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Date: Wed, 01 Jun 2005 18:01:41 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Combining ports on 6-port
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Found the answer to the question I had the other day.  On a 6-port, why 
not just combine the two runners in the side housing?

From  http://www.mazdatrix.com/faq/port6p.htm

"If the separate ports (in the end housings) are simply made into one 
large port, the bottom and mid-range torque suffer a lot, and the port 
velocity is compromised as the intake flows from the manifold into the 
intake runner. The intake port timing of this configuration is: later on 
opening than a peripheral port, but roughly equal to intake closing on a 
peripheral port! That's a LOT of timing and port volume for a street car."


Bottom and mid-range torque are all but meaningless to us as long as 
it'll idle.  Right? 

The port velocity will only be compromised if you were using the stock 
intake that.  I don't know of any airplane builders doing that.  If 
you're building your own anyway, you'd make the runner big enough so 
there isn't an upstream obstruction and maintain the velocity throughout.

It seems to me that joining the outside runners on a 6-port is an 
excellent idea for an airplane application.  Somebody set me straight 
before I do something stupid.

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