Intake runner sizing..

[Graydon D. Stuckey]

On Wed, 21 Feb 1996, Craig Pugsley wrote:

> I have a Mazda 13B street port that I am planning to EFI, and am
> wondering about intake runner length/diameter characteristics for max
> torque/max power.
...
> Is it true that the longer a runner the lower in RPM the torque peak
> will be? If that's the case should the primarys be long and the
> secondarys short?

That is basically true.  If you are using the secondary control valves, 
then, yes you could tune the secondaries for high rpm use (3500 and up) 
and tune the primaries for low rpm use (less than 3500 rpm).

	Personally, I think those 6-port valves are more restrictive than 
they are worth.  I would take them out, and fab up variable length intake 
runners.  Then you can tune all the runners for all rpm ranges.

Later,								
Graydon D. Stuckey								
graydon at apollo.gmi.edu								
Flint, Michigan   USA
'86 Audi 5000 CS Turbo Quattro, GDS Racing Stage II				
'85 Mazda RX7 GS 12A-leaning-towards-a-13B-soon