Return-Path: Received: from sccrmhc11.comcast.net ([204.127.202.55] verified) by logan.com (CommuniGate Pro SMTP 4.2b4) with ESMTP id 121344 for flyrotary@lancaironline.net; Wed, 02 Jun 2004 18:10:19 -0400 Received: from 204.127.205.149 ([204.127.205.149]) by comcast.net (sccrmhc11) with SMTP id <20040602220949011003fjd1e>; Wed, 2 Jun 2004 22:09:49 +0000 Received: from [68.51.44.162] by 204.127.205.149; Wed, 02 Jun 2004 22:09:49 +0000 From: kenpowell@comcast.net To: "Rotary motors in aircraft" Subject: intake dia. Date: Wed, 02 Jun 2004 22:09:49 +0000 Message-Id: <060220042209.10811.40BE502D0001904200002A3B220075894204040A99019F020A05@comcast.net> X-Mailer: AT&T Message Center Version 1 (May 18 2004) X-Authenticated-Sender: a2VucG93ZWxsQGNvbWNhc3QubmV0 MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="NextPart_Webmail_9m3u9jl4l_10811_1086214189_0" --NextPart_Webmail_9m3u9jl4l_10811_1086214189_0 Content-Type: text/plain Content-Transfer-Encoding: 8bit When Paul Yaw was on Paul L's list we had this same discussion but for a PP engine. He recommended starting with a 1.5" dia throttle body for each PP and stated that it should produce between 200 and 215 HP. He is obviously a proponent of high velocity in the intake tract. Ken Powell --NextPart_Webmail_9m3u9jl4l_10811_1086214189_0 Content-Type: message/rfc822 From: "Ed Anderson" To: "Rotary motors in aircraft" Subject: [FlyRotary] Re: Rev-2.1 part 2 Date: Wed, 2 Jun 2004 11:06:59 +0000 Content-Type: Multipart/alternative; boundary="NextPart_Webmail_9m3u9jl4l_10811_1086214189_1" --NextPart_Webmail_9m3u9jl4l_10811_1086214189_1 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageThe velocity aspect seems to carry a lot of weight in rotary = tuning. The reason I say that is my best power (thus far) has been with = the smallest diameter tubes. I have used TB with up to a 75MM opening = and have found them providing less desirable throttle response = characteristics. Not to say that large diameter tubes and throttle = bodies don't have their place. My personal opinion is that until you = are talking 9000+ rpm err on the side of smaller diameter tubes to keep = the velocity up. Tracy has hit 7200 rpm with his small tubes with his = 2.85, so I would think its a bit premature to worry about the 1.75" = being restrictive. Most credible studies/theories on intake tuning put a = lot of emphasis on intake runner velocity, in fact most quote a not to = exceed velocity of Mach 0.6!!! I believe that is the peak air velocity = of the surging intake charge while the average velocity is considerably = lower. =20 Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message -----=20 From: Russell Duffy=20 To: Rotary motors in aircraft=20 Sent: Tuesday, June 01, 2004 10:23 PM Subject: [FlyRotary] Re: Rev-2.1 part 2 Do you think 48-50mm's would boost power? Mo mix? The allout Racing = Beat wrap around intake uses 48MM Webers or Dellorto carbs. Dave Atkins = is really estute with that rig, so what does he say? TJ=20 One simple theory says that the largest throat possible will decrease = air flow resistance, and let the MAP get closer to the actual ambient = pressure. This ignores the more complicated theory that says that = higher velocity air through a smaller opening will help stuff more air = in the chamber. Everything is a compromise, so your best results will = be somewhere in between tiny, and huge. Ed will calculate this for you, = since he has no flying plane :-) Seriously, my 40 mm (which I didn't chose) has the same ID as the = 1.75" OD tubing that I used for runners. I doubt they're causing me any = problems now, but I do worry that it will be somewhat restrictive when I = get to the -C drive, and 7000+ rpm. If I end up matching Tracy's = static rpm with this setup, it will be interesting to see how I do with = the higher rpm configuration. =20 If you want to know what Dave has to say, give him a call. I've had = my last conversation with him. =20 Cheers, Rusty (low tolerance for BS) --NextPart_Webmail_9m3u9jl4l_10811_1086214189_1 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
The velocity aspect seems to carry a = lot of weight=20 in rotary tuning.  The reason I say that is my best power (thus = far) has=20 been with the smallest diameter tubes. I have used TB with up to a 75MM = opening=20 and have found them providing less desirable throttle response=20 characteristics.  Not to say that large diameter tubes and throttle = bodies=20 don't have their place.    My personal opinion is that = until you=20 are talking 9000+ rpm err on the side of smaller diameter tubes to keep = the=20 velocity up. Tracy has hit 7200 rpm with his small tubes with his = 2.85, so=20 I would think its a bit premature to worry about the 1.75" being = restrictive.=20 Most credible studies/theories on intake tuning put a lot of emphasis on = intake=20 runner velocity, in fact most quote a not to exceed velocity of Mach=20 0.6!!!  I believe that is the peak air velocity of the surging = intake=20 charge while the average velocity is considerably lower.  =
 
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From:=20 Russell=20 Duffy
Sent: Tuesday, June 01, 2004 = 10:23=20 PM
Subject: [FlyRotary] Re: = Rev-2.1 part=20 2

Do = you think=20 48-50mm's would boost power?  Mo mix?  The allout = Racing  Beat=20 wrap around intake uses 48MM Webers or Dellorto carbs.  Dave = Atkins=20 is really estute with that rig, so what does he = say?
TJ 
 
One = simple theory=20 says that the largest throat possible will decrease air = flow resistance, and let the MAP get closer to the actual ambient = pressure.  This ignores the more complicated theory that says = that higher=20 velocity air through a smaller opening will help stuff more air = in=20 the chamber.   Everything is a compromise, so your = best=20 results will be somewhere in between tiny, and huge.  Ed will = calculate=20 this for you, since he has no flying plane=20 :-)
 
Seriously, my 40 mm=20 (which I didn't chose) has the same ID as the 1.75" OD tubing = that I used=20 for runners.  I doubt they're causing me any problems now, but I = do worry=20 that it will be somewhat restrictive when I get to the -C drive, and = 7000+=20 rpm.   If I end up matching Tracy's static rpm with this=20 setup, it will be interesting to see how I do with the higher=20 = rpm configuration.  
 
If you want = to know what=20 Dave has to say, give him a call.  I've had my last = conversation=20 with him. 
 
Cheers,
Rusty (low = tolerance for=20 = BS)
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