X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from relais.videotron.ca ([24.201.245.36] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3882383 for flyrotary@lancaironline.net; Sun, 11 Oct 2009 12:08:53 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.201.245.36; envelope-from=geryvon@videotron.ca MIME-version: 1.0 Content-type: multipart/alternative; boundary="Boundary_(ID_5i+8QETU0IH5VE8lq/cbNg)" Received: from yvon ([66.130.84.106]) by VL-MO-MR004.ip.videotron.ca (Sun Java(tm) System Messaging Server 6.3-4.01 (built Aug 3 2007; 32bit)) with SMTP id <0KRC0010ZY5TYYA0@VL-MO-MR004.ip.videotron.ca> for flyrotary@lancaironline.net; Sun, 11 Oct 2009 12:08:17 -0400 (EDT) Message-id: <2AECF84D036F4A48B0D97A825AF5A2B0@yvon> From: Yvon Cournoyer To: Rotary motors in aircraft References: Subject: Re: [FlyRotary] where's the missing power? Date: Sun, 11 Oct 2009 12:08:03 -0400 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. --Boundary_(ID_5i+8QETU0IH5VE8lq/cbNg) Content-type: text/plain; charset=iso-8859-1 Content-transfer-encoding: 7BIT Mike, what is your vacuum reading at rest (full stop) ? To compare to my manifold pressure readings. Yvon ----- Original Message ----- From: Mike Wills To: Rotary motors in aircraft Sent: Saturday, October 10, 2009 11:27 PM Subject: [FlyRotary] where's the missing power? 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 --Boundary_(ID_5i+8QETU0IH5VE8lq/cbNg) Content-type: text/html; charset=iso-8859-1 Content-transfer-encoding: 7BIT
Mike, what is your vacuum reading at rest (full stop) ? To compare to my manifold pressure readings.
Yvon
----- Original Message -----
From: Mike Wills
Sent: Saturday, October 10, 2009 11:27 PM
Subject: [FlyRotary] where's the missing power?

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
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