X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao107.cox.net ([68.230.241.39] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3882147 for flyrotary@lancaironline.net; Sat, 10 Oct 2009 23:28:14 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.39; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo02.cox.net ([70.169.32.72]) by fed1rmmtao107.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20091011032737.VZIF21470.fed1rmmtao107.cox.net@fed1rmimpo02.cox.net> for ; Sat, 10 Oct 2009 23:27:37 -0400 Received: from wills ([68.105.87.66]) by fed1rmimpo02.cox.net with bizsmtp id rFTd1c0021RstZw04FTeXa; Sat, 10 Oct 2009 23:27:39 -0400 X-VR-Score: 0.00 X-Authority-Analysis: v=1.0 c=1 a=5MdhjMwTZjk68CaDIuAA:9 a=QhQSANPlgFxU_LCt_PIA:7 a=2YnrZCr706epGfPrZwWq_PU43JgA:4 a=CkMHG4f3T0tW0E1OL94A:9 a=xIm82SAA9uAkMkhZ7MkA:7 a=QCsDD9YGyid3L_xR2yPt37ddJe0A:4 X-CM-Score: 0.00 Message-ID: <410955991DB04457B545D1A3C7891404@wills> From: "Mike Wills" To: "Rotary motors in aircraft" Subject: where's the missing power? Date: Sat, 10 Oct 2009 20:27:38 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001F_01CA49E8.1C199780" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_001F_01CA49E8.1C199780 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I noticed quite a while ago and have mentioned several times here that = my engine does not have a linear response to throttle. It reaches its = max power before it reaches fully open throttle. I havent worried too = much about this up until now because the airplane has sufficient power = as is, has slightly better performance than my previous 160HP Lyc = powered -6A, and my wood prop is actually a pretty good match for the = current power level. But I would like to understand what's going on here and eventually = address it. I was flying yesterday, my usual boring holes in the sky = directly over the airport. Decided to investigate just a little so = leveled at 5,000 feet at full throttle. Started reducing throttle until = I noticed a slight reduction in RPM and fuel flow. Then looked down at = where the throttle was actually set and was shocked to see it slightly = below half open. I dont have a regular manifold pressure gauge, just an = industrial type vacuum gauge ( I really gotta get an MP gauge). Anyway, = the vacuum gauge was indicating 4" of vacuum. So I suspect I am giving up a substantial amount of HP. I think the most = likely suspect is my throttle body. For a throttle body I copied Tracy's = original design. Started with a stock late 80s Mazda TB and hacked off = the third port and all of the extra stuff. The cowl in this area is very = tight and I am unable to install any sort of air filter or any sort of = bell mouth on the TB. And I'm sure the cowl's close proximity to the TB = influences airflow into it as well. Any comments on this or ways to test it are welcome. Mike Wills RV-4 N144MW ------=_NextPart_000_001F_01CA49E8.1C199780 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I noticed quite a while ago and have = mentioned=20 several times here that my engine does not have a linear response to = throttle.=20 It reaches its max power before it reaches fully open throttle. I havent = worried=20 too much about this up until now because the airplane has sufficient = power as=20 is, has slightly better performance than my previous 160HP Lyc powered = -6A, and=20 my wood prop is actually a pretty good match for the current power=20 level.
 
But I would like to understand what's = going on here=20 and eventually address it. I was flying yesterday, my usual boring holes = in the=20 sky directly over the airport. Decided to investigate just a little so = leveled=20 at 5,000 feet at full throttle. Started reducing throttle until I = noticed a=20 slight reduction in RPM and fuel flow. Then looked down at where the = throttle=20 was actually set and was shocked to see it slightly below half open. I = dont have=20 a regular manifold pressure gauge, just an industrial type vacuum gauge = ( I=20 really gotta get an MP gauge). Anyway, the vacuum gauge was indicating = 4" of=20 vacuum.
 
So I suspect I am giving up a = substantial amount of=20 HP. I think the most likely suspect is my throttle body. For a throttle=20 body I copied Tracy's original design. Started with a stock late = 80s Mazda=20 TB and hacked off the third port and all of the extra stuff. The cowl in = this=20 area is very tight and I am unable to install any sort of air filter or = any sort=20 of bell mouth on the TB. And I'm sure the cowl's close proximity to the = TB=20 influences airflow into it as well.
 
Any comments on this or ways to test it = are=20 welcome.
 
Mike Wills
RV-4 N144MW
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