X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [64.129.170.194] (HELO VIRCOM1.fcdata.private) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5409805 for flyrotary@lancaironline.net; Wed, 22 Feb 2012 08:38:17 -0500 Received-SPF: none receiver=logan.com; client-ip=64.129.170.194; envelope-from=cbarber@texasattorney.net Received: from FCD-MAIL06.FCDATA.PRIVATE (unverified [172.16.5.23]) by VIRCOM1.fcdata.private (Vircom SMTPRS 5.1.1024.13396) with ESMTP id for ; Wed, 22 Feb 2012 07:37:29 -0600 X-Modus-BlackList: 172.16.5.23=OK;cbarber@texasattorney.net=OK X-Modus-RBL: 172.16.5.23=Excluded X-Modus-Trusted: 172.16.5.23=NO X-Modus-Audit: FALSE;0;0;0 Received: from FCD-MAIL05.FCDATA.PRIVATE ([fe80::809d:a06e:5913:452e]) by FCD-MAIL06.FCDATA.PRIVATE ([fe80::697f:d6aa:b87:78d8%17]) with mapi id 14.01.0355.002; Wed, 22 Feb 2012 07:37:40 -0600 From: Chris Barber To: Rotary motors in aircraft CC: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Throttle Back Bobble Thread-Topic: [FlyRotary] Re: Throttle Back Bobble Thread-Index: AQHM8Lma/x+UpZ8FvkWnP9TRAA3g6pZI7Kls Date: Wed, 22 Feb 2012 13:37:40 +0000 Message-ID: <9C3E146D-3F31-4A2B-A054-14DECFA71142@texasattorney.net> References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Content-Type: multipart/alternative; boundary="_000_9C3E146D3F314A2BA05414DECFA71142texasattorneynet_" MIME-Version: 1.0 --_000_9C3E146D3F314A2BA05414DECFA71142texasattorneynet_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Ed, I have the Mistral intake. I do think we put a restrictive plug in the pres= sure 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 tonigh= t if I make it out to the hangar. I am not sure what the diameter, however, I think the turbo duct to it is t= hree inches. Thanks. Chris. 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 d= own suddenly - the engine manifold pressure drops rapidly - IF your manifol= d pressure sensing hoses to the EC2 are too small or there is too much damp= ing of the manifold pressure signal for other reasons, then your engine cou= ld 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. Throttling down slowly gives the manifold pressure read by the EC2 to adjus= t 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 nee= ds. 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 i= s to try putting on larger manifold hoses running to the EC2/3 or removing = any damping cans or such.. Ed From: Chris Barber Sent: Tuesday, February 21, 2012 10:53 AM To: Rotary motors in aircraft Subject: [FlyRotary] Throttle Back Bobble When I throttle back on my otherwise smooth running 13b turbo, I tend to ge= t 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 thr= ottled back quickly, but obviously not an issue that I have noted in a regu= lar car 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 chanc= e to shine before I start calling DAR's ;-) Chris Houston --_000_9C3E146D3F314A2BA05414DECFA71142texasattorneynet_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
Ed, 

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, recommende= d by a buddy that was formerly very involved in the project. I will check t= onight if I make it out to the hangar. 

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

Thanks. 

Chris. 

Sent from my iPhone 4

On Feb 21, 2012, at 10:54 AM, "Ed Anderson" <eanderson@carolina.rr.com> wrote:

What size throttle body do you use (diameter or t= ype), Chris?
 
 
What I would speculate (and this is all it is) &n= bsp;is that when you throttle down suddenly - the engine manifold pres= sure 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 cou= ld 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. 
 
Throttling down slowly gives the manifold pressur= e 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 yo= ur 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 pres= sure sensing possibility is to try putting on larger manifold hoses ru= nning to the EC2/3 or removing any damping cans or such..
 
Ed
 

Sent: Tuesday, February 21, 2012 10:53 AM
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 smoo= thly, but fast moderate (usual manner) or quick throttle back produces it.  I have noticed this on Lyco= ming's if throttled back quickly, but = ;obviously not an issue that I have noted in a regular car engine.&n= bsp;

 

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 ch= ance to shine before I start calling DAR's= ;-)

 

Chris

Houston

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