X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost01.isp.att.net ([204.127.217.101] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3882359 for flyrotary@lancaironline.net; Sun, 11 Oct 2009 11:11:08 -0400 Received-SPF: none receiver=logan.com; client-ip=204.127.217.101; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-157-211-223.mco.bellsouth.net[70.157.211.223]) by isp.att.net (frfwmhc01) with SMTP id <20091011151030H0100jho94e>; Sun, 11 Oct 2009 15:10:30 +0000 X-Originating-IP: [70.157.211.223] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] where's the missing power? Date: Sun, 11 Oct 2009 11:10:38 -0400 Message-ID: <00134CE352E94563BA5C6540F2C90136@Desktop> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001E_01CA4A63.7725E3B0" X-Mailer: Microsoft Office Outlook 11 Thread-Index: AcpKIt/xBY1hls/eTUKrWxplX6a6XQAV/oVg X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18005 This is a multi-part message in MIME format. ------=_NextPart_000_001E_01CA4A63.7725E3B0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Mike, This phenomenon has been bothering me for quite some time. I doubt anyone has noticed this in a car and I have not convinced myself that it should be happening in our installations. Tracy once remarked that the throttle body might not be the most restrictive point in the intake. I have the Renesis. The stock intake tubes are about 1.125 in diameter where they are cut in my installation. The stock throttle body in the Renesis is 75MM and is electrically controlled. When Tracy got delayed in developing his throttle control, I purchased an aftermarket throttle body that is, I think, 76 MM. So, the tubes have about 4 square inches of area, and the throttle body somewhere around 7 depending on what is lost by the presence of the butterfly. Tracy was correct! (big surprise :>)) I know of one bypass of the throttle body in the stock intake and there may be others that I don't know about. The one is filtered air just prior to the throttle body that goes to a 5/16 tube at the bottom center of the intake. It feeds two small tubes that are inserted into the primary ports. The purpose is to give a blast to the fuel during idle to help break up fuel droplets. I asked Tracy what to do about this opening and he said I could use it or block it didn't matter. I am using it as a vacuum port for my fuel pressure regulator. (but planning to change that to its original use) This port will move lots of air at idle and very little at WOT. (depending on the intake restriction) it would improve the top end, but probably very little. This port could be used to find your total intake system restriction. If you connect a manometer or magnehelic guage to this port and run the engine at full throttle, the inches of water will equal the total restriction. (if you use a manometer, all the water will be sucked out anywhere close to idle. You will need a valve to protect it) Maybe in the car the restriction prior to the throttle body takes care of the difference in sizes of the tubes/throttle. Maybe there are other bypasses that I don't know about??? This is an area of a lot of learning opportunity for those of you who have a running engine (I don't right now [:>( ) My manifold pressure guage correlated well with my several altimeters with the engine off. When my engine was running, prop blast would give me about 30.5 inches of manifold pressure at WOT measured after the throttle body and prior to the 4 primary/secondary tubes. I never measured the pressure at the primary intake ports. I think a lot could be learned by measuring the intake port pressures at different throttle settings. Publish anything you find! Bill B _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills Sent: Saturday, October 10, 2009 11:28 PM To: Rotary motors in aircraft 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_001E_01CA4A63.7725E3B0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Mike,

This phenomenon  has been bothering me for quite some = time.  I doubt anyone has noticed this in a car and I have not convinced myself = that it should be happening in our installations.  =

Tracy once remarked that the throttle body might not be the most restrictive = point in the intake.  I have the Renesis.  The stock intake tubes are = about 1.125 in diameter where they are cut in my installation.  The stock throttle body in the Renesis is 75MM and is electrically = controlled.  When Tracy got delayed in developing his throttle control, I purchased an aftermarket = throttle body that is, I think, 76 MM.

So, the tubes have about 4 square inches of area, and the = throttle body somewhere around 7 depending on what is lost by the presence of the butterfly.  Tracy was correct! (big surprise :>))

I know of one bypass of the throttle body in the stock intake = and there may be others that I don’t know about.  The one is filtered = air just prior to the throttle body that goes to a 5/16 tube at the bottom center = of the intake.  It feeds two small tubes that are inserted into the = primary ports.  The purpose is to give a blast to the fuel during idle to = help break up fuel droplets.  I asked Tracy what to do about this opening and he said I could use it or block it = didn’t matter.  I am using it as a vacuum port for my fuel pressure = regulator.  (but planning to change that to its original = use)

This port will move lots of air at idle and very little at WOT. (depending on the intake restriction)  it would improve the top = end, but probably very little.

This port could be used to find your total intake system = restriction.  If you connect a manometer or magnehelic guage to this port and run the = engine at full throttle,  the inches of water will equal the total = restriction. (if you use a manometer, all the water will be sucked out anywhere close = to idle.  You will need a valve to protect it) =

Maybe in the car the restriction prior to the throttle body = takes care of the difference in sizes of the tubes/throttle.  Maybe there are = other bypasses that I don’t know about???

This is an area of a lot of learning opportunity for those of = you who have a running engine (I don’t right now [:>(  = )

My manifold pressure guage correlated well with my several = altimeters with the engine off.   When my engine was running, prop blast = would give me about 30.5 inches of manifold pressure at WOT measured after the throttle body and prior to the 4 primary/secondary tubes.  I never measured the pressure at the primary intake = ports.

I think a lot could be learned by measuring the intake port = pressures at different throttle settings.

Publish anything you find!

 

Bill B

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Saturday, October = 10, 2009 11:28 PM
To: Rotary motors in = aircraft
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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