X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost05.isp.att.net ([207.115.11.55] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3882370 for flyrotary@lancaironline.net; Sun, 11 Oct 2009 12:28:48 -0400 Received-SPF: none receiver=logan.com; client-ip=207.115.11.55; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-157-211-223.mco.bellsouth.net[70.157.211.223]) by isp.att.net (frfwmhc05) with SMTP id <20091011162811H05005lbjue>; Sun, 11 Oct 2009 16:28:11 +0000 X-Originating-IP: [70.157.211.223] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: where's the missing power? Date: Sun, 11 Oct 2009 12:28:20 -0400 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01CA4A6E.51883760" X-Mailer: Microsoft Office Outlook 11 Thread-Index: AcpKjSVL7CKs4NJmTgG9I31ISjpXLgAAofgQ X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18005 This is a multi-part message in MIME format. ------=_NextPart_000_0006_01CA4A6E.51883760 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Yvon, I think your manifold pressure at full stop should read the same as your altimeter if it is set to the field elevation. Bill B _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Yvon Cournoyer Sent: Sunday, October 11, 2009 12:08 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: where's the missing power? 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 ------=_NextPart_000_0006_01CA4A6E.51883760 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Yvon,

I think your manifold pressure at full stop should read the same = as your altimeter if it is set to the field = elevation.

Bill B 

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Yvon Cournoyer
Sent: Sunday, October 11, = 2009 12:08 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = where's the missing power?

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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