Tuned Pipes for Chainsaws

Tig welding is what I'm going to be doing for muffler mods from now on.

 

Have done some with copper, it is actually harder to do because IME it acts like a heat sink and I had trouble getting the metal of the muffler to stay hot enough for the 50N to flow.

 

The numbers said that .500 was the correct for engine displacement and muffler volume after all the interor obstructions and the pipe were subtracted. The length of the pipe needs to be between 3.75 and 4.25 inches in length. The smaller diameter pipe you use the shorter the pipe needed. Did not want to use .375 because it looked stupid on a 372.

 

Here I would have thought a smaller pipe would need to be longer

 

Hello all I am Zach, I can shed some light on the scavenging effect mentioned earlier by KRL. First off I would like to say that KRL's knowledge of the two cycle engine is very respectable. I race two cycle gokarts for a very reputable engine builder known nation wide. What happens when the exhaust scavenges is far different in a two cycle compared to a four cycle. Two cycle scavenging is when the exhaust gases being forced out by the piston, bounce off of a wall or convergence in its path, and create what we call a pulse. When the gas pulses, it forces uncycled NEW charge air, that has escaped the cylinder via the exhaust port as a product of the transfer stroke's, downward piston movement creating an excess of crank case pressure, leading to the escaped charge air, back into the cylinder. Thus allowing for a more efficient and stronger burn, during power stroke. With a "box muffler" this happens in a very erratic and uncontrolled fashion, and is less efficient than that of the tuned pipe and furthermore, the expansion chamber. The tuned pipe was some of the very first technology advancement in the two cycle industry. What the tuned pipe does is it allows only a certain determined amount of gases out of the cylinder before the piston closes the exhaust port. Being that this pipe is smooth and un restrictive in its velocity pressure allowance, the pulse is more controlled and less erratic, but the fact remains of its limited diameter that still keeps the static pressure up creating a yet very weak, but still functional, pulse. When the tuned pipe is mated to an "expansion chamber" or conical convergence then mated to a conical divergence leading to the tuned header (explained moving from final gas exit back to cylinder), creates an extremely well controlled pulse and using a lot of math, can create a peak HP and TQ number, at any point during the "power band" or time at which the engine runs most efficient.

If anyone would like anymore light shed on scavenging in two or four cycle engines, feel free to PM me!

P.S. I cannot stress my respect for anyone who has posted prior, I am only here to help!

 

Welcome to the club

 

I saw this thread new and thought KRL was back. It took me to the first lost..guess I had never clicked it before.?

Good in for IAsaw!

 

Heck of a first post!

 

Given what transpired, I do not see him resurfacing.

 

I just reviewed this thread for the first time. Setting my engineering degree aside, 95% of the people will likely benefit more from learning how to sharpen a chain and maintain it than add the tunes. With a tuned saw and a new chain, you will throw some chips for sure. Having been around many people using chainsaws, many do not sharpen them correctly so the idea of tuning seems like a waste and potential for disaster. By no means do I have anything against tuning, since if done right it can create results. I am just happy to be in the woods and blocking trees up, which is what I did all day yesterday!!!

 

I have studied tuned pipes and know the theory on how they work. Why, because I was curious and wanted to know how they worked. That does not mean I am going to go out and build one. There are probably other people here that are just as curious and would like to know for the same reasons. So if an individual wants to come on here and explain it all out then I believe there are curious members here who will enjoy reading and understanding it.

 

Magcraft, I agree and understand. Just wanTed to throw out my opinion and caution since it takes some work and knowledge to capitalize on this effort.

 

I agree it does take a lot of work and time if your going to do it right and have it tuned for just the right RPM.
Unlike dirt bikes chain saws are always ran at WOT and so that is where you want the peak power.

 

Personally I am a Stihl man, I own an 026, ms260 and one echo cs400.

I can agree with WNW, the most important part of the saw is chain.

I was laying in bed last night and happen to come across this thread, while continuing my research into how many people are building "hot saws" and what they are doing for tuning in their saws. I figured I could share my knowledge of the two cycle engine as I saw some asking on scavenging.

Like I said, please PM me for more in depth info on two cycles!