X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3746437 for flyrotary@lancaironline.net; Mon, 06 Jul 2009 10:25:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.123; envelope-from=eanderson@carolina.rr.com Received: from computername ([75.191.186.236]) by cdptpa-omta04.mail.rr.com with ESMTP id <20090706142439946.VQFY2041@cdptpa-omta04.mail.rr.com> for ; Mon, 6 Jul 2009 14:24:39 +0000 From: "Ed Anderson" To: "'Rotary motors in aircraft'" Subject: Potential Low range MCT (MAP) Problem on EC3/Ec2 Date: Mon, 6 Jul 2009 10:24:45 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002E_01C9FE23.FBEB92C0" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Thread-Index: Acn+RYKwDgVUvGcTR2OfJ9S0qHMwWg== Message-Id: <20090706142439946.VQFY2041@cdptpa-omta04.mail.rr.com> This is a multi-part message in MIME format. ------=_NextPart_000_002E_01C9FE23.FBEB92C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I happened to be reading the EC3 operating manual =96 doesn=92t everyone = do this for pleasure reading{:>)? When I came across something that may explain something that Joe and I observed (and may have played a role in the = hard to start problem we initially encountered (after the CAS wiring problem was fixed) =20 Joe has the later version of the EC2 where the lower rpm operating of = the fuel MAP (or more correctly the MCT - Map Correction Table), where the common assumption/understanding is that the operating point below 2300 = rpm is based solely on rpm. Turn=92s out that assumption is not quite = correct per this extract from the EC3 manual. =20 EC3 Mixture Correction Table addressing is illustrated on the = following page. Note that below 2300 rpm and 13=94 manifold pressure (absolute), = the MCT address is a function of rpm as opposed to manifold pressure. If = you have an EM2 engine monitor to display the data, you can use a copy of = this chart to record your table data after the engine is tuned =20 =20 Not that there are two conditions that must be met before the EC3/EC2 = uses only rpm to determine the lower operating point. The engine rpm must be below 2300 AND the manifold pressure must be below 13=94 Hg. So that = implies that if you are operating at 2000 rpm, but your manifold pressure is at = 13.5 or 14 or higher then the EC2 is using the manifold pressure to determine = the operating point and not the rpm. =20 So lets say you are trying to start your engine =96 rpm < 2300 but = manifold pressure > 13. Therefore the MCT pointer may be pointing to the bin corresponding to a manifold pressure that is close to ambient (29.92=94 = Hg). That is also the point for WOT throttle (Lots of fuel). So its safe to = say that on the first turn of the prop that is where your Ec3/2 is at. The instance the engine fires, the manifold pressure immediately begins to = drop =96 how fast it drops will depend in part on what throttle setting you = have. If you throttle is closed, the manifold pressure will almost immediately drop to low values (presumably below 13=94 hg) and all is well. If = however, your throttle is set at =BC or more open, then the manifold pressure is = not as likely to drop below 13=94 hg. If this is the case, then the operating = point is going to be based on manifold pressure which may be considerably = above 13=94 Hg. That point in turn may be overly rich for idle conditions and = your engine fails to sustain operation do to excess fuel and floods. =20 Tracy, of course, may have algorithms to deal with this, but based = solely on the comments in the manual =96 looks like this could happen. = Particularly in the early stages, before you get the MCT tuned. =20 Thought I would pass this on =96 my older EC2 only uses manifold = pressure across the entire range. =20 Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm =20 =20 ------=_NextPart_000_002E_01C9FE23.FBEB92C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

I happened to be reading the EC3 operating manual = – doesn’t everyone do this for pleasure reading{:>)? When I came = across something that may explain something that Joe and I observed (and may = have played a role in the hard to start problem we initially encountered = (after the CAS wiring problem was fixed)

 

Joe has the later version of the EC2 where the lower = rpm operating of the fuel MAP =A0(or more correctly the MCT - Map Correction = Table), where the common assumption/understanding =A0is that the operating point below 2300 rpm is based = solely on rpm.=A0 Turn’s out that assumption =A0is not quite correct per this = extract from the EC3 manual.

 

EC3=A0 Mixture = Correction Table addressing=A0 is illustrated on the following page.=A0 Note that = below 2300 rpm = and = 13” manifold = pressure (absolute), the MCT address is = a function of rpm as opposed to manifold pressure.=A0 =A0If you have an EM2 engine = monitor to display the data, you can use a copy of this chart to record your table = data after the engine is tuned

 

 

Not that there are two conditions that must be met = before the EC3/EC2 uses only rpm to determine the lower operating point.=A0 The = engine rpm must be below 2300 AND the manifold pressure must be below 13” = Hg.=A0 So that implies that if you are operating at 2000 rpm, but your manifold pressure is at 13.5 or 14 or higher then the EC2 is using the manifold = pressure to determine the operating point and not the = rpm.

 

So lets say you are trying to start your engine = – rpm < 2300 but manifold pressure > 13.=A0 Therefore the MCT pointer may be = pointing to the bin corresponding to a manifold pressure that is close to ambient = (29.92” Hg).=A0 That is also the point for WOT throttle (Lots of fuel).=A0 So = its safe to say that on the first turn of the prop that is where your Ec3/2 is = at.=A0 The instance the engine fires, the manifold pressure immediately begins to = drop – how fast it drops will depend in part on what throttle setting you = have.=A0 If you throttle is closed, the manifold pressure will almost immediately = drop to low values (presumably below 13” hg) and all is well.=A0 If = however, your throttle is set at =BC or more open, then the manifold pressure is not = as likely to drop below 13” hg.=A0 If this is the case, then the operating = point is going to be based on manifold pressure which may be considerably above = 13” Hg.=A0 That point in turn may be overly rich for idle conditions and = your engine fails to sustain operation do to excess fuel and = floods.

 

Tracy, of course, may have algorithms to deal with this, but based solely on the comments = in the manual – looks like this could happen.=A0 Particularly in the = early stages, before you get the MCT tuned.

 

Thought I would pass=A0 this on – my older EC2 = only uses manifold pressure across the entire range.

 

Ed

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.r= otaryaviation.com/Rotorhead%20Truth.htm

 

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