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Re: tuned lengh headers for a a14. |
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Home away from home  
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2002/5/1 12:48
From Millgrove Vic OZ
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The formula for a tuned length pipe is P=((850*ED)/rpm) -3 where ED is the degrees before bottom dead centre that the exhaust valve opens plus 180 degrees. (ref 4 stroke performance tuning by A Graham Bell pp112)
From the figures I have, with a cam opening 57 degrees BBDC the tuned length pipe for 4 into ones would be between 27.7 to 28.4 inches if the pipe was designed to work between maximum torque and maximum HP engine speed at say 6500 rpm.
For an interference system the primaries would be 16.5" in length and the secondaries 27.7 - 16.5 = 11.2" in length.
The pipe ID for the primaries is calculated from (((sqr root((cc per cylinder/(tuned length + 3) *25))) *2.1 that turns out to be 1.434" ID so an 1 5/8" primary would be best.
The secondary pipe diameter is ((sqr root(ID*ID *2)) * 0.93. This works out to be 1.886" ID for the secondaries, so 2" OD pipes are the go.
Hope this helps.
Posted on: 2004/3/30 0:14
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