Sent: Sunday, December 21, 2003 8:57
PM
Subject: [FlyRotary] Re: Dumb intake
question
What happens is when a Finite
Amplitude Wave (FAW) hits a change in cross-sectional area (like an opening
from your tube to the atmoshpere or a plenium - or a decrease to a closed
tube) energy is reflected back down the tube. The amount depends on the extent
of cross section change, but opening to the atmosphere reflects most of the
energy. If the cross sectional area it sees is Larger then a FAW wave
of the opposite type is reflected. If the cross sectional area is
smaller, a FAW wave of the same type is reflected.
Hi Ed,
Thanks for an explanation that was a clear as it
could possibly be. Now that you have confirmed that the change of cross
sectional area is what triggers the bounce, I can get back to a question that
I asked you a few months ago (Kelly just asked the same one).
Back when Eddie was first being discussed, I asked if
I could extend the runner ahead of the TB, and have it count as part of the
tuned assembly. At the time, you said no, that it had to be after
the TB. Is that your final answer :-)
If tuning is possible prior to the TB, then a short
manifold will work great, and offer easy tuning of the length.
Thanks,
Rusty (new cowl looks muuuuuch
better)
Well, can't
quite recall the details of that e mail-must be age{:>). If we were
talking EDDIE then I may have just misunderstood what your "ahead of the TB"
was actually referring to. But, in any case, if I stated that - then I
claim the right to change my mind {:>). You can tune to
benefical effect by paying attention to the length.
I had been focused on the port to
port (different rotors) in the EDDIE analysis and hadn't really tried the math
on the stand-alone-port. Also, I better understand how the pulse
returning to its orginating port would react
depending on whether the port is open or closed.
But, its fairly clear to me that the strength of the
effect is probably not the magnitude of the port to port EDDIE effect as some
energy is lost on each bounce. Also, the port event that you rely on
"the A" pulse rather than primarily the "B" pulse in the type of manifold you
are talking about also is somewhat weaker. But, its clearly
worthwhile.
I think I mentioned I found a 1970 Honda engineers
work that showed a boost in power based on "pulse" tuning AND his
work was for returning the pulse to the orginating port unlike the EDDIE
concept. But, try to keep the cross sectional area the same as much as
you can until your throttle body.
Ed Anderson