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James, you seem to have summed it up very well. At the end of
the day it is what suits you and how much time you have to manufacture.
Starting from scratch and with the motor disassembled the P port is by far the
simplest and best but more costly to get the porting done say $800, but you then
save with time after that. As usual nothing is simple. Neil.
Sent: Friday, October 09, 2015 1:00 AM
Subject: [FlyRotary] Re: To P or not...
Back
to my question:
P-Port
pros: power, simple, reliable, NA
cons: tuning, long intakes, rebuild (assuming you have a side port built
already)
Turbo
pros: power, tuning less of a factor, short intakes, use side port short
block, altitude compensation
cons: more complicated, less reliable, more heat?
We haven’t really discussed different compression rotors. But the
Renesis has high compression rotors and is less suitable to turbo charging
without altering the rotors, right? If you already have a motor built with
side ports and low compression rotors (13B REW, 20B), it is ready for a turbo,
but P-Port would entail a significant rebuild, right?
Not the case for a turbo installation. Both the exhaust and intake of
turbo systems are just long enough to mount the turbo. Once you have the
intake charge well above ambient pressure, not much length tuning is
needed.
The ports and runner sizes in the turbo irons are enormous.
In the normally aspirated Pport both intake and exhaust lengths and
diameters make a big difference. Note the Mistral runner lengths. ( a side
port engine). Similar lengths would put best power in a Pport at a similar
RPM. The biggest effect will be muffler design. NA rotaries tune like dirt
bikes. Very sensitive to exhaust length, diameter and back pressure. The Le
mans engine had adjustable inlet lengths because it was an NA engine.
Lynn E. Hanover
Bill,
You couldn't be more incorrect. The P port is VERY
tuneable. Witness the LeMans 26B which had variable length intakes to
improve driveability across the rev range. You just need to alter your
thinking a bit. The rotor IS THE VALVE. When in the intake phase tuning
length is very effective. A turbo works similarly, but length isn't as
critical. Obstruction is more important in the turbo version. If the path is
clean and free of sharp corners the turbo doesn't work as hard and doesn't
heat the intake charge as much. Less need for an intercooler.
Bill Jepson
On Oct 7, 2015 4:35 PM, "Bill Bradburry" < flyrotary@lancaironline.net>
wrote:
If I understand
the situation, and believe me, I probably don’t….a tuned intake would give
a turbo more power at a given boost pressure than it would have untuned at
that same boost pressure. However, the benefit might not be worth
the effort due to the small incremental
difference.
On the other
hand, a P-port is never closed so there would be negligible reflected
waves to use for tuning. The rotor apex seal slides by the opening
of the port and slices off the fuel/air charge that is going to one rotor
face and it starts to be directed to the other face. Think of the
intake air column as a sausage that is being sliced off as the apex goes
by the open port. Very little reflectivity to use for
tuning.
Or more likely, I
could be wrong.
Bill
From:
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Wednesday, October 07, 2015
11:39 AM
To:
Rotary motors in aircraft
Subject: [FlyRotary] Re: To P or
not...
One more question to throw into the mix. A
friend is building a Cozy and has 13B short block, currently believed to
be fresh though compression and leak down tests remain to be done.
He is now thinking to go turbo instead of tearing it down to go
P-port. Is it true that there is no intake runner tuning for a turbo
setup? Yes it is more complicated to go turbo (than peripheral), but
there is also the advantages at altitude.
So the extra question is: P-port or
turbo?
Christian,
While you are
doing that, you could also include some info on your pporting of the
Renesis. How did you know where to bore the holes for proper
timing and how did you seal the water jacket? I assume that you
just plugged up the original ports with JB weld or
something?
Thanks,
One of the
other Bills
From:
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Wednesday, October 07, 2015
9:04 AM
To:
Rotary motors in aircraft
Subject: [FlyRotary] Re: To P or
not...
can you give details on
your custom built hotdog with inox?
baffling.
Sent:
Tuesday, October 06, 2015 11:08
PM
Subject:
[FlyRotary] Re: To P or
not...
I would agree, yes it
worked out to be allot more simpler running 2 x 2" runners than playing
with 4 in my opinion and easier to manufactur
etc
From modifying my engine
from a not so good 6 port intake to a simple 2 port intake I gained a
good 30-40 hp and 15 k top
end
The noise also isn't that
bad on my renises as I've attached a custom built hotdog underneath with
inox baffling which works
well
Trying to ensure I have
a complete knowledge before I make my
decision,
The P port as shown for
the website is exactly what we are looking for. Straight forward power
at high rpm. The noise is a factor of energy output which is the
same.
If I tune a 4 port
runner system and get x amount of air into the engine I give y amount
of fuel and I have z amount of power and engine exhaust/noise to
handle.
If I use a P port and
get x amount of air and give y amount of fuel it is the exact same z
output. It was just easier to get x amount of air into the
system.
Or am I completely off
base.
Bob,
One thing that
everyone should get clear is that for aircraft PPorts are almost
always superior. At higher RPMs. Also Pports will idle just fine.
Good balance and vibration control are the key to good idle. The
engine won't make a lot of power at low rpm but that isn't a problem
for an aircraft. The rotary makes a better aircraft engine than a
car engine!
Bill
Jepson
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