Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2b2) with ESMTP id 3178809 for flyrotary@lancaironline.net; Mon, 19 Apr 2004 11:00:39 -0400 Received: from EDWARD (clt25-78-058.carolina.rr.com [24.25.78.58]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i3JF0aSn020593 for ; Mon, 19 Apr 2004 11:00:37 -0400 (EDT) Message-ID: <01ff01c4261e$ccf43f90$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: intake ideas? Date: Mon, 19 Apr 2004 10:58:39 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_01FC_01C425FD.45B09310" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_01FC_01C425FD.45B09310 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I agree with Al. My experience with larger diameter and shorter tubes = indicates they are not the best ticket for aircraft use where we = generally turn less than 7000 rpm. For the race car that turns 9000 and = above, short stacks clearly offer an advantage. However, air velocity = in the runners determines how well the combustion chamber is "stuffed". = Get the sizes too large and short and air velocity suffers at the lower = rpms we normally operate at. That does not mean you can't get into the air with the short stacks (I = did), but I found longer smaller diameter runners boosted my power = considerably at the rpms I operated at. However, at times, physical and = other constraints may dictate short stacks in which case, I wouldn't = hesitate to use shorter stacks - it will get you into the air and = flying. FWIW I don't sell manifolds, I just play with them {:>) Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Saturday, April 17, 2004 3:42 PM Subject: [FlyRotary] Re: intake ideas? Subject: [FlyRotary] Re: intake ideas? Russell, you will be on as solid ground as anyone else to simply use = the Atkins "short intake". I've visited with him extensively, visited his = shop and asked every question I could think of, and here's what Dave says = and I believe to be so on intake manifolds: We have 2 choices: 1) Long tuned manifolds that have more resistance = to mass flow of air, or 2) the short untuned manifold (used by Mazda = Racing??) which gives higher mass flow. - They both generate about same torque and HP but 2) has less = space problem. - Dave is a competive racer and is one of those guys with max experience with rotaries - and he is quite comfortable with the short manifold. I'm going to start off with the Atkins short manifold - or one similar = that fits the RX-8 Renesis engine. This topic has been hashed and re-hashed over the years, and it's a = little like the old 'blind man describing the elephant' story. When it = comes to hands-on experience and knowledge of the rotaries, Atkins is = probably 'da man'. When it comes to something departing from his = experience and into the realm of analysis or theory, Dave is definitely = 'anti'. And from a racing standpoint, where you may be running 7,000 - = 10,000 Rpm; short is good. On the other hand, both the analysis and dyno results make it = conclusive that there is performance benefit to tuned intake runners, = and it is especially applicable to aircraft application where we will = generally operate over a small rpm range, say 5000-5500 Rpm. This is a = different question than where you put the injectors, and there is some = reason to believe that having the primary close to the port, or in the = housing, is good. Having the secondary a bit further out may have an = advantage at higher air flow allowing more thorough vaporization and = mixing of the fuel. The question of tuned runners is 'how much is the benefit?', and 'what = do you want to give up for it'. Could maybe gain 4-7%. Compactness = inside the cowling can be an important factor. I went with short = manifold on my 20B based on wanting a compact configuration, and Atkins = convincing me that short was just as good. That was before I did much = analysis and studied dyno data. I'm happy with my installation, and the = dyno results show the performance is fine; but if I were starting over I = might look a bit longer at fitting in tuned runners.=20 My very flat torque curve is great for a car, but a bit more peaking = in the 5000-5500 to improve cruise economy in the plane would be nice. = What I have instead is the hp curve still going up in a nearly straight = line at 7000 rpm. The short manifold may be great for 2.85 : 1 redrive. = More pics and dyno results at http://members.cox.net/alg3/airplane.htm=20 FWIW, Al (obviously not at Fun-n-Sun) -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_01FC_01C425FD.45B09310 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I agree with Al.  My = experience with=20 larger diameter and shorter tubes indicates they are not the best ticket = for=20 aircraft use where we generally turn less than 7000 rpm.  For the = race car=20 that turns 9000 and above, short stacks clearly offer an = advantage. =20 However, air velocity in the runners determines how well the combustion = chamber=20 is "stuffed".  Get the sizes too large and short and air velocity = suffers=20 at the lower rpms we normally operate at.
 
That does not mean you can't get into = the air with=20 the short stacks (I did), but I found longer smaller diameter runners = boosted my=20 power considerably at the rpms I operated at.  However, at times, = physical=20 and other constraints may dictate short stacks in which case, I wouldn't = hesitate to use shorter stacks - it will get you into the air and=20 flying.
 
FWIW  I don't sell manifolds, I = just play with=20 them {:>)
 
Ed Anderson
RV-6A N494BW Rotary=20 Powered
Matthews, NC
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Saturday, April 17, 2004 = 3:42=20 PM
Subject: [FlyRotary] Re: intake = ideas?

 

Subject: [FlyRotary] Re: intake=20 ideas?

 

Russell, you will be on as solid ground as = anyone else=20 to simply use the

Atkins "short intake".  I've visited = with him=20 extensively, visited his shop

and asked every question I could think of, = and here's=20 what Dave says and I

believe to be so on intake=20 manifolds:

 

We have 2 choices:  1) Long tuned = manifolds that=20 have more resistance to

mass flow of air, or 2) the short untuned = manifold=20 (used by Mazda Racing??)

which gives higher mass = flow.

    -  They both = generate about=20 same torque and HP but 2) has less space

problem.

    -  Dave is a = competive racer=20 and is one of those guys with max

experience with rotaries - and he is quite = comfortable=20 with the short

manifold.

 

I'm going to start off with the Atkins short = manifold=20 - or one similar that

fits the RX-8 Renesis = engine.

 

This topic has been = hashed and=20 re-hashed over the years, and it=92s a little like the old =91blind = man describing=20 the elephant=92 story.  When it comes to hands-on experience and = knowledge=20 of the rotaries, Atkins is probably =91da man=92.  When it comes = to something=20 departing from his experience and into the realm of analysis or = theory, Dave=20 is definitely =91anti=92.  And from a racing standpoint, where = you may be=20 running 7,000 =96 10,000 Rpm; short is good.

 

On the = other hand,=20 both the analysis and dyno results make it conclusive that there is=20 performance benefit to tuned intake runners, and it is especially = applicable=20 to aircraft application where we will generally operate over a small = rpm=20 range, say 5000-5500 Rpm.  This is a different question than = where you=20 put the injectors, and there is some reason to believe that having the = primary=20 close to the port, or in the housing, is good.  Having the = secondary a=20 bit further out may have an advantage at higher air flow allowing more = thorough vaporization and mixing of the fuel.

 

The = question of=20 tuned runners is =91how much is the benefit?=92, and =91what do you = want to give up=20 for it=92.  Could maybe gain 4-7%.  Compactness inside the = cowling can=20 be an important factor.  I went with short manifold on my 20B = based on=20 wanting a compact configuration, and Atkins convincing me that short = was just=20 as good.  That was before I did much analysis and studied dyno = data.=20  I=92m happy with my installation, and the dyno results show the=20 performance is fine; but if I were starting over I might look a bit = longer at=20 fitting in tuned runners.

 

My very = flat=20 torque curve is great for a car, but a bit more peaking in the = 5000-5500 to=20 improve cruise economy in the plane would be nice.  What I have = instead=20 is the hp curve still going up in a nearly straight line at 7000 = rpm. =20 The short manifold may be great for 2.85 : 1 redrive.  More pics = and dyno=20 results at http://members.cox.net/= alg3/airplane.htm=20

 

FWIW,

Al = (obviously not=20 at Fun-n-Sun)

>>  Homepage: =20 http://www.flyrotary.com/
>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html
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