Muffler placement, does it matter?

jimboburgess

jimboburgess

it's a hondamatic
A general question to get the discussion going.

How much does it affect the powerband to have the muffler at the end of the exhaust versus closer to the headers.

Back when i was working on cars, (tuner cars) I always like to put the muffler right after the cat to get a deeper engine sound. I'm thinking about doing something like this on my bike. i.e. header>muffler>maybe another 12"-18" of pipe. Once i do it i can see what having the extra pipe on there does. but for now I wish to speculate about it.

Thoughts?
 
effect it tons..... a muffler "gets bigger" so with in the 1st couple hundred RPM, it can build a wall of CONSTANT pressure. Called back pressure .With out proper back pressure, power is lost..... no matter how ya cut it.
 
It all depends. Put the muffler close to the headers kills power and torque but probably sounds "powerful". Exhausts should be properly designed to extract power.
 
what are examples of "properly designed" exhausts? how do you strike a good balance between back pressure/and flow?
 
jimboburgess said:
what are examples of "properly designed" exhausts? how do you strike a good balance between back pressure/and flow?
Click to expand...

yer stock one. Or something from Apolo Cone. I would say they are good examples.
 
It does also depend entirely on the engine configuration.

For a 2 stroke, the back pressure and the amount of back pressure is critical for the engine to work correctly, on a 4 stroke, back pressure is less important, the valves do an extremely good job of sealing the cylinder.

HOWEVER, the exhaust makes only a little difference on a single cylinder bike, but if you had multiple cylinders and had primary and secondary headers, 2 into 1 or 4 into 2 into 1 etc. How you tie these together, can improve performance, you can use the vacuum created from 1 cylinder to pull more air through the next during the valve overlap, when I get home I will try and dig out some of the equations for calculating exhaust gas flow and optimum exhaust dimensions.

As my current cafe racer build is only a small single 4 stroke, I plan to have a play with silencer position, and exhaust length and compare torque and power curves on the dyno, to see what happens
 
phildawson8270 said:
..................................
As my current cafe racer build is only a small single 4 stroke, I plan to have a play with silencer position, and exhaust length and compare torque and power curves on the dyno, to see what happens
Click to expand...

Can't wait to see those test results
 
Grab a copy of A Graham Bell, Performance Tuning for Four Strokes

http://books.google.com/books/about/Four_Stroke_Performance_Tuning.html?id=OTOYHRSX_XcC
 
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