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 5409941 for flyrotary@lancaironline.net; Wed, 22 Feb 2012 09:51:32 -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=FOSZNpUs c=1 sm=0 a=g3L/TDsr+eNLfIieSKfGkw==:17 a=AHkS0RJitIMA:10 a=wMCNeaCvj-4A:10 a=ayC55rCoAAAA:8 a=Vu50oLefazSOA1WbNfwA:9 a=vh7TqWOq8tesU02e2AEA:7 a=wPNLvfGTeEIA:10 a=glYVDZ00AAAA:8 a=Ia-xEzejAAAA:8 a=rG4PzXEhwenN60GQaDcA:9 a=TFvrRG-oPkwN09vwnqMA: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] ([174.110.170.10:54675] helo=EdPC) by cdptpa-oedge02.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id D5/4C-21438-1D0054F4; Wed, 22 Feb 2012 14:50:57 +0000 Message-ID: From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: Throttle Back Bobble Date: Wed, 22 Feb 2012 09:50:56 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01CCF147.78F42520" 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_000C_01CCF147.78F42520 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ok, 3" would not likely be causing this problem. =20 It may not be a restrictive manifold pressure sensing line - but, if its = easy enough to take the restrictive plug out of the line, I would give = that a try. Some folks put a restriction in to damp or smooth out the manifold = pressure pulses - but, if too restrictive can delay the EC2 response to = manifold pressure changes. Ed From: Chris Barber=20 Sent: Wednesday, February 22, 2012 8:37 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: Throttle Back Bobble Ed,=20 I have the Mistral intake. I do think we put a restrictive plug in the = pressure line. Not sure why we decided on this as it was, IIRC, = recommended by a buddy that was formerly very involved in the project. I = will check tonight if I make it out to the hangar.=20 I am not sure what the diameter, however, I think the turbo duct to it = is three inches.=20 Thanks.=20 Chris.=20 Sent from my iPhone 4 On Feb 21, 2012, at 10:54 AM, "Ed Anderson" = wrote: 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_000C_01CCF147.78F42520 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ok, 3" would not likely be causing this = problem. =20
 
It may not be a restrictive manifold pressure = sensing line=20 - but, if its easy enough to take the restrictive plug out of the = line, I=20 would give that a try.
 
Some folks put a restriction in to damp or = smooth out the=20 manifold pressure pulses - but, if too restrictive can delay the EC2 = response to=20  manifold pressure changes.
 
Ed

From: Chris Barber
Sent: Wednesday, February 22, 2012 8:37 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: Throttle Back = Bobble

Ed, 

I have the Mistral intake. I do think we put a restrictive plug in = the=20 pressure line. Not sure why we decided on this as it was, IIRC, = recommended by a=20 buddy that was formerly very involved in the project. I will check = tonight if I=20 make it out to the hangar. 

I am not sure what the diameter, however, I think the turbo duct to = it is=20 three inches. 

Thanks. 

Chris. 

Sent from my iPhone 4

On Feb 21, 2012, at 10:54 AM, "Ed Anderson" <eanderson@carolina.rr.com&g= t;=20 wrote:

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=20 by the EC2 to adjust to the engine manifold pressure as it is slowly = reduced=20 and 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=20 the 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=20 quick 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=20 chance to shine before I start = calling DAR's=20 ;-)

 

Chris

Houston

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