X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 22 Apr 2009 09:26:43 -0400 Message-ID: X-Original-Return-Path: Received: from n2.bullet.mail.re3.yahoo.com ([68.142.237.109] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with SMTP id 3592689 for lml@lancaironline.net; Wed, 22 Apr 2009 09:15:28 -0400 Received-SPF: none receiver=logan.com; client-ip=68.142.237.109; envelope-from=casey.gary@yahoo.com Received: from [68.142.237.88] by n2.bullet.mail.re3.yahoo.com with NNFMP; 22 Apr 2009 13:14:51 -0000 Received: from [66.196.97.134] by t4.bullet.re3.yahoo.com with NNFMP; 22 Apr 2009 13:14:51 -0000 Received: from [127.0.0.1] by omp107.mail.re3.yahoo.com with NNFMP; 22 Apr 2009 13:14:51 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 323194.87250.bm@omp107.mail.re3.yahoo.com Received: (qmail 96022 invoked by uid 60001); 22 Apr 2009 13:08:10 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=cvAvXPihGAEvuXGsDYoYxqFGe2SV7I+OV+v6AGCB+c5Ts3QkTxRXtBgnbdz/qeqG80woKW6zyCixlfOZJ393FFH3HxVFP5xSXfKjqUpV323+jf5CylVRvRgHyDFyIbNMbShSMTmr9MFLFN7zPQC1ydZ047z6c1zbpVwcPSubM9U=; X-Original-Message-ID: <207857.95961.qm@web57514.mail.re1.yahoo.com> X-YMail-OSG: IUaQM3AVM1lXnFlnzKWW5Io3uFC.7E_QMLgOUHwIGGrMvJ.dMnjuZvwp0tXanlsOFCgB9ik6_Rv4VH2rz27mhSllMCyi_EUr_fWzFYILayD61kcZ_O8WM4b3kzfiX6tXwngZ_89RuDGW5d3kfSjf85qUQlHyPFvVDBiJyqIfd79WbojOmmFO5ePC8A0El2oIMdWEbPLj__kdWJK_fPBWk8781rxWu41k1fiD6KAdxJJyseBRFGEooWk.v6XjuVFowiV3mzrnPgep7Qeiig9b55Xcnj_WymkLolEt4F5u_gsfJm55nvr8RQskZYpXCPw- Received: from [97.122.180.106] by web57514.mail.re1.yahoo.com via HTTP; Wed, 22 Apr 2009 06:08:09 PDT X-Mailer: YahooMailRC/1277.35 YahooMailWebService/0.7.289.1 References: X-Original-Date: Wed, 22 Apr 2009 06:08:09 -0700 (PDT) From: Gary Casey Subject: Re: Ram Air Design X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-849515120-1240405689=:95961" --0-849515120-1240405689=:95961 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Why would the addition of the "trim rings" change the air flow? I assume b= ecause the inlet area is reduced if only slightly and more likely that the = smooth airflow is "tripped" by the sharp edges. In my opinion, the "ram ai= r" (quotes used deliberately) tube that is on most Continental-engined Lanc= airs is the worst I have ever seen. The tubing is large enough - probably = too large, but the sharp leading edge probably destroys any potential for p= ressure recovery. And with it extending significantly into the cooling air= inlet, those same sharp edges have to reduce cooling air flow. What to do= ? One of my favorites is to just put another air filter on the second inle= t pipe and get rid of the mechanisms in the inlet system - they worry me an= yway, as the small bits can come loose and go through the engine while the = big pieces can come loose and block the air flow completely. Use the highe= r pressure in the upper cooling plenum to give most of the pressure recovery that is possible - probably 75%. What do you do about an alterna= te air source? Maybe nothing, as half of the filter area is pointing backw= ards and won't be plugged with snow anyway. Or just through away that pret= ty "filter" and put hardware cloth over the inlet. My feelings about the e= ffectiveness of K&N filters might be showing, I suppose. At the very least= just cut off the ram air tube and put a bell-shaped entrance on it. Your = idea of extending the inlet forward is good, but as Grayhawk said, to be mo= st effective it has to be away from the hub. This is because the round pro= peller sections near the hub are just obstructions to air flow. I put my c= hin inlet (bottom-inlet Lycoming engine) close to the hub and it was a mist= ake, but I don't think it hurts a lot. Take a look at some of the turbo 21= 0's - they have a separate ram air inlet on the outboard edge of the coolin= g inlet and they have a rounded leading edge. But for your installation how do you move it away? I'm not sure, but I know what I wou= ld do - use two rectangular paper filters with a smooth transition from the= re to the throttle body. Simple, works good, lasts a long time. It would = lose maybe 10% of what ram air could be obtained by heroic efforts, but a 1= 0% loss in ram pressure probably represents 1% in power, or 0.3% in max spe= ed. And the extra air filter area would probably give 1% more power at tak= eoff and reduce the amount of dust by 90% compared to the K&N solution. FW= IW=0A=0AGary Casey=0AES, Lycoming engine, paper filter from a turbo 402 Ces= sna.=0A=0A=0A=0A=0A=0A________________________________=0A=0A=0A=0APosted fo= r "Douglas Brunner"=0A:=0A=0A Recently, I ins= talled two aluminum cowl inlets (see photo) in my Legacy. I =0Adid this=0A= largely for aesthetic reasons, but also expected that it would =0Aimprove m= y ram air pressure. I was wrong - for reasons I don't=0Aunderstand my =0Ar= am air MP is now less that my filtered air MP by a full inch. (My ram air = is =0Areversed because my plane had de-ice=0Aand the de-ice alternator is o= n the left =0Aside).=0A =0A I have sketched a new ram air system that I hop= e will give me back at least =0A1.5 or 2 inches of ram air. (see sketch). = Features:=0A 1.. The ram air inlet will be flush with the cowl inlet and w= ell out into =0Athe air stream.=0A 2.. A "flapper valve" to block the filt= er when not in use=0A Your thoughts?=0A =0A Any suggestions of=0Awho could = fabricate this? =0A=0A=0A --0-849515120-1240405689=:95961 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Why would the addition of the "trim rings" change = the air flow? =A0I assume because the inlet area is reduced if only slightl= y and more likely that the smooth airflow is "tripped" by the sharp edges. = =A0In my opinion, the "ram air" (quotes used deliberately) tube that is on = most Continental-engined Lancairs is the worst I have ever seen. =A0The tub= ing is large enough - probably too large, but the sharp leading edge probab= ly destroys any potential for pressure recovery. =A0And with it extending s= ignificantly into the cooling air inlet, those same sharp edges have to red= uce cooling air flow. =A0What to do? =A0One of my favorites is to just put = another air filter on the second inlet pipe and get rid of the mechanisms i= n the inlet system - they worry me anyway, as the small bits can come loose and go through the engine while the big pieces can come loose and block th= e air flow completely. =A0Use the higher pressure in the upper cooling plen= um to give most of the pressure recovery that is possible - probably 75%. = =A0What do you do about an alternate air source? =A0Maybe nothing, as half = of the filter area is pointing backwards and won't be plugged with snow any= way. =A0Or just through away that pretty "filter" and put hardware cloth ov= er the inlet. =A0My feelings about the effectiveness of K&N filters mig= ht be showing, I suppose. =A0At the very least just cut off the ram air tub= e and put a bell-shaped entrance on it. =A0Your idea of extending the inlet= forward is good, but as Grayhawk said, to be most effective it has to be a= way from the hub. =A0This is because the round propeller sections near the = hub are just obstructions to air flow. =A0I put my chin inlet (bottom-inlet= Lycoming engine) close to the hub and it was a mistake, but I don't think = it hurts a lot. =A0Take a look at some of the turbo 210's - they have a separ= ate ram air inlet on the outboard edge of the cooling inlet and they have a= rounded leading edge. =A0But for your installation how do you move it away= ? =A0I'm not sure, but I know what I would do - use two rectangular paper f= ilters with a smooth transition from there to the throttle body. =A0Simple,= works good, lasts a long time. =A0It would lose maybe 10% of what ram air = could be obtained by heroic efforts, but a 10% loss in ram pressure probabl= y represents 1% in power, or 0.3% in max speed. =A0And the extra air filter= area would probably give 1% more power at takeoff and reduce the amount of= dust by 90% compared to the K&N solution. =A0FWIW

=
Gary Casey
ES, Lycoming engine, paper filter from a turbo 40= 2 Cessna.





Posted for "Douglas Brunner"=0A<douglasbrunner@earthlink.net>:
<= br>=A0Recently, I installed two aluminum cowl inlets (see photo) in my Lega= cy.=A0=A0I
did this=0Alargely for aesthetic reasons, but also expected = that it would
improve my ram air pressure.=A0=A0I was wrong - for reaso= ns I don't=0Aunderstand my
ram air MP is now less that my filtered air = MP by a full inch.=A0=A0(My ram air is
reversed because my plane had de= -ice=0Aand the de-ice alternator is on the left
side).
=A0
=A0I h= ave sketched a new ram air system that I hope will give me back at least=0A=
1.5 or 2 inches of ram air. (see sketch).=A0=A0Features:
=A0 1.. The= ram air inlet will be flush with the cowl inlet and well out into=0A
th= e air stream.
=A0 2.. A "flapper valve" to block the filter when not in = use
=A0Your thoughts?
=A0
=A0Any suggestions of=0Awho could fabric= ate this?=A0=A0
=0A


=0A=0A --0-849515120-1240405689=:95961--