Chainsaw Pipe Exhaust theory

[edisto]

General theory question that might apply to “dog dick” style pipes:

If the ideal distance of an expansion pipe is 40cm, can a 20cm pipe utilize the sound wave on its secondary reflected pulse? What about 10cm?

Both waves (the initial negative and subsequent positive) have to occur during one exhaust port open cycle to be beneficial.

Related question:

What negative effects does the sound wave have if it hits the exhaust port too early in the cycle?

The initial negative wave pulls charge into the exhaust (helps scavenging), and the subsequent positive wave stuffs some of that charge back into the cylinder (supercharging). Early arrival of the positive wave would interfere with scavenging.

 

[Fabulous]

Just so you know...the long pipe is the first step in an expansion chamber. The pulse leaving the opening reflects a negative pressure wave that helps with scavenging. A straight pipe works at only a narrow range of rpms. A cone reduces the strength of the pulse, but spreads it over a wider range of rpms.

Having seen the length of the pipe required, it should be obvious to you that the "dog dicks" are not tuned pipes.

Not “tuned” as in an expansion chamber however anything you do to get the exhaust out (“can’t get in if it can’t get out”) quicker is going to increase performance. If one were to “pipe” a stock muffler one could make the argument that the torque curve (and thus hp) will vary depending on the size / length / number of the outlet tube(s) and numbers of tubes. It’s common knowledge that a 3/4 inch tube placed “x” distance into the muffler will give enhanced performance on an “x” cc saw. In fact , hay chaff and sawdust has uploaded several videos where he shows , plain as day, this effect … and yes , he has a Dyno to show “real world results”. I suggest perusing his collection - you might just learn something! As for me, saws are tested in the wood and I can unequivocally say that a “dog dick” muffler will outperform any stock can everyday of the week and twice on Sunday

 

[edisto]

Not “tuned” as in an expansion chamber however anything you do to get the exhaust out (“can’t get in if it can’t get out”) quicker is going to increase performance.

Like a simple widening of the outlet?

It’s common knowledge that a 3/4 inch tube placed “x” distance into the muffler will give enhanced performance on an “x” cc saw.

3/4" seems oddly specific. How did you arrive that number? Or are you just parroting the YouTube? Can you solve for x?

What is common knowledge is that opening up the outlet of a box muffler improves performance. At some point the loss of back-pressure will negatively affect performance, but modern muffler designs attempt to keep charge out of the exhaust, sacrificing performance for emissions.

I suggest perusing his collection - you might just learn something!

You have been perusing his collection a lot, and seem to have come away with very little.

Check out his video where he compares modifications to box mufflers on a Holzfforma G366:



Orange is stock, green is his modification, and the others were modified mufflers sent to him:


Now, compare those gains to the gain from his magical "Ironhorse" on a Husky 455 (pay attention to the scale on the Y-axis):




3 hp to 3.4 hp with the iron horse (13%), similar to the single opening mods on the box mufflers, and less than the double-opening mod by a lot.

No-one is saying that a "dog dick" wouldn't outperform a stock muffler, just that you could get similar results in a fraction of the time with a stock muffler and a step drill bit.

 

[Fabulous]

What also sucks about dog dicks is that they are super loud. They just won’t shut up.

Unfortunately they ARE considerably louder than a stock muffler or a stock muffler with another outlet affixed but that’s the price you have to pay for increased performance

 

[Fabulous]

Like a simple widening of the outlet?



3/4" seems oddly specific. How did you arrive that number? Or are you just parroting the YouTube? Can you solve for x?

What is common knowledge is that opening up the outlet of a box muffler improves performance. At some point the loss of back-pressure will negatively affect performance, but modern muffler designs attempt to keep charge out of the exhaust, sacrificing performance for emissions.



You have been perusing his collection a lot, and seem to have come away with very little.

Check out his video where he compares modifications to box mufflers on a Holzfforma G366:

View attachment 476259

Orange is stock, green is his modification, and the others were modified mufflers sent to him:
View attachment 476260

Now, compare those gains to the gain from his magical "Ironhorse" on a Husky 455 (pay attention to the scale on the Y-axis):

View attachment 476261


3 hp to 3.4 hp with the iron horse (13%), similar to the single opening mods on the box mufflers, and less than the double-opening mod by a lot.

No-one is saying that a "dog dick" wouldn't outperform a stock muffler, just that you could get similar results in a fraction of the time with a stock muffler and a step drill bit.

The ironhorse pipe is single outlet guy. A properly designed, dual - outlet pipe will outperform any can muffler deflector configuration you can possibly make … and that’s not an opinion - it’s a fact! I mean cmon … it’s called a muffler for a reason … it muffles the sound ! It’s not designed for performance and simply adding on a deflector on the other side is most certainly NOT going to outperform a dual outlet pipe! You can argue this until you are blue in the face but you would be proven incorrect , not only by me but most likely the 10,000 other people who have actually DONE the work … IF you don’t believe me than take the can muffler completely off the saw and make a few cuts …. Zero back pressure - loud as hell ….. proven to cut faster …. Period

 

[edisto]

that’s not an opinion - it’s a fact!

Your inability to distinguish between the two seems to be causing you a number of issues.

 

[Fabulous]

The ironhorse pipe is single outlet guy. A properly designed, dual - outlet pipe will outperform any can muffler deflector configuration you can possibly make … and that’s not an opinion - it’s a fact! I mean cmon … it’s called a muffler for a reason … it muffles the sound ! It’s not designed for performance and simply adding on a deflector on the other side is most certainly NOT going to outperform a dual outlet pipe! You can argue this until you are blue in the face but you would be proven incorrect , not only by me but most likely 10000 other people who have actually DONE the wo

That’s the reason he’s been banned from here under different usernames multiple times lol. He only understands what he wants to understand. Cat dicks and dog dicks are all the same, just a little smaller

With all due respect…. I’ve perused your utube channel and I do not see anythingshowing YOU testing any pipes or mufflers or any instructional/educational material at all … tho I may have missed something. All I see is a guy cutting wood cookies in his backyard with so and so’s ported saw. Which is fine IF that’s what you want to do. For the rest of us, who don’t know everything about everything already , we shall continue our collective education unabated

 

[huskihl]

With all due respect…. I’ve perused your utube channel and I do not see anythingshowing YOU testing any pipes or mufflers or any instructional/educational material at all … tho I may have missed something. All I see is a guy cutting wood cookies in his backyard with so and so’s ported saw. Which is fine IF that’s what you want to do. For the rest of us, who don’t know everything about everything already , we shall continue our collective education unabated

Yeah, sorry not sorry if I don’t show everything I do on video lol

 

[Fabulous]

Yeah, sorry not sorry if I don’t show everything I do on video lol

That’s fine ! Just respect the folks who do! There’s a lot of guys/gals with good info out there - best served continuing to learn vs maybe thinking we know everything already. If you don’t agree with someone’s opinion then don’t agree or try and kindly offer your point of view , maybe BOTH parties learn something right? - that’s what MEN do right ?

 

[59billy]

That’s the reason he’s been banned from here under different usernames multiple times lol. He only understands what he wants to understand. Cat dicks and dog dicks are all the same, just a little smaller

Ah, there's backstory I don't know about here!

@59billy I've had about enough, and I don't think I'm alone.

You're not alone. At this point, I hope everybody can put away their dicks of whatever species and return to useful discussion.

 

[Cyrille72FR]

Both waves (the initial negative and subsequent positive) have to occur during one exhaust port open cycle to be beneficial.

The initial negative wave pulls charge into the exhaust (helps scavenging), and the subsequent positive wave stuffs some of that charge back into the cylinder (supercharging). Early arrival of the positive wave would interfere with scavenging.

That is the ideal "tuned" exhaust.

But as I said it require some dimensions, we cannot use in work saw.
Some do in competition chainsaw, Dyno Joe measured some with impressive gain, which is perfectly in accordance with physics theory.

Muffler are mainly a sound dampener, working as a expansion chamber : lowering gas pressure, and lowering speed, plus a low pass filter if a tube is present working as a bass-reflex, filtering out some of the mid-frequencies noise.
I measured this effect on my MS261 exhaust.

When we increase the port size, we increase it's flow capacity, but we reduce its muffler effectiveness ass we increase the low-pass frequency.
Or we could increase diameter and the length together to keep the damping effect.

Hay chaff and sawdust shown us that there is a specific dimension of can volume and tube dimensions which offer the best performance.
I will copy is results on my 026 can, and measure what I can.
I suspect there is something about the acoustic behavior of the exhaust muffler : band-pass, and/or gain... even if it doesn't match the performance of a true exhaust port.

 

[huskihl]

That’s fine ! Just respect the folks who do! There’s a lot of guys/gals with good info out there - best served continuing to learn vs maybe thinking we know everything already. If you don’t agree with someone’s opinion then don’t agree or try and kindly offer your point of view , maybe BOTH parties learn something right? - that’s what MEN do right ?

Like I said earlier, it’s not an opinion. I’ve done lots of my own testing and seen the dyno charts from others.

But even to someone who hasn’t seen any of that testing, it doesn’t take a rocket surgeon to see and hear that the pot metal pony style pipes make a saw high strung and lose torque

 

[Fabulous]

Like I said earlier, it’s not an opinion. I’ve done lots of my own testing and seen the dyno charts from others.

But even to someone who hasn’t seen any of that testing, it doesn’t take a rocket surgeon to see and hear that the pot metal pony style pipes make a saw high strung and lose torque

That’s not been the general consensus among folk who use them - Like I said : hay chaff and sawdust has videos showing the Ironhorse pipes on his Dyno - believe it or do not believe it - it really doesn’t matter to me

 

[bwalker]

That’s not been the general consensus among folk who use them - Like I said : hay chaff and sawdust has videos showing the Ironhorse pipes on his Dyno - believe it or do not believe it - it really doesn’t matter to me

I have seen dyno results for motors that look awesome but suck in real life. The dyno is a tool that gives one some indication of performance, but ita not the last word by any means.

I've done alot of testing with mufflers. When the exhaust opening increases you make more power at the expense of "stump torque". At some point. This happens with both a modified stock outlet or a Bark Box/ Straight Shot.
The contraptions guys are selling these days have no theory behind them other than increasing the outlet size increases HP on a dyno and thats most certainly the truth. Its also true that as the HP goes up stump torque falls off.
Plus the contraptions look ridiculous and are obnoxiously loud. No thanks.

 

[SawAddictedFarmer]

I have seen dyno results for motors that look awesome but suck in real life. The dyno is a tool that gives one some indication of performance, but ita not the last word by any means.

I've done alot of testing with mufflers. When the exhaust opening increases you make more power at the expense of "stump torque". At some point. This happens with both a modified stock outlet or a Bark Box/ Straight Shot.
The contraptions guys are selling these days have no theory behind them other than increasing the outlet size increases HP on a dyno and thats most certainly the truth. Its also true that as the HP goes up stump torque falls off.
Plus the contraptions look ridiculous and are obnoxiously loud. No thanks.

How much of the tourqe can be brought back with a timing advance?
I'm still pretty new at all this so just asking a question .

 

[bwalker]

How much of the tourqe can be brought back with a timing advance?
I'm still pretty new at all this so just asking a question .

I have no idea, but would guess that it depends on the saw.
I do know that the MS260 I did testing with was already advanced before I started and the loss of torque was still apparent.

 

[Ketchup]

How much of the tourqe can be brought back with a timing advance?
I'm still pretty new at all this so just asking a question .

Interesting question. I don’t think there’s a direct correlation, but getting the ignition right for your RPM is important. More RPM usually means more Torque.

Thread 'Part Five: Ignition Timing'

May 5, 2017

We've covered the exhaust port.

http://opeforum.com/threads/part-one-the-exhaust-port.7279/

The intake port.

http://opeforum.com/threads/part-two-the-intake-port.7290/

And the transfer ports.

http://opeforum.com/threads/part-three-the-transfer-ports.7306/

And compression.

http://opeforum.com/threads/part-four-compression.7318/

So now let's talk about ignition timing.

Should we advance the timing?

How much?

How can we tell if it's too far advanced?

Will timing advance make the engine overheat?

Can too much advance cause the engine to run lean...

• Mastermind
• Replies: 296
• Forum: Chainsaws

• 

 

[SawAddictedFarmer]

Interesting question. I don’t think there’s a direct correlation, but getting the ignition right for your RPM is important. More RPM usually means more Torque.

Thread 'Part Five: Ignition Timing'

May 5, 2017

We've covered the exhaust port.

http://opeforum.com/threads/part-one-the-exhaust-port.7279/

The intake port.

http://opeforum.com/threads/part-two-the-intake-port.7290/

And the transfer ports.

http://opeforum.com/threads/part-three-the-transfer-ports.7306/

And compression.

http://opeforum.com/threads/part-four-compression.7318/

So now let's talk about ignition timing.

Should we advance the timing?

How much?

How can we tell if it's too far advanced?

Will timing advance make the engine overheat?

Can too much advance cause the engine to run lean...

• Mastermind
• Replies: 296
• Forum: Chainsaws

• 

Thanks! I hadn't seen that yet.

 

[Ketchup]

Thanks! I hadn't seen that yet.

The second sticky in the chainsaw forum is a treasure trove. Buckle up for some reading time though!

 

[Ketchup]

I have seen dyno results for motors that look awesome but suck in real life. The dyno is a tool that gives one some indication of performance, but ita not the last word by any means.

I've done alot of testing with mufflers. When the exhaust opening increases you make more power at the expense of "stump torque". At some point. This happens with both a modified stock outlet or a Bark Box/ Straight Shot.
The contraptions guys are selling these days have no theory behind them other than increasing the outlet size increases HP on a dyno and thats most certainly the truth. Its also true that as the HP goes up stump torque falls off.
Plus the contraptions look ridiculous and are obnoxiously loud. No thanks.

Well said.
But I don’t want to completely discount a muffler design just because idiots like it. I think there’s something to a flat wall across from the exhaust port and to reduced muffler volume. Even idiots have happy accidents or get something partially right.