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
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Copyright 1998-2003 All world wide rights reserved.
Paul Carey wrote:
Lyn and Paul
I will give you my experience with the Norton Rotary PPort.
I rode their bike and the engine seemed very smooth - remarkable. The long
intake runners had carbies at the end of them.
I purchased an engine, brought it back to Australia and fitted it to our
test truck with prop and accessories. The thing was a complete pig - bucking
and shaking the cabin and vibrating badly at idle and low revs. Norton did
not seem to have any answers, as they did not have the engine in an airframe
yet. I researched the work done with Powersport and their PP intake system,
and ended up just making new butterflies right at the housing - leaving the
long intake runners and carbies as they were (minus the butterflies).
Amazing difference - the engine purred with no vibration, accellerated easy,
and generally behaved itself very well. Unfortunately the aero company went
broke after that, so my testing came to a halt.
Just consider the 13B PP in a light airframe and the possible bad idle
characteristics.
PC
Paul Carey LAME, MC
Aero Management - aviation consultants.
www.aeromanagement.com.au
(08) 9371 5205 0418 959 892
The AirCraft Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/
Copyright 1998-2003 All world wide rights reserved.