Ed Anderson wrote:

  Therefore, while  I don't have any data to support this, but I would be hesitant to  combine primary and secondary runners on the 13B NA for the reasons mentioned. 

Wow! 6 runners on the NA! Might make it easier to make the intake manifold. Variable length will be a challenge, though.

On the other hand the primary and secondary on the turbo (with the same timing)  would have air flow (as well as DIE pulses) all on the same timing and airflow cycle.  So I can't see why it wouldn't work to combine them. 

 

You may get some disturbance of the airflow, but the "Y" won't have much effect on the DIE pulse as it has no problem splitting and turning corners since the pulse is really not flowing air, but an pulse of energy translating across the distance by bumping one air molecule into the next.

Hm... I still don't see the difference from flowing water that mysteriously won't split evenly at the Y.

 

Also for my plans for a variable intake manifold, two tubes are much easier to deal with than four.  If I could have figured out a way to handle 4 tubes sliding I probably would have stayed with the four tubes.  However, for my turbo block, I decided the simplicity of using two tubes (combining primary and secondary) outweighed any disadvantage - I may prove myself wrong about that conclusion, but nothing ventured - nothing gained.

 

Ed Anderson