a stock chainsaw. And what limited tinkering I did with it followed with increased opening and reduced back pressure resulting in cooler running and improved performance, down side is noise and fuel consumption that I am sure can be extrapolated to also meen increased pollution.

When it comes to ported saws, don't think there is anyway to get around it, making more power meens burning more, burning it faster, and burning it hotter. Almost everything that needs to be done to accomplish this generates more heat.

 

[BigSaw]

The timberwolf tests are really great, but there is little difference in "3 cut" cylinder head temperatures until the muffler is opened up to 6 times the factory size... I sure don't open mine close to that big...and won't.. and rarely see any that are, Part of it's job is to "muffle", and run well

Back to a world without orange and black snakes... It's not really making much difference at all! Stock (0.11sq.in.) 105C, (0.30sq.in) 96C, (0.45sq.in) 105C ...

I like to do some tests at more than "3 cut" totaling 6-7 seconds ; like mill a section of wood for 2 minutes. i.e. full continous HP, not three short bursts.

Really? would that satisfy you? Or would you then naysay, and find some other reason to dispute the evidence? There is a difference between running hotter as you keep telling people muffler mods do. and running cooler which all evidence before you supports. Why can't you admit that you are wrong? Are you that much of a retard?

 

[scotclayshooter]

To really do this up right I think a dyno would be needed to produce repeatable loading as well as give more defined HP numbers, also would need an EG anylyzer to make sure the mixture was kept right on point while the exhaust opening was changed.

I can't see much science or logical arguement to support the idea of a closed up muffler resulting in a cooler running engine in a stock chainsaw. And what limited tinkering I did with it followed with increased opening and reduced back pressure resulting in cooler running and improved performance, down side is noise and fuel consumption that I am sure can be extrapolated to also meen increased pollution.

When it comes to ported saws, don't think there is anyway to get around it, making more power meens burning more, burning it faster, and burning it hotter. Almost everything that needs to be done to accomplish this generates more heat.

Looks like someone is going to have to do some work to prove this one way or the other!
Hey TW any way to work out the difference in the CFM of the cooling fan at pre and post modded cutting speeds?
I run a FS250 strimmer thats muffler modded with the guards removed running extended line, It was mentioned on AS that this machine should be heat seizing!!! But it still runs for hours at a time on full throttle with only a rest to extend line and re-fuel!

 

[timberwolf]

Not easy as it's not positive displacement, but a fans like a pump and every vane type pump has a pump curve with an optimum speed for efficiency. If a motor was hopped up 10% in RPM over stock I would not expect to get 10% more air flow from the cooling fan but don't imagine it would be too much less than the 10% gain in RPM.

Would be easier just to measure the air speed over the fins at a few points and develop a curve. Thats how we do it for testing and certifying fire pump installations.

If your not getting good even cooling to the fins your doing it no favors. Just like air cooled 2 cyl sleds, it's the second cyl from the fan that takes the heat and often runs into problems, and it's often the fan side cyl that will foul a plug and act like it need an hotter plug.

 

[scotclayshooter]

Ok so what about the internals of the muffler? would it make any difference leaving the baffles in as in the lakeside 361 mod or taking it apart and gutting it out?
If the gas can escape at a faster rate without being buffeted about by the baffles would the muffler be cooler?

 

[Tzed250]

Really? would that satisfy you? Or would you then naysay, and find some other reason to dispute the evidence? There is a difference between running hotter as you keep telling people muffler mods do. and running cooler which all evidence before you supports. Why can't you admit that you are wrong? Are you that much of a retard?

alias...

 

[Gologit]

Really? would that satisfy you? Or would you then naysay, and find some other reason to dispute the evidence? There is a difference between running hotter as you keep telling people muffler mods do. and running cooler which all evidence before you supports. Why can't you admit that you are wrong? Are you that much of a retard?

The man isn't a retard at all. He's probably helped more people on AS than any other single member. His advice and his knowledge are always welcome...and always right on target .What are your creds? Besides being insulting and demeaning, that is.

By the way...I neg-repped your post. You earned it.

 

[scotclayshooter]

The man isn't a retard at all. He's probably helped more people on AS than any other single member. His advice and his knowledge are always welcome...and always right on target .What are your creds? Besides being insulting and demeaning, that is.

By the way...I neg-repped your post. You earned it.

You did notice the 2 capitals in the sig BS lol

 

[trimmmed]

The man isn't a retard at all. He's probably helped more people on AS than any other single member. His advice and his knowledge are always welcome...and always right on target .What are your creds? Besides being insulting and demeaning, that is.

By the way...I neg-repped your post. You earned it.

Hey bob, we are not much for negging newbies around here... however i followed your lead

Now who do you suppose this guy is? (again) He seems kinda fixated doesn't he?

And to Ian..........don't blink again, lol

 

[Gologit]

You did notice the 2 capitals in the sig BS lol

No...I hadn't noticed...and thank ye kindly for pointing it out. Appropriate, no?

I wonder who he really is. Maybe he can give us clue...if he has the balls.

 

[Gologit]

Hey bob, we are not much for negging newbies around here... however i followed your lead

Now who do you suppose this guy is? (again) He seems kinda fixated doesn't he?

And to Ian..........don't blink again, lol

LOL...I only neg those, newbies or not, who stand right up and ask for it. You know the kind I mean...they go around wearing targets made out of their own words.

But I promise to keep it to the truly deserving.

 

[drmiller100]

Not easy as it's not positive displacement, but a fans like a pump and every vane type pump has a pump curve with an optimum speed for efficiency. If a motor was hopped up 10% in RPM over stock I would not expect to get 10% more air flow from the cooling fan but don't imagine it would be too much less than the 10% gain in RPM.

.

centrifical fans are exponential. rev it up 10 percent, and you will see a fair amount more then 10 percent air.

 

[Tzed250]

centrifical fans are exponential. rev it up 10 percent, and you will see a fair amount more then 10 percent air.

Until cavitation sets in...

 

[Taxmantoo]

You did notice the 2 capitals in the sig BS lol

And he's from Hawaii, and oh so polite. Must be Barack-Senator.

 

[timberwolf]

Takes four times the energy to turn a fan twice as fast, but it does not move four times the amount of air. So don't think you can say the output is exponential in terms of air volume. Real world turned twice as fast it moves twice the air minus the increased losses encountered in short circuiting around the fins. Don't think a fan in air can truely go into cavitation, but the faster it's driven the less efficient it becomes to the point where turning it faster results in no additional output.

 

[Taxmantoo]

I believe that your combustion temps at the time of combustion are not going to change much if any.

EGR is used in road going four strokes (I know, apples and oranges) to reduce formation of oxides of nitrogen by reducing combustion temps. Retarding the timing has a similar effect (and both reduce efficiency). In order to eliminate unburned intake charge from going out the exhaust, you have to accept poor scavenging, which is similar to EGR, in a pollution controlled saw. Flame temps go down, but OTOH, you're holding hot exhaust gases in your cylinder, lessening the cooling effect of the fresh intake charge. Like Lake said, too many variables to just reason it out in your head.

 

[24d]

On airboat props, we consider cavitation as when the tips break the speed of sound, also they work best at the rpm they were designed for. I'd be willing to bet all fans work basicly the same way.

 

[timberwolf]

WIKI deffinition

Cavitation is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure.

Basically it's boiling the liquid and creating gas bubbles that destroy the efficient shape of the impeller or propeller.

 

[Tzed250]

On airboat props, we consider cavitation as when the tips break the speed of sound, also they work best at the rpm they were designed for. I'd be willing to bet all fans work basicly the same way.

Yes, when a part of the fan breaks the sound barrier the laminar flow stops. This is the limit for propeller driven aircraft.

Of course, for the circumference of a 100mm flywheel to go Mach 1, it would need to turn nearly 63,000RPM...

 

[husq2100]

doesnt your saw turn 63,000rpm

my muffler modded 346xpne does and thats tuned rich for break in. of coarse im running 32-1

Serg