GUIDE: How does a tuned pipe work?

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Nitroaddict

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" Tuned Pipes - Or how the Resonance Effect is affecting Performance" Courtesy of www.twf8.ws

We all know that the exhaust pipe and the length of the manifold have an effect on our engine's power output, but how exactly does it work?
--------------------------------------------------------------------------------
First, imagine an engine with all ports, like the one below:

ztakt.gif


In our two-stroke engines, the intake port and the exhaust
port are open at the same time. This means that the amount
of fresh mixture that will be trapped in the combustion
chamber is limited. An engine produces the more power the
more fuel (together with air) detonates.

Thus, our goal is to increase theamount of fresh mixture burnt during each cycle. To do so, we need something that prevents the fresh mixture from leaving the combustion chamber unburnt.

Have a look at the animation below.

2t_fase.gif


You see that the burnt exhaust gases form a pressure wave
which goes to the end of the pipe (or the baffle), then the pressure wave reverses direction and prevents the fresh
mixture from leaving the combustion chamber. That is the back pressure.

So, knowing all this, how can I improve my buggy engine's performance?

What you can do to tune the exhaust system to your liking is to change the length of the exhaust (distance from engine's exhaust port to pipe's baffle). You can normally tune that by adjusting the length of the coupler (connecting tube between manifold and pipe). Making it longer means that the pressure
wave takes longer to come back. Thus, it gives best performance at low RPM, say, you get more bottom end, acceleration. Having a shorter exhaust means that the pressure wave is back faster, so you have the resonance effect in the high RPM band. Thus, you get more top speed.


Have fun racing, bashing, or just wrenching!
 
Last edited:
doesn't the shape or thickness of the pipe have an effect as well? Or is it only the length? (no pervetedness intended)
 
That is correct, rob, but i was just showing them how to adjust the current pipe they have, rather than purchasing a new one.

A general rule of thumb:

the greater the angle between the fattest part and thinnest parts of a pipe, the greater the torque aid.

The smaller the angle, the greater the RPM aid.
 

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