X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 23 Mar 2009 12:59:54 -0400 Message-ID: X-Original-Return-Path: Received: from n10.bullet.re3.yahoo.com ([68.142.237.123] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with SMTP id 3556132 for lml@lancaironline.net; Mon, 23 Mar 2009 07:53:47 -0400 Received-SPF: none receiver=logan.com; client-ip=68.142.237.123; envelope-from=casey.gary@yahoo.com Received: from [68.142.237.90] by n10.bullet.re3.yahoo.com with NNFMP; 23 Mar 2009 11:53:07 -0000 Received: from [66.196.97.134] by t6.bullet.re3.yahoo.com with NNFMP; 23 Mar 2009 11:53:07 -0000 Received: from [127.0.0.1] by omp107.mail.re3.yahoo.com with NNFMP; 23 Mar 2009 11:53:07 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 58882.27721.bm@omp107.mail.re3.yahoo.com Received: (qmail 71579 invoked by uid 60001); 23 Mar 2009 11:53:06 -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=m6TLASoi9RaXmOfwAhIsNO2FzPGy6AoMV/qiE72V5OFN5pH2oeBtiJhsUja5AbJDiyXw2O7DQd7YPPt7lUxzf5rAa3IW8Ku0QiuoXuoqIdlgheYft5HaCvEt6u7O37NP0SQBT7BNP1SgrpM9MtlD0kxagvoppwVlmCiZWokqvHg=; X-Original-Message-ID: <751441.68979.qm@web57505.mail.re1.yahoo.com> X-YMail-OSG: 1yQPMY8VM1mssGF7o.KPuqXgNhugwfNP0NiSOGFkmWNClNTconEeH.RFuPDIoB4q3_kOi.rzbyLlEyfhf1neCHHEAyzs2VK34xXi7q7RLpf01V5lVVZzPmJQJk.LFgyK3Jgw4cCwmLkAPPhsSTOFtM8hHobWbqv0awBc0ALBy6uMC7kCWctDFYV2akoFRplkgVe.aEzyZKB8teLTpw-- Received: from [97.122.186.190] by web57505.mail.re1.yahoo.com via HTTP; Mon, 23 Mar 2009 04:53:06 PDT X-Mailer: YahooMailRC/1277.32 YahooMailWebService/0.7.289.1 References: X-Original-Date: Mon, 23 Mar 2009 04:53:06 -0700 (PDT) From: Gary Casey Subject: Crankcase pressurizatio X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-176117495-1237809186=:68979" --0-176117495-1237809186=:68979 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable I've been waiting for the "one best" approach to air-separation to show up,= as I would like to reduce the oil streak on my (plane's) belly, but so far= I don't see an evidence of such a thing. Some discussions have been targe= ted at "crankcase pressure" being the problem, but I don't think that has m= uch to do with anything except leakage out of various seams. Generally, bu= t not always, front crank seals won't be affected by a slight positive pres= sure as they should seal effectively with a relatively high pressure differ= ential. The crankcase pressure shouldn't be much higher than the pressure = at the vent discharge, assuming the tube diameter is relatively large (3/4 = inch or larger?). High crankcase pressure is an indicator of too much blow= by(my company builds crankcase pressure sensors used in locomotive engines = to indicate excess engine wear). Incidentally, the quantity of blowby is e= ssentially unaffected by the pressure at the vent: Remember that blowby occurs when combustion products at perhaps 800 psi leak past the ri= ngs - a change in crankcase pressure of a fraction of a psi won't change th= at flow by very much. I suspect some of the problems encountered have to d= o with the way the separator is drained. If the separator is very little h= igher than the engine drain location, the crankcase pressure doesn't have t= o be much higher than the separator pressure to prevent oil from returning = to the engine. Also, if the drain oil is led to a canister that is vented = to the engine compartment, its pressure will rise during high speed cruise,= again preventing oil from draining. The separator, if it has enough capac= ity, could just hold the oil until shutdown, after which it would drain. A= nother comment - some people are afraid to drain the recovered oil back int= o the engine and prefer to install a catch tank, saying the oil looks "bad.= " I maintain that the oil in the catch tank IS the same as the oil in the engine, so if you don't like that oil you shouldn't like the rest o= f the oil either. Actually, the reason it looks icky is that at the lower = temperature in the catch tank it tends to absorb water and will turn color.= Pour it back in the engine and the heat will drive off the water and make= it good as new.=0A=0ANote that there is little, if any data or positive st= atements in the above discussion. I would welcome a post with hard facts a= nd numbers that could lead us out of the maze. do oil separators work? No= t work? Some work and some don't? What's the difference? Does the world = need a "real" separator(I've got some ideas)? I've been listening to discu= ssions on this topic for over 20 years, though, and have yet to hear a conv= incing argument one way or the other.=0A=0AGary Casey=0A=0AFred said, in pa= rt:=0AI wrote earlier that my IO-550 was dumping oil out the air oil separa= tor, and with some fiddling with the plumbing, it appeared I solved the pro= blem. High power climbs yielded no oil loss. Ground tests showed no blow= by. Problem solved. =0A =0AWrong.=0A....=0A=0A=0A --0-176117495-1237809186=:68979 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable

I've been waiting for the "one best" approach to air-separa= tion to show up, as I would like to reduce the oil streak on my (plane's) b= elly, but so far I don't see an evidence of such a thing. =A0Some discussio= ns have been targeted at "crankcase pressure" being the problem, but I don'= t think that has much to do with anything except leakage out of various sea= ms. =A0Generally, but not always, front crank seals won't be affected by a = slight positive pressure as they should seal effectively with a relatively = high pressure differential. =A0The crankcase pressure shouldn't be much higher = than the pressure at the vent discharge, assuming the tube diameter is rela= tively large (3/4 inch or larger?). =A0High crankcase pressure is an indica= tor of too much blowby(my company builds crankcase pressure sensors used in= locomotive engines to indicate excess engine wear). =A0Incidentally, the q= uantity of blowby is essentially unaffected by the pressure at the vent: = =A0Remember that blowby occurs when combustion products at perhaps 800 psi = leak past the rings - a change in crankcase pressure of a fraction of a psi= won't change that flow by very much. =A0I suspect some of the problems enc= ountered have to do with the way the separator is drained. =A0If the separa= tor is very little higher than the engine drain location, the crankcase pre= ssure doesn't have to be much higher than the separator pressure to prevent= oil from returning to the engine. =A0Also, if the drain oil is led to a canister that is vented to the engine compartment, its pressure will rise = during high speed cruise, again preventing oil from draining. =A0The separa= tor, if it has enough capacity, could just hold the oil until shutdown, aft= er which it would drain. =A0Another comment - some people are afraid to dra= in the recovered oil back into the engine and prefer to install a catch tan= k, saying the oil looks "bad." =A0I maintain that the oil in the catch tank= IS the same as the oil in the engine, so if you don't like that oil you sh= ouldn't like the rest of the oil either. =A0Actually, the reason it looks i= cky is that at the lower temperature in the catch tank it tends to absorb w= ater and will turn color. =A0Pour it back in the engine and the heat will d= rive off the water and make it good as new.


Note that there is little, if an= y data or positive statements in the above discussion. =A0I would welcome a= post with hard facts and numbers that could lead us out of the maze. =A0do= oil separators work? =A0Not work? =A0Some work and some don't? =A0What's t= he difference? =A0Does the world need a "real" separator(I've got some idea= s)? =A0I've been listening to discussions on this topic for over 20 years, = though, and have yet to hear a convincing argument one way or the other.


Gary Casey=


=

Fred said, = in part:

I wrote earlier that my IO-550 w= as dumping oil out the air oil separator, and with some fiddling with the plumbing, it appeared I sol= ved the problem.=A0 =A0High power climbs yielded no oil loss.=A0 Ground tests sho= wed no blow by.=A0 Problem solved.=A0

Wrong.

....



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