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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