Tuned Pipes . . . Discussion and Information 


Topic:                         This article is aimed at capturing all of the things needed to understand how tuned pipes work - and - if one can be built for a wetbike.


The RUB:                     The upper cylinder's length from the port opening to the base of the motor is EXTREMELY LONG compared to the lower cylinder. That is, the upper one is 216mm and the lower is 34.7. Most software packages calculate that the length of this port + the length of the first segment of the tuned pipe (B1+B2 below) should be around 156mm - thus - the upper port is TOO LONG right outtta da gate. (see illustration below)


In A Nutshell:                Unless you know how to "shorten" the upper port by about 55 or so millimeters, the ultimate single tuned-pipe setup cannot be built. That is, a tuned pipe that works for both cylinders cannot be built.


What to do?                  If it was me, I'd build a pipe that works for the lower cylinder the best (ie. tuned for the lower cylinder) and hope for the best. To make that work like it should, some type of diverter would need to be built in the motorplate exhaust area so that majority of the returning exhaust wave wouldn't go to the upper cylinder (following the outside wall of the exhaust. If you were looking at a motorplate (with engine removed), cup your hand and slide it down through the opening - that's the type of air-foil thing-a-ma-jig I think would need to be put in there.


What did WPS do?          I dunno but . . . I can take an old leaky WPS pipe and cut it open on the bandsaw. Then we could measure it and find out what the dimensions of the cones are. Stay tuned . . . 


Port Length                                     Upper Cylinder         Lower Cylinder

  • Piston to Pipe Length                    216.0                   34.7
  • Width at Port Opening                     50.0                   50.0
  • Effective Height at Port Opening      30.1                   30.1

 

 

 

09/11/2017

Copyright 2012 Capt'n Obveeus

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