X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-junco.atl.sa.earthlink.net ([209.86.89.63] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6623945 for lml@lancaironline.net; Tue, 03 Dec 2013 12:09:15 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.63; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=QjO2olGYTvpgIP87RLlHtoptNeiIj2ZYFRP7mhDIFId4UTz88OtN9vAsDDZOCp7m; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [72.92.128.101] (helo=[192.168.1.24]) by elasmtp-junco.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1VntSi-00027F-5x for lml@lancaironline.net; Tue, 03 Dec 2013 12:08:40 -0500 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-61--238573526 Subject: Re: [LML] Re: cabin pressure valve vs manifold pressure drop Date: Tue, 3 Dec 2013 12:08:39 -0500 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: <4D9CE94A-E0DC-4355-A969-36D61C3EC665@earthlink.net> X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9408712e7b777cbf6848fe662a5f70ea307350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 72.92.128.101 --Apple-Mail-61--238573526 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Bob, what would you expect to happen if your system had sonic nozzles on the = hot side and not on the cold, you had set the mixer to "cold" and then = you shut off cabin air? It seems to me that would result in more MP = loss than if you had it on hot. ...which leads to an observation that Craig Berland made some while = back, which is that if the cold-side cabin air plumbing is compromised = (e.g. a clamp lets loose) , you will suffer a loss of engine power. Colyn On Dec 3, 2013, at 11:54 AM, Robert R Pastusek wrote: CWFMD, =20 I=92d need more info to diagnose this completely, but write me directly = and I=92ll try to help. rpastusek@htii.com =20 Some basics on the pressurization system (applies to the IV-P with = Continental TSIO-550 engine ONLY--you didn=92t specify the = aircraft/engine): The engine is designed to =93vent=94 part of the turbocharger output = overboard during normal operation, through what are called =93sonic = nozzles=94 that basically maintain a rather constant flow rate over a = range of pressure differentials. The IV-P (and some other pressurized = Lancairs with big bore Continentals) uses this bleed air to pressurize = the cockpit. The air is routed through a mixer/control box mounted near = the top center of the firewall in the engine compartment. This = gold-colored aluminum can (about 2/3 the height of a quart oil can) has = a cockpit-controlled shuttle valve that allows selection of a mix of hot = air directly from the turbochargers and cooler air that has already = passed through the intercoolers. It also has a separate valve, with = cockpit control, that shuts off airflow to the cabin and diverts it out = the bottom of the engine compartment when cockpit pressurization (and = associated heat) is not needed. =20 As to heat, at full throttle, the turbocharger output air temperature = can be up to 300 degrees, and in the cabin heat on mode, flows pretty = directly into the cabin. With the heat control turned off, the = turbocharger air passes through a pair of air-to-air intercoolers before = heading to the cockpit for pressurization. The problem is that these = intercoolers only lower the temperature; they don=92t deliver =93cold=94 = air out the backside. When the input is at 300, the output is warm, at = best; hot in Texas in the summer. So, without air conditioning, there is = not a good source of really cool air available to pressurize the = cockpit. =20 As to the fixes: First check is to be sure the valves in the controller = are functioning as intended. Second check is to be sure you have sonic = ports installed in your turbocharger output lines that feed to this = controller. The variation you report in MP would tend to indicate there = are no sonic ports installed, and that you=92re getting =93full flow=94 = through the system, rather than restricted flow as intended=85but this = is just a guess at this point=85 not enough data. Talk or write? =20 Bob =20 From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = cwfmd@yahoo.com Sent: Tuesday, December 03, 2013 7:01 AM To: lml@lancaironline.net Subject: [LML] cabin pressure valve vs manifold pressure drop =20 We put a new canopy seal in the IV-P. I fiddled with the cabin pressure = valve to try to reduce or locate a squeal. (My Grainger smoke matches = don't light, with reduced partial pressure of Oxygen at altitude) I = noticed that pulling the cabin pressure control partially out, reduced = the cabin inflow, as expected, but also dropped the manifold pressure by = about 4 inches with a loss of about 50 hp (estimated). This was at = flight level 230. I had not previously noticed this large effect on = manifold pressure, but it could demystify performance changes in = previous data. Who knew the cabin pressure valve affected the "throttle" = setting :) It makes sense because the previous cabin pressure just dumps = overboard at the firewall. Wondering why this is set up this way.... Why = not just close the valve to the cabin, when not needed or wanted, and = leave the manifold pressure in the manifold?? In general, I noticed others have similar issues with the cost of = repair of the Dukes valve. I would rather redesign the system, using the = on-board instrumentation and computers that already know the static = pressure and the cabin pressure. I hot climates I prefer to minimize the = heat entering the cabin, and maybe just use 4-5 psi relief valves to = distribute air flow. I think my system where all the inter-cooled air = routes thru the firewall to under the back seat was designed by Eskimos, = who always need max heating. --Apple-Mail-61--238573526 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Bob,

what would you expect to = happen if your system had sonic nozzles on the hot side and not on the = cold, you had set the mixer to "cold" and then you shut off cabin air? =   It seems to me that would result in more MP loss than if you had = it on hot.

...which leads to an observation = that Craig Berland made some while back, which is that if the cold-side = cabin air plumbing is compromised (e.g. a clamp lets loose) , you will = suffer a loss of engine = power.

Colyn


On Dec 3, 2013, at 11:54 AM, Robert R Pastusek wrote:

I=92d = need more info to diagnose this completely, but write me directly and = I=92ll try to help.   
The engine is designed to =93vent=94= part of the turbocharger output overboard during normal operation, = through what are called =93sonic nozzles=94 that basically maintain a = rather constant flow rate over a range of pressure differentials. The = IV-P (and some other pressurized Lancairs with big bore Continentals) = uses this bleed air to pressurize the cockpit. The air is routed through = a mixer/control box mounted near the top center of the firewall in the = engine compartment. This gold-colored aluminum can (about 2/3 the height = of a quart oil can) has a cockpit-controlled shuttle valve that allows = selection of a mix of hot air directly from the turbochargers and cooler = air that has already passed through the intercoolers.  It also = has a separate valve, with cockpit control, that shuts off airflow to = the cabin and diverts it out the bottom of the engine compartment when = cockpit pressurization (and associated heat) is not = needed.
From: Lancair Mailing List = [mailto:lml@lancaironline.net] On Behalf Of cwfmd@yahoo.com
Sent: Tuesday, December 03, 2013 = 7:01 AM
To: lml@lancaironline.net
Subj= ect: [LML] cabin = pressure valve vs manifold pressure = drop
We put a new canopy seal in = the IV-P. I fiddled with the cabin pressure valve to try to reduce or = locate  a squeal. (My Grainger smoke matches don't light, with = reduced partial pressure of Oxygen at altitude) I noticed that pulling = the cabin pressure control partially out, reduced the cabin inflow, as = expected, but also dropped the manifold pressure by about 4 inches with = a loss of about 50 hp (estimated). This was at flight level 230. I had = not previously noticed this large effect on manifold pressure, but it = could demystify performance changes in previous data. Who knew the cabin = pressure valve affected the "throttle" setting :) It makes sense because = the previous cabin pressure just dumps overboard at the firewall. = Wondering why this is set up this way.... Why not just close the valve = to the cabin, when not needed or wanted, and leave the manifold pressure = in the manifold??