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From: "George Lendich" <lendich@optusnet.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2197170@logan.com>
Subject: Re: [FlyRotary] Re: carbs vs efi
Date: Wed, 25 Jul 2007 17:16:45 +1000
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Bill,
I bet your right, but the local engine builders tell me not as well as the 
Piston engines. They say it can't override restrictions to the extent a 
piston can, thus turning a restriction into velocity.
To be on the safe side, I take that into consideration when looking at port 
sizing, I discount any benefits of increased velocity.
George


> Hey George!
> The note is fine except for one thing. The rotary "sucks" or more to the 
> point vacuums just like a piston of similar size chambers. If it didn't it 
> would never start!
> Bill Jepson
>
>
> -----Original Message-----
> From: George Lendich <lendich@optusnet.com.au>
> To: Rotary motors in aircraft <flyrotary@lancaironline.net>
> Sent: Tue, 24 Jul 2007 3:10 pm
> Subject: [FlyRotary] Re: carbs vs efi
>
>
>
> Jerry,
>
> Sounds good!
>
> The Street port single will give about 116hp at 7,500, but you need 1.18 
> x2 sq" minimum ( 2.36 sq") = 44 Dia inlet.
>
>
>
> David McCandles has found some old info, which I will forward under 
> separate cover, which confirms these numbers although I haven't read it 
> through myself as yet.
>
>
>
> The RX8 uses smaller runners but more of them, the inlet area is massive 
> in total, the smaller runner maintains the velocity. However because the 
> Rotary doesn't suck like a piston engine ( sucking creates velocity) the 
> advantages of velocity over area needed, are limited.
>
>
>
> The 12A and 13B are the same size P-port 43mm, the timing/position are the 
> same.
>
> We have to start to accept that they know the advantages of sizing and 
> position.
>
> George
>
> George,? I just got back from Oshkosh which would have been a wasted trip 
> except that I got to fly a CH 701 amphib off the water.? This was a first 
> for ?yours truly. ? ?What a lot of fun.? The airplane handles perfectly 
> and is the right one for me. ? ?It is limited by the designer to 100 hp 
> and 200 lbs for the engine installation. So I am in the in enviable 
> situation of not wanting to get too much out of my p port. The plane was 
> powered by a 100 hp Rotax.? ?It did very well.? ?
>
>
>
> Re your analysis comparing side ports with p ports, I wonder if such an 
> analysis is even possible as they are quite different.? Anyway, I doubt 
> that a standard port can deliver 100 hp or a street port 130 hp. per 
> rotor, certainly not when limited to 7500 rpm.? Of course I am only 
> guessing.? No real knowledge or experience.??
>
>
>
>
> The only carb I saw at Oshkosh was the aero carb.? It is sized by HP and 
> they recommend the 38mm for? 125 to 160 hp.? This is too large for my 
> purposes.? I am considering going down to 35mm? (90 to 125 hp) ? ?The 
> problem is that I already have 38mm p ports.? Also, of interest is that 
> they do not recommend ram air. That simplifies the plumbing and the cowl. 
> ? ?The demo engine had rather long, small dia runners and an air filter 
> attached to the carb.? That is the "system." ((on an 80 hp v.w.))? ?If I 
> can get the drive figured out, ?I will build it with RB's aluminum side 
> plates and Atkins eccentric. ?BTW the 701 is a high wing. ?The system will 
> be strictly gravity. ? ?? ?Jerry
>
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>
> On Jul 21, 2007, at 10:14 PM, George Lendich wrote:
>
>
>
> 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 -----
>
>
> From: Jerry Hey
>
> To: Rotary motors in aircraft
>
> 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
>
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>
> Jerry
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> 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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