Paul
Thanks for the info. Something Fred said last year got me thinking
that if
the slide throttle hole in the throttle plate was designed correctly
(sort
of like a 'comma' mark on its side, only the top corner of the hole
could
be exposed during idle. This might possibly eliminate port overlap
during
low rpms.
Doug,
I doubt if it will eliminate overlap as this is the physical state in
regard
to the position of the ports.
What it may do is stage the inlet, something like the Mazda
carbies whereby the idle inlet (and manifold tube) is much smaller.
This may
increases inlet speed and improve idle, and throttle response at low
speeds,
but only if the manifold sized matched the inlet size.
A hard one to visualise!
George (down under)
George
Yes you are right. So much for late night ponderings. I just
realized that
the location of where the slide throttle opens first may not be so
relevant.
For example on the side or top. Air will still travel to the lower
part of
the intake p-port or said another way gases will seek the path of least
resistance.
Doug
Hi George/Doug;
One thing you might consider is a staged sideport/PPport
intake/throttle.
I've been meaning to get around to building one to test the idea but
haven't had the time.
The premise is to have a staged Pport slide throttle combination along
Paul's design for wide open throttle operation; and
a separate runner/butterfly for low speed/power operation using the
center iron side ports/injectors.
The plan was to have a single, small diameter (say 1") intake runner
supply air to the center iron intakes and fuel by the stock
center iron injectors. I can't remember the intake velocity
calculations but a smaller diameter could be tailored to provide
velocities for a stable idle and low power operation. Staging of the
PPort could take place around 3000rpm or so.
Why?
I believe Tracy Crook could run in this manner with his original carb
setup at reduced power.
The side port is supposed to be more efficient at lower power setting
according to Kenichi Yamamto's? book.
I am sure running on the center irons alone is not quite as good -
how much?
With a single runner, an idle air controller would also be an easy
addition.
Cheers
Cary
Cary
This has already been tried on an automobile using P-port and side ports.
on May 21st 2004 Tom Webber had the same inquiry. This is what Lynn, a
professional racer had to say about it.
Lynn, do you know of anyone using the side ports and P Ports for
and
intake configuration. I hear from different sources of poor idle
with P
Ports and that the power band is very narrow. I was thinking of
using
the side ports and have the P Ports open above 7000 RPM. Tom
Webber
The Pport idles quite a bit better than the bridge port. There is
much less
overlap on the Port. You can drive it around the paddock area as
though it were
a street car. It has very little power just off idle, but it is not
bucking
and back firing through the intake. The bridge ported engine is a
nasty mess to
drive just off idle. The idle is set at 2,000 RPM and attempts to
exceed that
with a load on it are met with a stalled engine or a bucking monster,
or
both. You have to slip the clutch quite a bit to get it going because
you need to
hold it at about 4,000 RPM. Once it is rolling fast enough,
everything is just
fine.
None of this applies to aircraft applications. The plate that carries
the
plastic damper units is more flywheel mass than we have and it is at
a larger
diameter, plus the flex plate mass is a help. So right there is a
big
improvement. Also the propeller system is a big flywheel that can
keep things going
smoothly.
On the Vintage rotaries web site there is a fellow who has both port
styles
in one engine and switches manifolds between the two with manifold
flange to
bloc off the unused ports. He claims that the open volume of the
unused ports is
not a problem.
He is driving this thing (an RX-3) on the street, so he has many
hours of
operation on both setups. He no doubt has a flywheel also, so he
would not see
the problems we have. Even with no rotating mass, the Pport idles
very smoothly.
It just doesn't like to go anywhere just off idle. A plane side port
would be
just the same as a street car and would be great for driving around
on the
ground.
If you build your own Pport, you could shorten the timing a bit and
move the
torque peak down the RPM band as much as possible. Higher runner
velocity and
more torque where you need it, around 6,000 RPM.
I think that both port styles at the same time would be a waste of
time.
Going from one to the other could be done. But it would be curing a
problem that I
have not seen. A fast idle to get warmed up and to the end of the
runway, and
then a gentle shove up to full throttle, then full rudder and a
little brake,
then shove the nose back down at 50 feet and wait for 100 knots and
a
vertical departure.
Lynn E. Hanover
Thanks Paul?
Don't remember seeing that message. Lots of Lynn's advice in my project
already...
Admittedly, the staged side/Pport makes more sense for a streetable car
than a plane.
One thing I should mention is I am also looking for good low power range
- a smooth
1500 rpm operation may be just fine.
Cheers
C
Are you building a sea plane? 1500 divided by 2.85 is 526 prop
RPM. Frankly you are not going to find it in a simple p-port.
It will idle at 1500 RPM but it is not what I would call
smooth compared to an RX8 side port engine with no overlap
at all. Even a third gen misses every now and then at 1500 RPM.
Paul Lamar ...No rotor no motor.
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