X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5408495 for flyrotary@lancaironline.net; Tue, 21 Feb 2012 11:55:15 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=2.0 cv=UfLTuduN c=1 sm=0 a=g3L/TDsr+eNLfIieSKfGkw==:17 a=UVFPNn1dop8A:10 a=bJ4isTugsVYUYfvSQcYA:9 a=wPNLvfGTeEIA:10 a=glYVDZ00AAAA:8 a=Ia-xEzejAAAA:8 a=ZU3s9Sfl9G7w8jQJKmcA:9 a=M_gNzpCfUQRJZrtWtDMA:7 a=XCwpvLtFMdsA:10 a=EzXvWhQp4_cA:10 a=g3L/TDsr+eNLfIieSKfGkw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.170.10 Received: from [174.110.170.10] ([174.110.170.10:50658] helo=EdPC) by cdptpa-oedge02.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 13/7E-03352-F4CC34F4; Tue, 21 Feb 2012 16:54:39 +0000 Message-ID: From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Throttle Back Bobble Date: Tue, 21 Feb 2012 11:54:23 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000F_01CCF08F.8D9E1980" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_000F_01CCF08F.8D9E1980 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable What size throttle body do you use (diameter or type), Chris? What I would speculate (and this is all it is) is that when you = throttle down suddenly - the engine manifold pressure drops rapidly - IF = your manifold pressure sensing hoses to the EC2 are too small or there = is too much damping of the manifold pressure signal for other reasons, = then your engine could be down operating at lower manifold pressure = while your fuel injector is still calculating fuel for the higher = manifold pressure it is still seeing. So your engine could be running = overly rich for a period of time.=20 Throttling down slowly gives the manifold pressure read by the EC2 to = adjust to the engine manifold pressure as it is slowly reduced and you = avoid the mismatch due to manifold pressure differences. There could also be some mismatch between your fuel map and operational = needs. But, again these are just guesses based on the limited amount of = data. The easiest way I know to check the manifold pressure sensing = possibility is to try putting on larger manifold hoses running to the = EC2/3 or removing any damping cans or such.. Ed From: Chris Barber=20 Sent: Tuesday, February 21, 2012 10:53 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Throttle Back Bobble When I throttle back on my otherwise smooth running 13b turbo, I tend to = get a bobble (miss?) as the engine spins down. I don't seem to have it = if I throttle back very slowly and smoothly, but fast moderate (usual = manner) or quick throttle back produces it. I have noticed this on = Lycoming's if throttled back quickly, but obviously not an issue that I = have noted in a regular car engine. =20 Just curious if others have had this occur and if so why. The list has been especially quite lately so come on folks, here your = chance to shine before I start calling DAR's ;-) Chris Houston ------=_NextPart_000_000F_01CCF08F.8D9E1980 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
What size throttle body do you use (diameter or = type),=20 Chris?
 
 
What I would speculate (and this is all it is) =  is=20 that when you throttle down suddenly - the engine manifold pressure = drops=20 rapidly - IF your manifold pressure sensing hoses to the EC2 are too = small or=20 there is too much damping of the manifold pressure signal for = other=20 reasons, then your engine could be down operating at lower manifold = pressure=20 while your fuel injector is still calculating fuel for the higher = manifold=20 pressure it is still seeing.  So your engine could be running = overly rich=20 for a period of time. 
 
Throttling down slowly gives the manifold = pressure read by=20 the EC2 to adjust to the engine manifold pressure as it is slowly = reduced and=20 you avoid the mismatch due to manifold pressure = differences.
 
There could also be some mismatch between = your fuel=20 map and operational needs.  But, again these are just guesses based = on the=20 limited amount of data.
 
The easiest way I know to check the manifold = pressure=20 sensing possibility is to try putting on larger manifold hoses = running to=20 the EC2/3 or removing any damping cans or such..
 
Ed
 

From: Chris Barber
Sent: Tuesday, February 21, 2012 10:53 AM
Subject: [FlyRotary] Throttle Back Bobble

When I throttle back on my otherwise smooth=20 running 13b turbo, I tend to get a = bobble=20 (miss?) as the engine spins down.  I don't seem to have it if I = throttle=20 back very slowly and smoothly, but fast moderate (usual manner) = or quick=20 throttle back produces it.  I have noticed this=20 on Lycoming's if throttled back = quickly,=20 but obviously not an issue that I have noted in a regular = car=20 engine. 

 

Just curious if others have had this occur and if so = why.

 

The list has been especially quite lately so come on folks, here your = chance=20 to shine before I start calling DAR's = ;-)

 

Chris

Houston

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