Return-Path: <13brv3@bellsouth.net> Received: from imf21aec.mail.bellsouth.net ([205.152.59.69] verified) by logan.com (CommuniGate Pro SMTP 4.2b1) with ESMTP id 3136817 for flyrotary@lancaironline.net; Tue, 30 Mar 2004 12:31:39 -0500 Received: from rad ([65.0.151.4]) by imf21aec.mail.bellsouth.net (InterMail vM.5.01.06.08 201-253-122-130-108-20031117) with ESMTP id <20040330173138.VRUO1763.imf21aec.mail.bellsouth.net@rad> for ; Tue, 30 Mar 2004 12:31:38 -0500 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: No rev-2 flying yet (Tracy, see comments in red) Date: Tue, 30 Mar 2004 11:33:42 -0600 Message-ID: <001b01c4167d$25e7d550$6001a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001C_01C4164A.DB4D6550" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 In-Reply-To: Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_001C_01C4164A.DB4D6550 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable My guess is that it appears that when closing the throttle very = rapidly, you probably end up with an overly rich intake manifold air/fuel = mixture. This may occur because in one fraction of a second you are opearting at = WOT (lots of fuel flow) and the next down to idle. So the rpm drops down = in to the LOW, LOW range due to the rapid decrease in manifold pressure caused = by the rapid throttle closure and still rapidly pumping rotors. So its = down in the low rpm range with a rich mixture and then since the rpm is so low, = the manifold pressure may well creeep back up to the 16-17" Hg range simple because there is not enough rpm to keep the manifold pressure lower. = So now the system is seeing higher manifold pressure. Since the system = only really uses the manifold pressure (and not rpm) in its calculation, the higher manifold pressure convinces itself that you have opened the = throttle a bit (while you actually have not) and so it dumps in a bit more fuel. = This keeps the mixture overly rich as there is really not as much air coming = into the system. Once you crack the throttle a bit, more air flow leans out = the mixture, rpm increases, manifold pressure actually decrease back to = 14-15" Hg and the system stabilizes.=20 =20 GREAT explanation!!! That's got to be exactly what's happening. =20 Thanks, Rusty (now I can ignore that "problem")=20 ------=_NextPart_000_001C_01C4164A.DB4D6550 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
My guess is that it  appears = that when=20 closing the throttle very rapidly, you probably end up with an overly =  rich=20 intake manifold air/fuel mixture.  This may occur because in = one=20 fraction of a second you are  opearting at WOT (lots of fuel = flow)=20  and the next down to idle.  So the rpm drops down in to the = LOW, LOW=20 range due to the rapid decrease in manifold pressure caused by the rapid = throttle closure and still rapidly pumping rotors.  So its = down in the=20 low rpm range with a rich mixture and then since the rpm is so = low,  the=20 manifold pressure may well creeep back up to the 16-17" Hg range simple = because=20 there is  not enough rpm to keep the manifold pressure = lower.  So=20 now the system is seeing   higher manifold pressure.  = Since the=20 system only really uses the manifold pressure (and not rpm) in its = calculation,=20 the higher manifold pressure convinces itself that  you have opened = the=20 throttle a bit (while you actually have not) and so it dumps in a = bit more=20 fuel. This keeps the mixture overly rich as there is really = not as=20 much air coming into the system.  Once you crack the throttle a = bit, more=20 air flow leans out the mixture, rpm increases, manifold pressure = actually=20 decrease back to 14-15" Hg and the system stabilizes. 
 
GREAT=20 explanation!!!  That's got to be exactly what's=20 happening.
 
Thanks,
Rusty (now=20 I can ignore that=20 "problem") 
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