How do pipes work?

[mcgrail.s]

I understand whats inside them, I know that their main job is to use the sound wave generated by the engine to pull the spent gas out of the chamber, but what else do they do other than reducing noise?

What is the benefit of having one pipe per cylinder rather than just having a manifold connecting all three cylinders to one pipe?

 

[LEE]

check here

There are plenty of websites on exhaust theory.
Here is some good info for you to understand the design changes over the years.
http://www.motorcycle.com/how-to/ho...ambers-work-and-why-you-should-care-3423.html

 

[EricW]

I've wondered the same. To go one further, how much does the design/function of a pipe on a naturally aspirated motor change or become a non-issue once you've added boost? And to go two further, is the effect of boost on pipe design/function different between 2 and 4 strokes? What would happen if you ran a straight pipe on either without the expansion/reduction component?

Prolly dumb questions, but these are the things I wonder when I gaze off into space (usually like at times when wifey is explaining why one carpet style/design is better than another or what clothes you never wash together). These are questions for another day.

Good post, hope the tuning guru's chime in. EW

 

[mountainbigbull]

Without getting wordy (like the link above) on a two stoke the pipe creates a certain amount of back
pressure that acts almost like exhaust valves in a four stroke. So the correct amount of back pressure is important for good performance. This is the reason for after market companies that make a pipe to increase performance. After market may for example create better top hp but change lower end performance. OEM's create a balance on overall performance. Kinda like street vs. racing.
On 4 stroke less back pressure is desirable. So less restricted exhaust is wanted due to the design of a 4 stroke exhaust valve. Turbo's on four stoke create back pressure this is why you hear of needing stiffer exhaust springs to help close the valve's (not sure if there are needed on the Yamaha engines Yamaha guys can help me out here)

 

[Motley Doo]

^^This is also why a pipe can be built to make horsepower at certain RPM ranges. The length and shape of the pipe makes the pressure wave inside take longer or shorter times to get back to the cylinder, in doing this, you drop horsepower in some areas and gain hp in others, this is why the powerband is made.(of course powerband is also affected by timing, port timing, porting, etc...)

Now, someone else can answer this for me, 2 stroke boat motors don't have an expansion chamber, some older 2 stroke street bikes didn't, and my buddies Kit Fox airplane that is running a 583 rotax motor doesn't either. Aren't you loosing rediculous amounts of hp and efficiency by pushing that unburned fuel out the exhaust?

This should be cool post to watch to see what the experts have to say!

 

[MPS]

Without getting wordy (like the link above) on a two stoke the pipe creates a certain amount of back
pressure that acts almost like exhaust valves in a four stroke. So the correct amount of back pressure is important for good performance. This is the reason for after market companies that make a pipe to increase performance. After market may for example create better top hp but change lower end performance. OEM's create a balance on overall performance. Kinda like street vs. racing.
On 4 stroke less back pressure is desirable. So less restricted exhaust is wanted due to the design of a 4 stroke exhaust valve. Turbo's on four stoke create back pressure this is why you hear of needing stiffer exhaust springs to help close the valve's (not sure if there are needed on the Yamaha engines Yamaha guys can help me out here)

good thread....mountainbigbull described my understanding

 

[LEE]

Motley Doo, straight pipes on a two stroke will work as on old bikes and boats but you lose efficiency as it will only run good at a given constant speed. You will have more efficiency with a correctly piped sled for your engine, altitude, riding style with expansion chambers & can or stingers.