X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 15 Dec 2007 08:59:31 -0500 Message-ID: X-Original-Return-Path: Received: from mail02.syd.optusnet.com.au ([211.29.132.183] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTPS id 2581703 for lml@lancaironline.net; Fri, 14 Dec 2007 19:42:44 -0500 Received-SPF: pass receiver=logan.com; client-ip=211.29.132.183; envelope-from=fredmoreno@optusnet.com.au Received: from fred ([202.139.5.198]) (authenticated sender fredmoreno) by mail02.syd.optusnet.com.au (8.13.1/8.13.1) with ESMTP id lBF0fgoP025243 for ; Sat, 15 Dec 2007 11:41:52 +1100 From: "Fred Moreno" X-Original-To: "Lancair Mail" Subject: GAMI Injectors - More questions for Walter X-Original-Date: Sat, 15 Dec 2007 09:41:37 +0900 X-Original-Message-ID: <00ec01c83eb3$4811e6e0$c6058bca@fred> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00ED_01C83EFE.B7F98EE0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6822 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 Importance: Normal Thread-Index: Acg+QRI2yTLEuPgFS4aIu87GyxGgQgAa5oJA This is a multi-part message in MIME format. ------=_NextPart_000_00ED_01C83EFE.B7F98EE0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Many thanks to all that responded to my post. The discussion is most enlightening. And there is nothing like actual operational experience = to correct nebulous speculations. Thanks also to Walter who pointed out my fuzzy thinking that was blending atomization and vaporization. They are separate processes. =20 More questions:=20 =20 =20 1) The turbo injectors do not have screens like the NA injectors do. = They have air inlets from an upper deck reference line. Scott is using = those. =20 Do the turbo injectors have better air passages that allow them to do a better atomization job than the normally aspirated injectors, even when installed in a normally aspirated engine? Said another way, for the = same delta P do the screens on the NA injectors restrict air flow compared to = the turbo injectors with their air shroud and supply line? =20 2) The delta air pressure is most important at WOT... A delta P of 3" = Hg is adequate to result in excellent fuel atomization to aid in vaporization. More pressure does not necessarily make things better. =20 OK, let's see what might be possible with a normally aspirated engine. = The ram pressure at 200 KIAS is about 2 inches Hg, give or take. Let's = assume you get 100% of this for the fuel injector air flow using a nice pitot = tube set up like Scott's. And let's assume that the engine induction system = gets about 75% of this for a little manifold pressure boost at WOT, this = being a typical figure for a good diffuser taking in induction air. Then the difference of 0.5 inch Hg is available for atomization. This is clearly better than zero, but a lot less than 3" Hg. So might one make further improvements in atomization by somehow boosting the injector air flow? = (The mind boggles..) Or is 0.5 inches Hg enough at WOT cruise? =20 3) Mark wrote: I cobbled together a similar arrangement to supply ram = air to the injector shrouds. I can't say I see a bunch of speed improvement as = I'm not one for careful analytical testing. I can say - the improvement in engine smoothness when running LOP in high altitude cruise is DRAMATIC. =20 Please tell us more about your set up, Mark. Is your engine induction = air coming from a separate scoop than the cooling air? Does your cooling = air come through small inlet ports in the cowl? Which engine? =20 Here is why I ask. If you have a good induction air inlet that is = getting a high percentage of the ram air pressure, and smaller cooling air inlet = ports that do a lesser job at recovering the ram pressure, then it is entirely possible that your manifold pressure is higher than the cooling air = pressure surrounding the normally aspirated injectors. =20 =20 This "reverse pressure delta P" would reverse the injector air flow, and = may cause the blue staining that was mentioned around the NA injectors. It would also cause poor atomization that becomes most evident operating = LOP. =20 =20 But if you now add a pitot set up like Scott's, you get more air = pressure fed to the injectors, and you restore the injector air flow to the way = it should be - air flowing into the intake manifold instead of out of it. Atomization improves and your ability to lean further improves as a = result. Do you think that may have been happening on your plane? =20 The reason I persist on this topic is that for those of us using = IO-550's in Legacy or ES (or rare birds like me, in an LIV) where induction air is coming from inside the cowl, there may be a lot to learn that could = improve our cruise efficiency, particularly worthwhile with 5 buck avgas.=20 =20 =20 I see another test program looming on the horizon... =20 =20 Still Curious Fred ------=_NextPart_000_00ED_01C83EFE.B7F98EE0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Many thanks to all that responded = to my post.  The discussion is most enlightening.  And there is = nothing like actual operational experience to correct nebulous = speculations.  Thanks also to Walter who pointed out my fuzzy thinking that was blending = atomization and vaporization.  They are separate processes.

 

More questions:

 

 

1)  The turbo injectors do = not have screens like the NA injectors do.  They have air inlets from an = upper deck reference line.  Scott is using those.

 

Do the turbo injectors have better = air passages that allow them to do a better atomization job than the = normally aspirated injectors, even when installed in a normally aspirated = engine?  Said another way, for the same delta P do the screens on the NA = injectors restrict air flow compared to the turbo injectors with their air shroud = and supply line?

 

2) The delta air pressure is most = important at WOT...  A delta P of 3" Hg is adequate to result in = excellent fuel atomization to aid in vaporization.  More pressure does not = necessarily make things better.

 

OK, let’s see what might be = possible with a normally aspirated engine.  The ram pressure at 200 KIAS is = about 2 inches Hg, give or take.  Let’s assume you get 100% of this = for the fuel injector air flow using a nice pitot tube set up like = Scott’s.  And let’s assume that the engine induction system gets about 75% = of this for a little manifold pressure boost at WOT, this being a typical figure = for a good diffuser taking in induction air.  Then the difference of 0.5 = inch Hg is available for atomization.  This is clearly better than zero, = but a lot less than 3” Hg.  So might one make further improvements in atomization by somehow boosting the injector air flow?  (The mind = boggles….)  Or is 0.5 inches Hg enough at WOT cruise?

 

3) Mark wrote: I cobbled together a similar arrangement to supply ram air = to the injector shrouds. I can't say I see a bunch of speed improvement as I'm not = one for careful analytical testing.  I can say - the improvement in engine smoothness when running LOP in high altitude cruise is = DRAMATIC.

 

Please tell us more about your set = up, Mark.  Is your engine induction air coming from a separate scoop = than the cooling air?  Does your cooling air come through small inlet ports = in the cowl?  Which engine?

 

Here is why I ask.  If you = have a good induction air inlet that is getting a high percentage of the = ram air pressure, and smaller cooling air inlet ports that do a = lesser job at recovering the ram pressure, then it is entirely possible that your = manifold pressure is higher than the cooling air pressure surrounding the = normally aspirated injectors. 

 

This “reverse pressure delta = P” would reverse the injector air flow, and may cause the blue staining = that was mentioned around the NA injectors.  It would also cause poor = atomization that becomes most evident operating LOP. 

 

But if you now add a pitot set up = like Scott’s, you get more air pressure fed to the injectors, and you = restore the injector air flow to the way it should be – air flowing into = the intake manifold instead of out of it.  Atomization improves and = your ability to lean further improves as a result.  Do you think that = may have been happening on your plane?

 

The reason I persist on this topic = is that for those of us using IO-550’s in Legacy or ES (or rare birds like = me, in an LIV) where induction air is coming from inside the cowl, there = may be a lot to learn that could improve our cruise efficiency, particularly = worthwhile with 5 buck avgas.

 

 

I see another test program looming = on the horizon…..

 

 

Still Curious = Fred

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