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 3885962 for flyrotary@lancaironline.net; Wed, 14 Oct 2009 16:51:00 -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 F005F1739EC for ; Thu, 15 Oct 2009 04:50:21 +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 3690BBEC00D for ; Thu, 15 Oct 2009 04:50:20 +0800 (WST) Message-ID: From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: intake manifold 13b 86 Date: Thu, 15 Oct 2009 06:50:21 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01CA4D63.C3A79000" 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 091014-0, 10/14/2009), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0009_01CA4D63.C3A79000 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Chris,=20 I'm sure your right, just looking for a general indication of the = secondaries coming in to play. My reason is that I was looking at a CAD drawing I did of the engine = and noticed that the primaries are placed lower than the secondaries and = thought they may have come in earlier. However they come in a few degree = after the secondaries and close a few degrees before the secondaries. My thinking is, a later opening coupled with higher velocity counters = the ( any ) back 'exhaust' pressure and minimizes any contamination of = the incoming charge, maximizing VE at low RPM/ Idle.=20 A later closing counter any possible back 'compression' pressure. All things being equal, the higher RPM minimizes both these = situations. At higher RPM the exhaust velocity is higher and tends to be = self evacuating, reducing any exhaust back pressure and might even = create some vacuum, sucking some incoming charge into the exhaust. The = larger secondary inlet and will have a higher velocity (now) helping = overcome and compression back pressure. I just feel ( for my own benefit) it's interesting to know when all = this is going on - at approximately what RPM.=20 I believe Tracy holds back the inlet charge timing to accommodate = these changes and has the fuel injection at the optimum time - even at = higher RPM I don't think he injects until the exhaust is closed. This is = ideal for the larger lower velocity PP but I don't think it can be done = with a carbie. I mention these things for the chap wondering about the primary inlet = ports. =20 George ( down under) George, I do not believe stagging is based on RPM but instead Manifold = Pressure (MP). By default, IIRC, Tracy has it at 15.5. Should that = conflict to a cruise or often used setting, such as on final, it is = pretty easily changed by selecting....I think, Mode 7, increasing the = throttle to the desired MP and then pressing the Program button when at = the desired MP/RPM. That will set it to that chosen MP/RPM. FWIW. All the best, Chris Barber Houston Cpl Christopher Barber, JD. Badge 330 Bellaire Police Department 5100 Jessamine Bellaire, Texas 77401 713-668-0487 CBarber@BellariePolice.com -------------------------------------------------------------------------= ----- From: Rotary motors in aircraft [flyrotary@lancaironline.net] On = Behalf Of George Lendich [lendich@aanet.com.au] Sent: Tuesday, October 13, 2009 3:48 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: intake manifold 13b 86 Lynn,=20 About what RPM does the secondaries come in, if I go by memory, which = isn't always the best thing for mew to do, It's about 3500 rpm - does = that sound right? George (down under) That would be like disabling one of the intake valves in a 4 valve = per cylinder piston engine. Yes it will still run but the power would be = down somewhat. Just not a good idea. Tracy On Mon, Oct 12, 2009 at 4:24 PM, jrhopkins = wrote: has anyone used blocked off the center two apertures and used the = front and rear intake manifolds only? i do not understand the need for = the center split intake for aircraft use. =20 thanks Richard The center ports are smaller (the primary ports in the center iron) = are part of a system designed to use a carburetter. That means that high = velocity was needed to keep the energy high and the fuel air mixture = from forming droplets and adding to HC.=20 So the smaller barrels of the 4 barrel carb open first to operate = the engine on the high velocity runners to those ports. Most of the time = the engine ran only on those ports. So the effect is that the carb = looks small and the fuel mileage is fair, and HC (unburned Hydrocarbons) = are within requirements.=20 The key is velocity. The smaller the tube per cubic foot of mixture = per second, the higher the velocity. So the center ports and runners are = small. Since only about 20 HP is needed to go 60 MPH, most of the = engines life is run out on the small ports.=20 When more power is demanded, low manifold pressure opens the = secondaries in the carb via a vacuum diaphragm and the big ports in the = front and rear irons are called into use. The fuel economy idea is out = the window and in a properly tuned car the engine RPM will be high = enough to provide fair velocity in the big runners and ports. So the = engine will accelerate to the best power RPM (red line) to deliver the = engines rated HP. =20 In the fuel injected engine this feature is still in use so you see = the throttle bodies multiple inlets. Same idea.=20 In aircraft use, there is little use for 20 HP beyond a slow taxi. = Take off power would be everything you can come up with HP wise. So all = 4 ports and runners are needed. Once in flight, close to 50 HP would be = needed just to maintain level slow flight, so there is just no = application where the plane would fly on just the center ports. As the = plane climbs the available HP goes down based on air density changes,=20 so in most cases, the throttle is left at wide open or very close to = that. Further power reduction is by leaning to maintain the ideal fuel = air mixture, or even leaning further to well over lean, or Lean Of Peak. That is Lean Of Peak EGT (the rotary does that very well), So power = goes down as well as fuel consumption and EGT. The throttle will be left = wide open.=20 Closing off the center ports would be the same as not opening the = throttle by some amount. If you want to build in more power, the 84-85 12A has the biggest = runners and ports in the center iron. Lynn E. Hanover Warning: This e-mail transmission, and any documents, files or = previous e-mails attached to it, may contain confidential information = that is legally privileged. If you are not the intended recipient or the = person responsible for delivering it to the intended recipient, you are = hereby notified that any disclosure, copying, distribution or use of any = of the information contained in or attached to this transmission is = STRICTLY PROHIBITED. If you have received this transmission in error, = please immediately notify us by telephone at 713-662-8132 and destroy = the original transmission and its attachments without reading them. = Thank you. ------=_NextPart_000_0009_01CA4D63.C3A79000 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
 Chris,
I'm sure your right, = just=20 looking for a general indication of the secondaries coming in to = play.
 
My reason is that I was looking at a = CAD drawing=20 I did of the engine and noticed that the primaries are placed lower = than the=20 secondaries and thought they may have come in earlier. However they = come in a=20 few degree after the secondaries and close a few degrees before = the=20 secondaries.
 
My thinking is, a later opening = coupled=20 with higher velocity counters the ( any ) back 'exhaust' pressure and=20 minimizes any contamination of the incoming charge, maximizing VE at = low RPM/=20 Idle.
 
A later closing counter any possible = back=20 'compression' pressure.
 
All things being equal, the higher RPM = minimizes=20 both these situations. At higher RPM the exhaust velocity is higher = and tends=20 to be self evacuating, reducing any exhaust back pressure and might = even=20 create some vacuum, sucking some incoming charge into the exhaust.=20 The larger secondary inlet and will have a higher velocity (now) = helping=20 overcome and compression back pressure.
 
I just feel ( for my own benefit) it's = interesting to know when all this is going on - at approximately what = RPM.=20
 
I believe Tracy holds back the inlet = charge=20 timing to accommodate these changes and has the fuel injection at = the=20 optimum time - even at higher RPM I don't think he injects until the = exhaust=20 is closed. This is ideal for the larger lower velocity PP but I don't = think it=20 can be done with a carbie.
 
I mention these things for the chap = wondering=20 about the primary inlet ports.  
George ( down under)
 
George,
 
I do not believe stagging = is based on=20 RPM but instead Manifold Pressure (MP).  By default, IIRC, Tracy = has it=20 at 15.5.  Should that conflict to a cruise or often used setting, = such as=20 on final, it is pretty easily changed by selecting....I think, Mode 7, = increasing the throttle to the desired MP and then pressing the = Program button=20 when at the desired MP/RPM.  That will set it to that chosen=20 MP/RPM.  FWIW.
 
All the best,
 
Chris Barber
Houston
 
 
Cpl Christopher Barber, = JD.
Badge 330
Bellaire Police = Department
5100 Jessamine
Bellaire, Texas = 77401
 
713-668-0487
CBarber@BellariePolice.com=
From: Rotary motors in aircraft=20 [flyrotary@lancaironline.net] On Behalf Of George Lendich=20 [lendich@aanet.com.au]
Sent: Tuesday, October 13, 2009 3:48=20 PM
To: Rotary motors in aircraft
Subject: = [FlyRotary] Re:=20 intake manifold 13b 86

Lynn,
About what RPM does the secondaries = come in, if I=20 go by memory, which isn't always the best thing for mew to do, It's = about 3500=20 rpm - does that sound right?
George (down under)
That would be like disabling one of the intake valves in a 4 = valve per=20 cylinder piston engine. Yes it will still run but the power would be = down=20 somewhat.  Just not a good idea.
 
Tracy

On Mon, Oct 12, 2009 at 4:24 PM, jrhopkins = <jrhopkins@windstream.net>= =20 wrote:
has anyone used blocked off the = center two=20 apertures and used the front and rear intake manifolds only?  = i do=20 not understand the need for the center split intake for aircraft=20 use.  
 
thanks  =20 Richard
 
 
The center ports are smaller (the primary ports in the center = iron) are=20 part of a system designed to use a carburetter. That means that high = velocity was needed to keep the energy high and the fuel air = mixture=20 from forming droplets and adding to HC. 
 
So the smaller barrels of the 4 barrel carb open first to = operate the=20 engine on the high velocity runners to those ports. Most of the = time =20 the engine ran only on those ports. So the effect is that the carb = looks=20 small and the fuel mileage is fair, and HC (unburned Hydrocarbons) = are=20 within requirements. 
 
The key is velocity. The smaller the tube per cubic foot of = mixture per=20 second, the higher the velocity. So the center ports and runners are = small.=20 Since only about 20 HP is needed to go 60 MPH, most of the engines = life is=20 run out on the small ports. 
 
When more power is demanded, low manifold pressure opens the=20 secondaries in the carb via a vacuum diaphragm and the big ports in = the=20 front and rear irons are called into use. The fuel economy idea is = out the=20 window and in a properly tuned car the engine RPM will be high = enough to=20 provide fair velocity in the big runners and ports. So the engine = will=20 accelerate to the best power RPM (red line) to deliver the engines = rated=20 HP.  
 
In the fuel injected engine this feature is still in use so you = see the=20 throttle bodies  multiple inlets.
Same idea.
 
In aircraft use, there is little use for 20 HP beyond a slow = taxi. Take=20 off power would be everything you can come up with HP wise. So all 4 = ports=20 and runners are needed. Once in flight, close to 50 HP would be = needed just=20 to maintain level slow flight, so there is just no application where = the=20 plane would fly on just the center ports. As the plane climbs the = available=20 HP goes down based on air density changes,
so in most cases, the throttle is left at wide open or very = close to=20 that. Further power reduction is by leaning to maintain the ideal = fuel air=20 mixture, or even leaning further to well over lean, or Lean Of = Peak.
That is Lean Of Peak EGT (the rotary does that very well), So = power=20 goes down as well as fuel consumption and EGT. The throttle will be = left=20 wide open.
 
Closing off the center ports would be the same as not opening = the=20 throttle by some amount.
 
If you want to build in more power, the 84-85 12A has the = biggest=20 runners and ports in the center iron.
 
Lynn E. Hanover


Warning: = This=20 e-mail transmission, and any documents, files or previous e-mails = attached to=20 it, may contain confidential information that is legally privileged. = If you=20 are not the intended recipient or the person responsible for = delivering it to=20 the intended recipient, you are hereby notified that any disclosure, = copying,=20 distribution or use of any of the information contained in or attached = to this=20 transmission is STRICTLY PROHIBITED. If you have received this = transmission in=20 error, please immediately notify us by telephone at 713-662-8132 and = destroy=20 the original transmission and its attachments without reading them. = Thank=20 you.

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