In any case, the EDDIE study
indicated that for my system that combining the primary and secondary runners
after they exit the block not only would probably not hurt things, it might
help. Well, it certainly simplified the tube alignment problem and we
will see about its affect (if any) on performance.
This puzzles me,
and maybe I missed some prior part of this discussion; but how do avoid
getting a wave reflection; degradation or whatever at the junction of two into
one?
Al
Good question.
Al.
First, I am not an induction airflow expert. I have read a bit about it
and you are correct, you can get harmful reflections at intersections.
From what I understand (which may be incorrect), the amount of reflected
energy you get depends on several things (can't remember them all). One
of those factors is the type of convergence ("T" section or "Y"
type for example), a second factor is the amount of change in cross
section between the separate tubes and the single tube. Perhaps how fast
they converge/diverge has an effect -but not certain about that
one. That's all I think I remember about intersections at the
moment.
The main reason (as
far as I can see) for Mazda having a primary and secondary runner system is
they have different timing for those ports. That would really screw up
(in my opinion) the airflow if they had used just one tube. Each
port with its different timing would be sending pulses through the system and
sucking air out of sync and its doubtful (in my mind) that would have
been beneficial.
It also
permitted them to keep the airflow velocity high in the primary by keeping the
runner and port size smaller promoting good chamber packing at lower
rpms. Then when they needed heavy breathing for the higher RPMS they had
the secondary with its larger port and runners and different port
timing.
Now, for those
reasons (and perhaps others), I can see why separating the runners for
automobile application had considerable merit. My statement was
to suggest that perhaps those factors are not as significant for aircraft
application and therefore the simplicity of combining the runners might have
benefit for the aircraft use that outweighed an adverse things as you
mentioned.
I could be wrong of
course, and my next intake manifold (in progress as we chat) should provide
some data on whether my combining intake runners helped or
hurt.
That's my take on
it.
Ed