Skip the muffler all together

[sachsmo]

Random pic from the web;

Guess he never thought of putting a bar and chain on eh?

Motorheads will be motorheads!

 

[Chris-PA]

You don't need low pressure when the exhaust opens. There is plenty of pressure in the cylinder.

The opening of the exhaust creates a positive pressure wave. When a wave in a tube leaves that tube, a wave of the opposite sign travels in the opposite direction. This negative pressure wave needs to get to the exhaust port once the big pressure differential is gone to help "pull" more exhaust out, and more charge in to the cylinder.

The wave from an abrupt opening would be strong, but too short in duration. An expanding cone produces the same effect as an abrupt opening, but with less strength and more duration. That is what the first cone in a tuned exhaust is for.

When a pressure wave moving though a pipe hits the closed end of a pipe, a pressure wave of the same sign is reflected back. Again, a cone (in this case constricting) produces the same effect, but with less strength and longer duration. This is what the second cone is for. The reflected positive pressure wave produced by the second cone "chases" the negative wave towards the exhaust port, stuffing back some of the charge that was "pulled" out of the cylinder by the negative pressure wave.

All of this has to happen between the opening of the exhaust port and the closing of the exhaust port.

Check out the gif in post #20 of this thread.

Thanks for the explanation - I understand now what you are saying, and while it is counter to how I understood it to work I will do some more reading on it as I get the chance. I always appreciate the opportunity to have a good discussion about how things work without people getting upset!

 

[edisto]

Thanks for the explanation - I understand now what you are saying, and while it is counter to how I understood it to work I will do some more reading on it as I get the chance. I always appreciate the opportunity to have a good discussion about how things work without people getting upset!

There is a link to Jennings' book in post 37. He describes his design, and many of the considerations. If it is the site I'm thinking of, there also are links to pdf articles, including one he wrote on testing his expansion chamber design.

If not, just do a search for "Jennings pdf".