Cyrille -
I'm running dual SUs on my 1500 (removed from a Midget 1500 sitting in an 
English "Breaker's Yard"), a PaceSetter 4-into-1 manifold, but an otherwise 
pretty stock engine.  Afer some experimentation, I settled on a 1 3/4" 
system running a low-restriction muffler.  
At 2" the "seat of the pants dynamometer" told me that I was losing some low 
RPM torque (off the line aceleration suffered).  At 1 1/2" it seemed to run 
out of breathing ability at the top-end.  It was all subjective, but 1 3/4" 
seems to be the driveability "sweet spot" at least for my driving style and 
conditions.
The Weber set-up may make a difference, but I don't imagine that it will be 
huge.  Anyway, I hope that helps...
Chris K.
On Wed, 15 Feb 2006 10:40:59 -0700, de Brebisson, Cyrille (Calculator 
Division) wrote
> Hello,
> 
> I am looking for help on setting up my exhaust system for my 1500cc
> midget.
> 
> I have weber carbs (downdraft) and 4 -> exhaust system, but I need to
> find what diameter to use for the rest of the system (no cat 
> converter).
> 
> Any suggestions?
> 
> cyrille
 
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