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.
__________ Information from ESET
NOD32 Antivirus, version of virus signature database 3267 (20080714)
__________
The message was checked by ESET NOD32
Antivirus.
http://www.eset.com