----- Original Message -----
Sent: Thursday, October 30, 2003 8:55
AM
Subject: [FlyRotary] Re: Intake
manifold
Ed, here's a highly theoretical question (as I have no plans to take
apart my engine again):
will street porting the 1986 NA narrow the intake
runner length curves on the graph?
On another note, I somehow have the
idea that it's a bad idea to combine the runners. For example Jim Mosur had
big problems splitting the water flow between his two radiators when he ran
them in parallel. Tracy has argued that it doesn't matter because on an intake
system you have a vacumn sucking in the air which would split it evenly.
However, not so with the DIE pulses. I could even imagine that the pulse,
preferring on path (one port) could even start to push out the air/fuel charge
out the other port.
Over to you...
Finn
First to answer you question. Ta = Ad/Ars. There
is a seperate Ta for each Ad (angular difference) between intake port opening
and other rotor's intake closing. So since porting would increases
Ad and therefore Ta for each port , what porting all three would do is simple
to increase the Ta for each port. This in effect is simply
changing one of the parmeters of the parametric equation L = 12*
Vp*(Ad-Pd)/Ars, Ad to be specific. Therefore, you will likely shift all
the curves higher. Depends on how much you port one vs the
other. The position of the curve would change but not the shape or slope
of the curve. Don't know if that answered your question or
not?
In many cases I think it is probably not a
good idea to combine runners. The NA 13B has basically 3 different port
timings (primary, secondary and aux). That means that air flow, pulses
what ever, would have to be different for all three or at least Primary and
the two others during engine operation. While perhaps not
impossible to get the primary and secondary of the 13B NA ported the
same, I seriously question whether that would be the best approach.
In fact, it might be better to have three different DIE points that the 13B NA
would appear to offer.
For instance, the secondary port could give you
DIE some place a bit above your static rpm to assist in take off, perhpas your
primary could give you a sweet spot at your climb rpm and perhaps the Aux port
could give you a sweet spot at high cruise rpm. There are lots of things
I/we still don't know about the DIE as implemented in the 13B. Remember
you get as many DIE sweet spots as you have different port timing. So
three for the 13B NA and actually perhaps as many as 6 spots for the
variable/switchable DIE system on the 1990 NA.
I think you have to decide where you would like a
bit more power. Me, if I had to pick one DIE rpm, I would want it
in the take off regime, I want to get off the ground and as high as possible
in as short amount of time as possible. Other folks, in carnard types,
might just want the DIE for cruise, etc.
Therefore, while I don't have any
data to support this, but I would be hesitant to combine primary and
secondary runners on the 13B NA for the reasons mentioned. On the other
hand the primary and secondary on the turbo (with the same timing) would
have air flow (as well as DIE pulses) all on the same timing and airflow
cycle. So I can't see why it wouldn't work to combine them.
You may get some disturbance of the airflow, but
the "Y" won't have much effect on the DIE pulse as it has no problem splitting
and turning corners since the pulse is really not flowing air, but an pulse of
energy translating across the distance by bumping one air molecule into the
next.
Also for my plans for a variable intake manifold,
two tubes are much easier to deal with than four. If I could have
figured out a way to handle 4 tubes sliding I probably would have stayed with
the four tubes. However, for my turbo block, I decided the simplicity of
using two tubes (combining primary and secondary) outweighed any disadvantage
- I may prove myself wrong about that conclusion, but nothing ventured -
nothing gained.
Ed Anderson