Miata Mailing List: November 1999, Message #150

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In a message dated 11/4/99 12:59:27 AM Eastern Standard Time, 
fletch@powerlink.co.nz writes:

<< Most sources suggest 4 into 1 is good for top end power, and 4-2-1 is 
better
 for midrange torque.
  >>

* Fletch,

My understanding is that your view is correct. We have pondered this a long 
time in the motorcycle racing world..and this is what our data shows...4 into 
1 usually increases top end, but also yields a flat spot in the 
middle...while the 4-2-1 decreases top end but cleans up the middle...the 
solution (in the motorcycling world) is to put a exhaust valve that opens and 
partitially closes the header system, making it both a 4-1 and a 4-2-1 when 
the rpm's and power is needed...

FWIW,

Aaron
aaron@miata.net