Return-Path: Received: from [65.54.169.98] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.2b2) with ESMTP id 3208177 for flyrotary@lancaironline.net; Thu, 06 May 2004 00:38:28 -0400 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Wed, 5 May 2004 21:38:29 -0700 Received: from 4.174.2.185 by bay3-dav68.adinternal.hotmail.com with DAV; Thu, 06 May 2004 04:38:28 +0000 X-Originating-IP: [4.174.2.185] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: [FlyRotary] Date: Thu, 6 May 2004 00:38:23 -0400 MIME-Version: 1.0 X-Mailer: MSN Explorer 7.02.0011.2700 Content-Type: multipart/alternative; boundary="----=_NextPart_001_0002_01C43302.700FC790" Message-ID: X-OriginalArrivalTime: 06 May 2004 04:38:29.0013 (UTC) FILETIME=[FA578C50:01C43323] ------=_NextPart_001_0002_01C43302.700FC790 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable ----- Original Message ----- From: Al Gietzen Sent: Thursday, May 06, 2004 12:19 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: [FlyRotary] Subject: [FlyRotary] Re: [FlyRotary] Dave, It sounds like you have a lean surge region. Engine will drop down in = rpm to where the fuel Map provides ample fuel, the engine produces more powe= r and starts to accelerate and at some higher rpm enters a region of insufficient fuel delivery where the engine can not maintain that rpm and starts to decrease. As the engine drops in rpm it again encounters a reg= ion where sufficient fuel exists and starts to accelerate again, repeats, etc= OK, this I understand. Here is what I believe is happening. In my case, When the engine is both low in rpm and low in manifold pressure (15" or below) the idle is fine. However, if I lower the engine rpm even more the manifold pressure actual= ly starts to increase (may go over 17"). =20 This I don=E2=80=99t understand. =20 Tracy's EC2 actually computes the fuel injector pulse duration based on manifold pressure sensed (RPM simpl= y determines the rate that the injectors are triggered). So as the engine rpm is lowered (it should require less fuel). But, past a certain point lowering the rpm causes the manifold pressure to start to increase (engin= e speed is simply not sufficient to maintain the lower manifold pressure) =20 Normally one would decrease rpm by further lowering the MAP by further cl= osing of the throttle plate. Do you mean you reduce the rpm by some mean= s other than decreasing manifold pressure? Like changing the mixture? when that happens the EC2 senses that INCREASE in manifold pressure and treats the increase as a demand for more fuel when in reality the new lower rpm requires proportionately less fuel. This gives you an overly rich condit= ion so you reduce the air/fuel ratio with you mixture knob. When you do that you reduce the mixture sufficiently from the overly rich side to cause th= e engine to increase in rpm this may cause the manifold pressure to actuall= y decrease (goes say from 17" to 15" as the rpm picks up a bit). Manifold pressure decrease causes less fuel to be injected causing a lean region a= nd engine dies back in rpm, etc.. After sufficient leaning, I was able to get my engine to run OK on the dy= no at low rpm with the 550cc/min injectors (primary in the housing); with= fixed 40psi fuel pressure. The issue I couldn=E2=80=99t resolve was the= =E2=80=98overshoot=E2=80=99 =E2=80=93 decelerating from a higher rpm and= MAP going to a level below where I could make an adjustment =E2=80=93 re= sulting in the engine dying. The EM-2 is going to allow me to resolve th= at; right? Al Can't say for sure but my guess is that this situation will probably neve= r occur, given the load characteristics on an operational airplane. Or = it might. When you suddenly decelerate, the manifold pressure and requir= ed injector pulse width may go below the point where those big injectors = can accurately meter the proper fuel batch. If you lower the fuel pressu= re and the problem gets better or goes away, that is a good indication th= at the injectors are operating below their minimum pulse width. =20 Tracy ------=_NextPart_001_0002_01C43302.700FC790 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
 
<= DIV> 
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----- Original Message -----
From: Al Gietzen
Sent: Thursday,= May 06, 2004 12:19 AM
To: R= otary motors in aircraft
Subject= : [FlyRotary] Re: [FlyRotary]
 

 

Subject: [FlyRotary] Re: [FlyRo= tary]

 

Da= ve,

 

&n= bsp; It sounds like you have a lean surge region.  Engine will drop = down in rpm

to where  the fuel Map pro= vides ample fuel, the engine produces more power

and starts to accelerate and at some higher rpm enters a region of<= /SPAN>

insufficient fuel delivery where the engine= can not maintain that rpm and

= starts to de= crease.  As the engine drops in rpm it again encounters a region

where sufficient fuel exists and starts to acc= elerate again, repeats, etc.

 

OK, this I understand=

=  

Here= is what I believe is happening.  In my case, When the engine is bot= h

= low in rpm and low in manifold pressure (= 15" or below) the idle is fine.

However, if= I lower the engine rpm even more the manifold pressure actually

starts to increase (may go over 17").  =

 

= This I don=E2=80=99t understand.

 

Tracy's EC2 actually = computes the

fuel injector pulse duration based on manifo= ld pressure sensed (RPM simply

= determines t= he rate that the  injectors are triggered).  So as the engine

rpm is lowered (it should require less fuel)=   But, past a certain point

lowering = the rpm causes the manifold pressure to start to increase (engine<= /FONT>

speed is simply not sufficient to maintain the low= er manifold pressure)

 =

<= SPAN style=3D"FONT-SIZE: 11pt; COLOR: blue; FONT-FAMILY: Verdana">Normall= y one would decrease rpm by further lowering the MAP by further closing o= f the throttle plate.  Do you mean you reduce the rpm by some means = other than decreasing manifold pressure?  Li= ke changing the mixture?

when=

that happens the EC2 senses that INCREASE in manifold pr= essure and treats

the increase as a demand = for more fuel when in reality the new lower rpm

requires proportionately less fuel.  This gives you an overly r= ich condition

so you reduce the air/fuel ra= tio with you mixture knob.  When you do that

you reduce the mixture sufficiently from the overly rich side to c= ause the

engine to increase in rpm this may= cause the manifold pressure to actually

de= crease (goes say from 17" to 15" as the rpm picks up a bit).  Manifo= ld

pressure decrease causes less fuel to be= injected causing a lean region and

engine = dies back in rpm, etc..

 

After sufficient leaning, I was able to get my engine= to run OK on the dyno at low rpm with the 550cc/min injectors (primary i= n the housing); with fixed 40psi fuel pressure.  The issue I couldn=E2= =80=99t resolve was the =E2=80=98overshoot=E2=80=99 =E2=80=93 deceleratin= g from a higher rpm and MAP going to a level below where I could make an = adjustment =E2=80=93 resulting in the engine dying.  The EM-2 is goi= ng to allow me to resolve that; right?

 

Al

=  

 

 

Can't say for sure but my guess is that this situa= tion will probably never occur, given the load characteristics on an= operational  airplane.  Or it might.  When you suddenly d= ecelerate, the manifold pressure and required injector pulse width may go= below the point where those big injectors can accurately meter the prope= r fuel batch.  If you lower the fuel pressure and the problem gets b= etter or goes away, that is a good indication that the injectors are oper= ating below their minimum pulse width. 

 =

Trac= y

 

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