X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 64 [XX] (50%) BODY: contains text similar to "low payment" (25%) SPAMTRICK: obfuscated phone number (-25%) BODY: correction: likely legitimate obfuscated series of numbers Return-Path: Received: from cottonwood.uwyo.edu ([129.72.10.27] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with ESMTP id 1915174 for flyrotary@lancaironline.net; Sun, 11 Mar 2007 14:25:19 -0400 Received-SPF: none receiver=logan.com; client-ip=129.72.10.27; envelope-from=sboese@uwyo.edu Received: from UWMAIL.uwyo.edu (uwmail.uwyo.edu [172.26.4.76]) by cottonwood.uwyo.edu (8.12.11.20060614/8.12.11) with ESMTP id l2BIOF4h025223 for ; Sun, 11 Mar 2007 12:24:20 -0600 (MDT) (envelope-from sboese@uwyo.edu) Received: from SBPortable ([10.88.84.92]) by UWMAIL.uwyo.edu with Microsoft SMTPSVC(6.0.3790.1830); Sun, 11 Mar 2007 12:24:11 -0600 From: "Steven Boese" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] A solution? was : The truth??? / Injector flow rate mystery solved Date: Sun, 11 Mar 2007 12:21:53 -0600 Message-ID: <001f01c7640a$25912bf0$5c54580a@gg.uwyo.edu> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0020_01C763D7.DAF6BBF0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.2627 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-OriginalArrivalTime: 11 Mar 2007 18:24:12.0461 (UTC) FILETIME=[77BC05D0:01C7640A] This is a multi-part message in MIME format. ------=_NextPart_000_0020_01C763D7.DAF6BBF0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Ed and Joe, The diode in the EC2 allows the current from the collapse of the injector magnetic field to flow to the positive supply rail (~14V); it doesn't oppose this. A resistor allowing this current to flow would also result in a close delay since the current flowing is what maintains the magnetic field during this delay. What is needed is a way to decrease the rate of voltage rise just after the EC2 pulse ends so arcing in the A/B selection relay is suppressed. After the relay contacts open enough that an arc is no longer possible (which shouldn't take long) an open circuit condition now would allow the injector to close quickly. The arcing may or may not be a problem any given time the relay is opened since the timing of the end of the EC2 pulse and the opening of the relay are independent and arbitrary. One possible solution is a RC snubber rather than the resistor that Joe proposed. I think Tracy is working on checking this out. I have installed this in my plane and it works. Tracy, however can do a much more thorough job of evaluating this and be sure the change is reliable. Let's give him a chance to do this before we do something we wish we hadn't. Steve -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson Sent: Sunday, March 11, 2007 9:16 AM To: Rotary motors in aircraft Subject: [FlyRotary] A solution? was : The truth??? / Injector flow rate mystery solved Sounds like a reasonable approach to me Joe. A pull-down resistor would be relatively easy for me to install - I have the resistor pack required for the peak-hold type injectors. So I could easily place four additional resistors in that box. If I understand you (please correct me if I don't), the pull down resistor should go between the injector and the EC2 sinking terminals. That way the current induced when the intended pulse terminates and the magnetic field collapses will have a path to ground rather than being opposed by the diode in the Ec2. The value of said resistor could be around 100 ohms. Since the induced voltage could reach from 50 - 100+ volts an 100 ohm resistor could flow from 0.5 - 1 Amp (for a very short duration). As far as affecting the 12 Volt signal it would only draw 12/100 = 0.12 amp or 120 milliamps. That would be pulled through the injectors at all times. The injector resistance is probably (peak and hold case) around 3 ohms. So the injector would draw 12/3 = 4 amps (DC case - its undoubtedly less due to the A/C impedance of the coil). It make take some experimenting - but 100 ohm looks like a good place to start. The wattage should probably be around 5 - 10 watts just to be on the safe side. So certainly looks like a suggestion that would work, Joe. Ed ------=_NextPart_000_0020_01C763D7.DAF6BBF0 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message

Ed and = Joe,

 

The diode in the EC2 allows the = current from the collapse of the injector magnetic field to flow to the positive = supply rail (~14V); it doesn’t oppose this.  A resistor allowing this current to flow would also result in a = close delay since the current flowing is what maintains the magnetic field = during this delay.   What is = needed is a way to decrease the rate of voltage rise just after the EC2 pulse ends = so arcing in the A/B selection relay is suppressed.  After the relay contacts open = enough that an arc is no longer possible (which shouldn’t take long) an = open circuit condition now would allow the injector to close quickly.  The arcing may or may not be a = problem any given time the relay is opened since the timing of the end of the = EC2 pulse and the opening of the relay are independent and arbitrary.   One possible solution is = a RC snubber rather than the resistor that Joe = proposed.  I think = Tracy is working on checking this out.  I have installed this in my = plane and it works.  = Tracy, however can do a much more thorough job of evaluating this = and be sure the change is reliable.  = Let’s give him a chance to do this before we do something we wish we = hadn’t.

 

Steve

  

 

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: = Sunday, March 11, = 2007 9:16 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] A = solution? was : The truth??? / Injector flow rate mystery solved

 

Sounds like a reasonable approach  to me Joe.   A pull-down = resistor would be relatively easy  for me to install  - I have the resistor pack required for the peak-hold type injectors.  So I = could easily place four additional resistors in that = box.

 

If I understand you (please = correct me if I don't), the pull down resistor should go between the injector = and the EC2 sinking terminals.  That way the current induced when the = intended pulse terminates and the magnetic field collapses will have a path to = ground rather than being opposed by the diode in the = Ec2.

 

The value of said resistor = could be around 100 ohms.  Since the induced voltage could reach from 50 - = 100+ volts an 100 ohm resistor could flow from

0.5 - 1 Amp (for a very = short duration).  As far as affecting the 12 Volt signal it would only = draw 12/100 =3D 0.12 amp or 120 milliamps.  That would be pulled through = the injectors at all times.  The injector resistance is = probably (peak and hold case) around 3 ohms.  So the injector would draw 12/3 =3D = 4 amps (DC case - its undoubtedly less due to the A/C impedance of the = coil).  It make take some experimenting - but 100 ohm looks like a good place to = start.

 

The wattage should probably = be around 5 - 10 watts just to be on the safe side.  =

 

So certainly looks like a = suggestion that would work, Joe. 

 

 

Ed

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