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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