Nat Puffer wrote:

Paul,
Thank you for the excerps on determining the optimum length for a tuned
exhaust system. One of my cylinders runs lean, and I think the cause is too
short a pipe. I cannot lengthen it by much because of space limitations
within my cowling. Another builder who has raced with 2 cycle engines has
suggested that reducing the diameter of the pipe has the same effect as
lengthening the original pipe. Your reference doesn't say anything about
pipe diameter, or the number of bends. Can you tell me whether making the
diameter smaller and increasing the number of bends will have the same
effect as increasing the length?
Regards,
Nat

There is some data in that Advanced Engine Technology book that suggest the
tunning can be changed slightly by changing the diameter of the pipe.

If you have a carb on there Nat it might just be a mixture distribution
problem common with carb manifolds. A small amount of carb heat might
help as would a slight amount of throttle closing. That gives a bit
more  mixing turbulence in a carb manifold. Also a worn lobe on the 
camshaft can have some strange effects on the EGT.

I know Dave Anders spent a lot of time and money tuning his mechanical 
injectors so all EGT's were within ten degrees of each other.

Paul Lamar
 
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