X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3882582 for flyrotary@lancaironline.net; Sun, 11 Oct 2009 17:12:31 -0400 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (sv1-1.per.aanet.com.au [203.24.100.68]) by poplet2.per.eftel.com (Postfix) with ESMTP id 865D81738FD for ; Mon, 12 Oct 2009 05:11:56 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id A9286BEC011 for ; Mon, 12 Oct 2009 05:11:55 +0800 (WST) Message-ID: From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: where's the missing power? Date: Mon, 12 Oct 2009 07:11:59 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0011_01CA4B0B.4A477180" 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 X-Antivirus: avast! (VPS 091011-0, 10/11/2009), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0011_01CA4B0B.4A477180 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Bill, I checked your numbers and found them correct, However the 3" (76mm) = butterfly is there to make sure that there is sufficient air in the = plenum for each inlet tube to draw upon and doesn't necessarily equate = to what the engine needs at any particular time other than more than = adequate at full power. Considering there is a restriction in front of = this butterfly (an air filter), I would bet it's sized correctly at 7 = cu".=20 The same applies to the exhaust any restriction will build back = pressure, as Lynn stated. If you looked into the maths of expanded gases = volume which was measured at 7.8 bar absolute at 6,000RPM or 100 PSI = (or 6.8 times 40 cu") and speed of exhaust of 714 ft sec ( at 6,000 rpm) = and supersonic at initial openings - the 4" at Lynn's RPM don't seem = unreasonable at higher RPM. =20 Just some useless data for those interested. George ( down under) 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. =20 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.=20 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)=20 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! =20 Bill B =20 -------------------------------------------------------------------------= ----- 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. =20 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. =20 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. =20 Any comments on this or ways to test it are welcome. =20 Mike Wills RV-4 N144MW ------=_NextPart_000_0011_01CA4B0B.4A477180 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Bill,
I checked=20 your numbers and found them correct, However the 3" (76mm) butterfly is = there to=20 make sure that there is sufficient air in the plenum for each inlet = tube to=20 draw upon and doesn't necessarily equate to what the engine needs at any = particular time other than more than adequate at full power. Considering = there=20 is a restriction in front of this butterfly (an air filter), I would bet = it's=20 sized correctly at 7 cu". 
The same=20 applies to the exhaust any restriction will build back pressure, as Lynn = stated.=20 If you looked into the maths of expanded gases volume which was measured = at=20  7.8 bar absolute at 6,000RPM or 100 PSI (or 6.8 times 40 cu") and = speed of=20 exhaust of 714 ft sec ( at 6,000 rpm)  and supersonic at = initial=20 openings - the 4" at Lynn's RPM don't seem unreasonable at higher=20 RPM.
 
Just some=20 useless data for those interested.
George (=20 down under)

This phenomenon  has been bothering me = for quite=20 some time.  I doubt anyone has noticed this in a car and I have = not=20 convinced myself that it should be happening in our = installations. =20

Tracy = once=20 remarked that the throttle body might not be the most restrictive = point in the=20 intake.  I have the Renesis.  The stock intake tubes are = about 1.125=20 in diameter where they are cut in my installation.  The stock = throttle=20 body in the Renesis is 75MM and is electrically controlled.  When = Tracy got=20 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=20 the throttle body somewhere around 7 depending on what is lost by the = presence=20 of the butterfly.  Tracy was correct! (big surprise=20 :>))

I know of one bypass of the throttle body in = the stock=20 intake and there may be others that I don=92t know about.  The = one is=20 filtered air just prior to the throttle body that goes to a 5/16 tube = at the=20 bottom center of the intake.  It feeds two small tubes that are = inserted=20 into the primary ports.  The purpose is to give a blast to the = fuel=20 during idle to help break up fuel droplets.  I asked Tracy what = to do about=20 this opening and he said I could use it or block it didn=92t = matter.  I am=20 using it as a vacuum port for my fuel pressure regulator.  (but = planning=20 to change that to its original use)

This port will move lots of air at idle and = very=20 little at WOT. (depending on the intake restriction)  it would = improve=20 the top end, but probably very little.

This port could be used to find your total = intake=20 system restriction.  If you connect a manometer or magnehelic = guage to=20 this port and run the engine at full throttle,  the inches of = water will=20 equal the total restriction. (if you use a manometer, all the water = will be=20 sucked out anywhere close to idle.  You will need a valve to = protect it)=20

Maybe in the car the restriction prior to = the throttle=20 body takes care of the difference in sizes of the = tubes/throttle.  Maybe=20 there are other bypasses that I don=92t know=20 about???

This is an area of a lot of learning = opportunity for=20 those of you who have a running engine (I don=92t right now = [:>( =20 )

My manifold pressure guage correlated well = with my=20 several altimeters with the engine off.   When my engine was = running, prop blast would give me about 30.5 inches of manifold = pressure at=20 WOT measured after the throttle body and prior to the 4 = primary/secondary=20 tubes.  I never measured the pressure at the primary intake=20 ports.

I think a lot could be learned by measuring = the intake=20 port pressures at different throttle = settings.

Publish anything you=20 find!

 

Bill B

 

From: Rotary=20 motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike = Wills
Sent: Saturday, October 10, = 2009 11:28=20 PM
To: Rotary = motors in=20 aircraft
Subject: = [FlyRotary]=20 where's the missing power?

I noticed quite a while = ago and=20 have mentioned several times here that my engine does not have a = linear=20 response to throttle. It reaches its max power before it reaches fully = open=20 throttle. I havent worried too much about this up until now because = the=20 airplane has sufficient power as is, has slightly better performance = than my=20 previous 160HP Lyc powered -6A, and my wood prop is actually a pretty = good=20 match for the current power level.

 

But I would like to = understand=20 what's going on here and eventually address it. I was flying = yesterday, my=20 usual boring holes in the sky directly over the airport. Decided to=20 investigate just a little so leveled at 5,000 feet at full throttle. = Started=20 reducing throttle until I noticed a slight reduction in RPM and fuel = flow.=20 Then looked down at where the throttle was actually set and was = shocked to see=20 it slightly below half open. I dont have a regular manifold pressure = gauge,=20 just an industrial type vacuum gauge ( I really gotta get an MP = gauge).=20 Anyway, the vacuum gauge was indicating 4" of=20 vacuum.

 

So I suspect I am giving = up a=20 substantial amount of HP. I think the most likely suspect is my = throttle body.=20 For a throttle body I copied Tracy's original design. Started = with a stock=20 late 80s Mazda TB and hacked off the third port and all of the extra = stuff.=20 The cowl in this area is very tight and I am unable to install any = sort of air=20 filter or any sort of bell mouth on the TB. And I'm sure the cowl's = close=20 proximity to the TB influences airflow into it as=20 well.

 

Any comments on this or = ways to=20 test it are welcome.

 

Mike=20 Wills

RV-4=20 = N144MW

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