Dennis,
I'll try and
give you a more "detailed"
review of you analysis and approach in a short while (I have to dig up
a
drawing of the Renesis 4 port intake to look at). However, I seem to
recall that there is a valve in the air passages of the intake that
rotates
open or closed depending of some engine load variables. IF my memory
is
correct, this value in effect halves (or doubles depending on which
runner you
are using for reference) the distance the pulse has to travel from port
of one
rotor to port of the second rotor. At the right rpm range the value
closes forcing the pulse to travel the shorter distance (or else it
opens at
the lower RPM range to make the pulse travel a longer circuit – or vice
versa – I have to look and see if the Renesis even has such a valve –
the older N/A 13Bs did have the value in order to change the effective
length
of the intake runners.
I can not
tell from my hasty look at your
e mails whether you took that factor (the valve changing the effective
length
of the runner) into consideration or indeed, if the Renesis even has
one.
?
Will get
back to you shortly
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]
On
Behalf Of Dennis Haverlah
Sent: Thursday,
January 01, 2009
11:59 AM
To: Rotary motors in
aircraft
Subject: [FlyRotary]
Re:
Activity......
OK - I'll try to stirrup some reflective
comment on
the list.
I'm in the middle of trying to design a new intake for my RX-8 Renesis
powered
RV-7A
I've been reading the tuned intake discussion posts from 2004 and
2005.
FAW theory etc. I've tried
to apply the theories to the Mazda RX-8 4 port intake to see how it
works
and make sure it
agreed with the theories. No Luck!!?
My measurements of the cast aluminum intake show primary runners are
12.5 in.
long + 2.5 inch to the center of the chamber
where the intake runners from rotor 1 interact with rotor 2's intake
runners. Add 3 inches at the other end ( engine flange) for the
distance
from the
manifold flange to the center of the intake at the rotor face and the
total
intake is 18.0 inches. The secondaries are 1/2 inch longer at 18.5
inches.
It appears they are using the FAW wave created as Rotor #1 intake opens
to
travel through the intake tubes to Rotor #2. Total distance from
rotor
#1 to rotor #2 is 36 in. for primary runners and 37 in. for secondary
runners.
Ed's post of Aug. 26,04 indicated a "E" shaft rotation of 93 deg.
between Rotor #1 opening and Rotor #2 closing. I measured the angle on
an
old engine and agree.
The pulse from rotor #1 needs some opening to exit and at rotor #2 you
must
have some opening to enter the rotor. I'll guess this is a total of 10
deg. Hence we have about 83 deg of "E" shaft rotation
time for the pulse to travel from rotor #1 to rotor #2.
I want to design my intake for max. HP at 6750 rpm. 6750/60 = 112.5
rps;
1/112.5 = 0.008888rev/sec or for 360 deg rotation of the "E" shaft it
takes 8.888ms.
The time for 83 deg of "E" shaft rotation would be
8.888ms*83deg/360deg = 2.05ms. (the time available for the pulse to
travel from
rotor #1 to #2.)
speed of sound = 1100fps or 1.1f/ms*12 = 13.2 in/ms. So 13.2in/ms *
2.05 ms = 26.4 inch from rotor #1 to #2. My problem is this is already
5
in./ intake shorter than the RX-8 4 port intake. If I assume
their
intake is designed for 8500 rpm the calculation indicates a runner
length of 21.3
inches is needed between rotor
31 and #2. I measured the RX-8 cast al. intake to be 18 in * 2 =
36 in
.
To me it appears I do not understand how the RX-8 intake really
works!!
Anyone have any ideas or find an error with the logic?
Going FAW crazy!!
Dennis H.
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