I expected t= his drop.  For reasons of not wanting to enter a prolonged and = fruitless discussion on rotary engine manifold design, I will not explain= why this drop is desirable : )

Oh; come on =E2=80=93 gives us the 25 = words or less version =E2=80=93 well; maybe 50 words. We promise no prolo= nged and fruitless discussion.

Al

Damn, I'm such a sucker for that line.

Most gear head= s already understand that successful= intake tuning is the art and science of maximizing and managing the ener= gy represented by the moving mass of air in the manifold as it accelerate= s and decelerates. But, there are some less obvious subtleties= at work in the Mazda rotary manifold.
I believe Mazda's inten= t on the 2nd gen NA rotary was to intentionally restrict the flow on= the primary ports so as to increase the velocity in the larger secondari= es. This goal is also aided by opening the secondaries a bit sooner= than the primaries (gets the train moving early). Note that portin= g (enlarging) the primaries or making the primary runners larger may= be counterproductive here so the time honored tradition of "bigger = is better" will lead you the wrong way. The resultant higher veloci= ty in the secondary runners is then used to increase VE wi= th the later closing secondary port. So why not close up the primar= ies completely and get even higher velocity in the secondary?  = It's all about finding the point of diminishing returns.
Tracy (way past 5= 0 word limit)

Tracy's analysis so= unds reasonable to me. Its clear that Mazda expected some benefit i= n going to the trouble and expense of keeping the primary and secondary r= unners and port timing different. I had wondered why they would hav= e the secondary port open before the primary port (6 port engine) and I t= hink Tracy's hypothesis is probably correct - at least it makes sense.&nb= sp;

I ported both my primary and secondary to the same port timi= ng and concluded that since the ports now had the same timing that I coul= d merge the secondary and primary ports with minimum adverse effect. = ; My testing will hopefully show that to be correct.

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC

= There is a good chance your approach will work fine. Mazda's attemp= t at this juggling act was flawed due to the horribly dirty path in the s= econdary aux ports on the NA manifold & block.   I think th= at is why my turbo block (much cleaner ports) worked about as well as&nbs= p;my earlier 6 port block, even though the later port timing on the = 6 port is theoretically better.

Tracy