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In any case, the EDDIE = study=20 indicated that for my system that combining the primary and secondary = runners=20 after they exit the block not only would probably not hurt things, it = might=20 help. Well, it certainly simplified the tube alignment problem = and we=20 will see about its affect (if any) on = performance.

This puzzles me,=20 and maybe I missed some prior part of this discussion; but how do = avoid=20 getting a wave reflection; degradation or whatever at the junction of = two into=20 one?

Good = question.=20 Al.

=20 First, I am not an induction airflow expert. I have read a bit = about it=20 and you are correct, you can get harmful reflections at = intersections. =20 From what I understand (which may be incorrect), the amount of = reflected=20 energy you get depends on several things (can't remember them = all). One=20 of those factors is the type of convergence ("T" section or = "Y"=20 type for example), a second factor is the amount of change in = cross=20 section between the separate tubes and the single tube. Perhaps = how fast=20 they converge/diverge has an effect -but not certain about that=20 one. That's all I think I remember about intersections at the=20 moment.

The main = reason (as=20 far as I can see) for Mazda having a primary and secondary runner = system is=20 they have different timing for those ports. That would really = screw up=20 (in my opinion) the airflow if they had used just one = tube. Each=20 port with its different timing would be sending pulses through the = system and=20 sucking air out of sync and its doubtful (in my mind) that would = have=20 been beneficial.

It = also=20 permitted them to keep the airflow velocity high in the primary by = keeping the=20 runner and port size smaller promoting good chamber packing at lower=20 rpms. Then when they needed heavy breathing for the higher RPMS = they had=20 the secondary with its larger port and runners and different port=20 timing.

Now, for = those=20 reasons (and perhaps others), I can see why separating the runners for = automobile application had considerable merit. My statement was=20 to suggest that perhaps those factors are not as significant for = aircraft=20 application and therefore the simplicity of combining the runners = might have=20 benefit for the aircraft use that outweighed an adverse things as you=20 mentioned.

I could = be wrong of=20 course, and my next intake manifold (in progress as we chat) should = provide=20 some data on whether my combining intake runners helped or=20 hurt.

That's my = take on=20 it.