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Old 02-17-2017, 10:45 AM
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Originally Posted by flybyjohn View Post
Does the length you are referring to mean the length from the end of the pipe to the back of the can or the length from the exhaust port to the back of the can?

When I speak of the length of the system, I mean the overall length from the exhaust port to the end of the convergent cone of the pipe (in regard to a regular tuned pipe). For a mousse can pipe, your effective length is from the exhaust port (more technically the glow plug since that's where combustion starts) to the back of the can. The further the header protrudes into the can the shorter the effective length becomes, so moving the can in and out from the header will change the length of the system this changing the tuning of the system. If your pressure wave comes back too soon (pipe too short), you can end up with the engine running hotter and losing power because it's pushing exhaust gasses back into the combustion chamber. If the pressure wave comes back late, it will still be down on power but it just won't be pushing the full fresh charge back into the combustion chamber. In essence it's better to have the system a little too long than a little too short. Of course if the system is too short, running a little less prop load (more rpm) will get the engine on the pipe.