X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao103.cox.net ([68.230.241.43] verified) by logan.com (CommuniGate Pro SMTP 5.2.0) with ESMTP id 2713997 for flyrotary@lancaironline.net; Mon, 04 Feb 2008 01:01:34 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.43; envelope-from=alventures@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao103.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20080204060055.BPMX14980.fed1rmmtao103.cox.net@fed1rmimpo01.cox.net> for ; Mon, 4 Feb 2008 01:00:55 -0500 Received: from BigAl ([72.192.137.74]) by fed1rmimpo01.cox.net with bizsmtp id lJ0p1Y00T1cVYgg0000000; Mon, 04 Feb 2008 01:00:49 -0500 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Low compression rotors Date: Sun, 3 Feb 2008 22:01:50 -0800 Message-ID: <000001c866f3$6edf6780$6401a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C866B0.60BC2780" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C866B0.60BC2780 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable =20 I have a 20B that I have taken the turbos off and will be using it in an aircraft, a RV-10. A friend of mine said that I should use the 9.7 compression rotors instead of the turbo rotors. What say you all? =20 =20 I was very disappointed when I learned that Atkins did not switch out = the 9.0 rotors for the 9.7 for my NA 20B. My research turned up a plot of = BMEP (same as power other things being equal) vs rpm for different = compression ratios done by Mazda. The effect depends on RPM - basically above about 6000 replacing the 9.0 with the 9.7 will have little effect, and the expected effect is about 4% around 5200 rpm. =20 If you are planning a 2.17 : 1 redrive; then I'd suggest making the = change because the 5000 - 5500 rpm is important operating range. If you go for = the 2.85 ratio then it is probably not worth it. =20 Al ------=_NextPart_000_0001_01C866B0.60BC2780 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I have a 20B that I have taken the turbos off and will be using it in = an

aircraft, a RV-10. A friend of mine said that I should use the = 9.7

compression rotors instead of the turbo rotors. What say you all? =

<= /font>

I was very = disappointed when I learned that Atkins did not switch out the 9.0 rotors for the 9.7 = for my NA 20B. My research turned up a plot of BMEP (same as power other things being equal) vs rpm for different compression ratios done = by Mazda. The effect depends on RPM – basically above about 6000 = replacing the 9.0 with the 9.7 will have little effect, and the expected effect is = about 4% around 5200 rpm.

If you are = planning a 2.17 : 1 redrive; then I’d suggest making the change because the 5000 = – 5500 rpm is important operating range. If you go for the 2.85 = ratio then it is probably not worth it.

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