Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 811006 for flyrotary@lancaironline.net; Fri, 18 Mar 2005 21:27:15 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.rr.com [24.74.185.127]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j2J2QS0W025923 for ; Fri, 18 Mar 2005 21:26:29 -0500 (EST) Message-ID: <002f01c52c2b$1572fb40$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Intake Ideas.... Date: Fri, 18 Mar 2005 21:26:40 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002C_01C52C01.2C6604C0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_002C_01C52C01.2C6604C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable It all depends, Tom. I started out with short runners and a TWM twin = throat Webber with injectors (50mm each throat) as that was recommended = by the racing guys. Turns out (at least in my case) it was the wrong = combination for an aircraft engine turning in the 5000-6000 rpm range. = Changed to 21 inch runners (copied Tracy's Dynamic Manifold - with which = he won his first Sun & Fun 100 race). My static rpm increased from 5000 = to 5600 rpm, rate of climb increased 300 fpm and top speed increased = from 185 mph TAS to 194 MPH TAS. =20 The inertia of the air/fuel mixture is an important factor in stuffing = the combustion chamber. A inertia of a fast moving airstream will = continue to fill the chamber even after the rotor/piston starts to come = up from BDC. Smaller Dia and longer tubes generally favor the lower = RPM (5000-6000). Now if your engine is going to turn 7000+ rpm then I = would agree larger dia shorter tubes are called for. But with the = original 2.17 reduction drive 7000 rpm was a dream - now with the 2.85 = its within reach. I have hit 6800 rpm straight and level with the 21 = inch tubes. So I may revisit the first intake I took off and have = sitting on my bench. Even the Mazda LesMan race engine had approx = 12-17" of tube length (they had a variable length intake). Bill Eslick = tried very short runners (maybe even shorter than Atkins) and found = performance disappointing, he lengthened his intake runners and gained = considerably power. As with most things, a balancing of characteristics is called for. Too = small a dia tube and you are restricting flow - too large and you drop = airflow velocity. How important it is depends a great deal on what your = operating regime is. Big and short for high rpm, smaller and longer for = lower rpm. =20 One thing I have found is that it does not matter if you have an intake = capable of producing 250HP at 9000 rpm if your prop load keeps your = engine from getting above 6000 rpm, that intake not only does not do you = any good, but is probably hurting power production at your 6000 rpm = range. NOW if we had constant speed props it would be a bit different = story. You could hold the pitch fairly flat reducing prop load on the = engine and wind it up into the higher rpm ranges (producing increased = power) before loading the prop with more pitch. Or have a gear shifting = gear box {:>). Ed A ----- Original Message -----=20 From: Tom=20 To: Rotary motors in aircraft=20 Sent: Friday, March 18, 2005 8:27 PM Subject: [FlyRotary] Re: Intake Ideas.... Hi Dale,=20 20 inch runners are contrary to the experience of Tracy and Paul. = Both found that going from long to short runners made a noteworthy = improvement in performance. The pics I've seen of the Atkins intake, = like Paul's, has fairly short runners. I know sucking on short straws = is easier than sucking on long straws, sucking without a straw is even = easier. Other than allowing a single throttle-body to feed multiple = ports and being an approach to address possible airflow confusion, I'm = questioning the necessity of runners. I see I'm not the first to = raise the question and maybe the only one who doesn't know the answer. = I wanna know if its just a matter of unquestioned precedence but not = really necessary. It's something else I'd like to try. =20 Tom Dale Rogers wrote: Tom, It would _run_ ... but you would be giving away an=20 important benefit derived from having 20 or so inches=20 of individual runners: maximum fill of the combustion=20 chamber at 6000 RPM. I'm building an NA, so *I* can't afford to give that=20 away on my engine. Dale R. > ----- Original Message ----- From: Tom=20 >=20 >=20 > Imagine taking their plenum, cutting off the runners, and then = bolting this plenum onto the side of your motor over the intake ports = without using runners. Where the ported ends of the runners appear on = the inside of the plenum you have ported entries into your intake ports. = Oh, and then use an Ellison as a throttle-body. Is this wrong? >=20 >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html -------------------------------------------------------------------------= ----- Do you Yahoo!? Yahoo! Small Business - Try our new resources site! ------=_NextPart_000_002C_01C52C01.2C6604C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
It all depends, Tom.  I started = out with short=20 runners and a TWM twin throat Webber with injectors (50mm each throat) = as that=20 was recommended by the racing guys.  Turns out (at least in my = case) it was=20 the wrong combination for an aircraft engine turning in the 5000-6000 = rpm=20 range.  Changed to 21 inch runners (copied Tracy's Dynamic Manifold = - with=20 which he won his first Sun & Fun 100 race).  My static rpm = increased=20 from 5000 to 5600 rpm, rate of climb increased 300 fpm and top speed = increased=20 from 185 mph TAS to 194 MPH TAS. 
 
The inertia of the air/fuel mixture is = an important=20 factor in stuffing the combustion chamber. A inertia of a fast = moving=20 airstream will continue to fill the chamber even after the rotor/piston = starts=20 to come up from BDC.   Smaller Dia and longer tubes generally = favor=20 the lower RPM (5000-6000).  Now if your engine is going to turn = 7000+ rpm=20 then I would agree larger dia shorter tubes are called for.  But = with the=20 original 2.17 reduction drive 7000 rpm was a dream - now with the 2.85 = its=20 within reach.  I have hit 6800 rpm straight and level with the 21 = inch=20 tubes.  So I may revisit the first intake I took off and have = sitting on my=20 bench.  Even the Mazda LesMan race engine had approx 12-17" of tube = length=20 (they had a variable length intake).  Bill Eslick tried very short = runners=20 (maybe even shorter than Atkins) and found performance disappointing, he = lengthened his intake runners and gained considerably = power.
 
As with most things, a balancing of = characteristics=20 is called for.  Too small a dia tube and you are restricting flow - = too=20 large and you drop airflow velocity.  How important it is depends a = great=20 deal on what your operating regime is.  Big and short for high rpm, = smaller=20 and longer for lower rpm. 
 
One thing I have found is that it does = not matter=20 if you have an intake capable of producing 250HP at 9000 rpm if your = prop load=20 keeps your engine from getting above 6000 rpm, that intake not only does = not do=20 you any good, but is probably hurting power production at your 6000 rpm=20 range.  NOW if we had constant speed props it would be a bit = different=20 story.  You could hold the pitch fairly flat reducing prop load on = the=20 engine and wind it up into the higher rpm ranges (producing increased = power)=20 before loading the prop with more pitch.  Or have a gear shifting = gear box=20 {:>).
 
Ed A
 
 
 
 
 
----- Original Message -----
From:=20 Tom
Sent: Friday, March 18, 2005 = 8:27=20 PM
Subject: [FlyRotary] Re: Intake = Ideas....

Hi Dale,
20 inch runners are contrary to the experience of Tracy and=20 Paul.  Both found that going from long to short runners made a = noteworthy=20 improvement in performance.    The pics I've seen = of the=20 Atkins intake, like Paul's, has fairly short runners.   = I know=20 sucking on short straws is easier than sucking on long straws, sucking = without=20 a straw is even easier.     Other = than allowing a=20 single throttle-body to feed multiple ports and being an approach to = address=20 possible airflow confusion,  I'm questioning the necessity of=20 runners.    I see I'm not the first to raise the=20 question and maybe the only one who doesn't know the=20 answer.    I wanna know if its just a matter of = unquestioned=20 precedence but not really necessary.    It's = something=20 else I'd like to try.      
 
Tom


Dale Rogers <dale.r@cox.net> = wrote:
Tom,

It=20 would _run_ ... but you would be giving away an
important = benefit=20 derived from having 20 or so inches
of individual runners: = maximum fill=20 of the combustion
chamber at 6000 RPM.

I'm building an = NA, so *I*=20 can't afford to give that
away on my engine.

Dale=20 R.


> ----- Original Message ----- From: Tom
> =
>=20
> Imagine taking their plenum, cutting off the runners, and = then=20 bolting this plenum onto the side of your motor over the intake = ports=20 without using runners. Where the ported ends of the runners appear = on the=20 inside of the plenum you have ported entries into your intake ports. = Oh, and=20 then use an Ellison as a throttle-body. Is this wrong?
>=20


>> Homepage: http://www.flyrotary.com/
>> = Archive: = http://lancaironline.net/lists/flyrotary/List.html

Do you Yahoo!?
Yahoo! Small Business - Try=20 our new resources site! ------=_NextPart_000_002C_01C52C01.2C6604C0--