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Jerry,
I'm trying to compare the carb inlet area to port
or P-port areas.
Standard Port area 32 deg ATDC to 50 degree ABDC =
1.18 sq " each side (x2 = 2.36sq")- using the front and back housings
only.
A street port will be 1.5sq" x 2 =
3sq"
.
A 44mm P-port =
2.35sq"
A 42mm p-port = 2.14sq"
A 40mm P-port = 1.94sq"
A 38mm P-port = 1.75sq"
So you see a side port on a single has more port
area than a small P-port.
Perhaps the velocity will make up for less
area.
The street port is bigger again at 3 sq" - this
equates to 50mm port.
The standard port gives about 100 hp, the street
port about 130hp each rotor.
I wouldn't want to choke down the port areas with
too restrictive inlet carby area. I
can't see how a 38mm will cut the mustard when your own calculations suggest 1.6
P-port = 42mm sq".
In reality I'm only looking for 130HPat most, if I
can get that.
I can run a 41mm ID SS tube p-port with a 42mm
Carby ( and hope velocity makes up the difference) Or I can run with two 1.5
street ported side ports 3 sq" with two smaller carbs, perhaps
2x32mm.
BTW street ported 13B has been dynoed to 264hp
can't remember the RPM - it might have been higher than what we
run.
More confused than ever!
Does anyone know the IO/IC and size and HP of
the factory P-port.
Lynn, does the timing given, calculated by the
rotor uncovering and covering the port, or the side seal uncovering/covering the
port opening?
I was thinking the RX8 rotor will be slightly
different (bigger) with the harased edges.
George ( down under)
----- Original Message -----
Sent: Sunday, July 22, 2007 9:17 AM
Subject: [FlyRotary] Re: carbs vs
efi
George, maybe I have the wrong idea, but I don't
understand why you need such a large bore carb for the single rotor. No
way you are going to produce more than 150 hp. I think 38mm would be
enough. This is what Aero Carb recommends for the 0-320. Jerry
On Jul 21, 2007, at 5:56 PM, George Lendich wrote:
Jerry,
Looks like Pat was wrong about
Revmaster having a 44mm, the biggest they go to is 42mm ( at the present
time) and that costs $380. If I remember the 32mm costs
$320.
Jerry I would be interested in
feed back on what you thought about the Aero Carb, especially how it's
constructed - their all a little different.
I do like the Ellison but it's
too bloody expensive.
George ( down
under)
George,
the web site says $326.00. You might want to compare the aero carb
which is similar. http://www.aeroconversions.com
I will be looking at both at Oshkosh on Tuesday and Wednesday next
week. Jerry
On Jul 20, 2007, at 10:06 PM, George Lendich wrote:
I have been surprised at the recent
flurry of carb postings. I assumed that everyone was doing
EFI. having experienced total electrical failure in march on a
trip to the Bahamas I was thinking a lot about that Neanderthal carb
bolted under my O320 and the magnetos, all unaware of what was going
on in the radio, GPS, and nav lights
departments. the reality is that you don't want a
reserve battery to get you to the ground safely, you want to get to
the Bahamas and back and THEN look into what's
wrong.
my questions are "how much
power/performance is lost with a carb, and which carbs can do manual
mixture?". is it stupid to ask if the Lycoming carb could run a
13B? someone mentioned Harley carbs having a good
history of rough service. what about marvel/schebler? is
this question heresy? :-) isn't efi a bit of overkill for an
engine that basically runs at 100% power, 75% power and idle?
scanning thru the archives I see a lot of postings regarding mixture,
mapping, abrupt failures and such. does this complexity buy us
5%, 20%? the question of turbo-charging seems to beg
similar line of questioning.
kevin
Kevin,
It's probably my fault, with a
number of chaps helping me out with
information.
My Buddy Bill Jepson will tell you
nothing beats EFI and when it's running well, he's absolutely
right!
Not only that it is the best
for fuel efficiency, leaning reading fuel flow etc.
etc.
However I'm developing a single
rotor and looking at all sorts of issues including cost effectiveness
of less elaborate installations. I'm also not keen on high
pressure
fuel under the
cowl.
Most importantly I'm not an
electronics person and seeing the problems experienced by others has
me more than a little nervous, in regard to
EFI.
Of course I know very little about
carbies, so their helping me with this as
well.
The Revmaster might be the choice
for me, but I'm awaiting the sticker shock!
George ( down
under)
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