Return-Path: Received: from [65.54.169.74] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.2b5) with ESMTP id 143536 for flyrotary@lancaironline.net; Mon, 07 Jun 2004 20:38:41 -0400 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Mon, 7 Jun 2004 17:38:10 -0700 Received: from 4.174.4.139 by bay3-dav44.bay3.hotmail.com with DAV; Tue, 08 Jun 2004 00:38:10 +0000 X-Originating-IP: [4.174.4.139] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: LS1 Coils - amp draw? Date: Mon, 7 Jun 2004 20:38:08 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00F2_01C44CCF.5775DDA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MIMEOLE: Produced By MSN MimeOLE V9.00.0013.2101 Seal-Send-Time: Mon, 7 Jun 2004 20:38:08 -0400 Message-ID: X-OriginalArrivalTime: 08 Jun 2004 00:38:10.0629 (UTC) FILETIME=[DFF27F50:01C44CF0] This is a multi-part message in MIME format. ------=_NextPart_000_00F2_01C44CCF.5775DDA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Sunday, June 06, 2004 2:35 PM Subject: [FlyRotary] Re: LS1 Coils - amp draw? The peak current draw on the LS1 coils is 9A EACH. This can happen = on startup before the EC2 can compute the proper dwell time. Average = amps is much lower during normal operation. Prior to any discussion of fuses vs CBs; this issue needs some = clarification. Is it possible for more than one coil to be drawing this = level of current at the same time? I have 6 coils on my 20B; three on = each circuit with a 16 AWG wire. This could be frightening!=20 Al=20 Don't think it is a worry. All can be on for a short time = (possibly long enough to blow a fast acting fuse) but not long enough to = heat a 16 ga wire significantly.=20 Tracy Tracy; Well; the worry is this. Safe wiring practice requires being able = to protect the wire, especially if it is in a bundle or close proximity = with other wires, against any failure which would overload the wire. = Running the numbers says that the maximum safe current for a 16 awg wire = is 15 amps. If I interpret you correctly; it is possible for my coil = power lead to have to carry 27 amps (for 3 coils) for a short time, = which would trip a breaker, or blow a fuse. Under these conditions one = can not properly protect the wire against a potential short - unless a = much larger wire is used. My wires run in a wiring duct, which isn't = exactly a bundle, but the analysis says for 27 amps in a bundle you need = about a #10 wire. Further; I went to great lengths to maintain the redundancy that you = also strived for in the ECU with the dual controllers and the isolation = switches. I have the engine critical bus connected to the dual battery = system, and isolated by 40 amp diodes. I think you're suggesting that = it's possible for the coils to momentarily draw 54 amps (6 x 9), plus = pump and injectors; maybe up to nearly 70 amps. Ain't gonna work. So what am I misunderstanding here, or how do we get around this? = Under what temporary condition can this high current exist? Is there an = operational sequence to avoid this possible condition? Thanks, Al Oh darn, I knew this would happen.=20 The momentary 9A load on each coil only lasts in the range of 50 - = 100 milliseconds under worst case conditions during start sequence. = There is no way to avoid it but FWIW, it just isn't a problem. The = 16ga wire would not have time to get even warm. The specs you are = discussing relate only to long term events and do not address short term = transients. =20 Tracy ------=_NextPart_000_00F2_01C44CCF.5775DDA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
 

-----=20 Original Message -----

From: Al=20 Gietzen

To: Rotary motors in = aircraft=20

Sent:=20 Sunday, = June 06,=20 2004=20 2:35=20 PM

Subject: = [FlyRotary] Re:=20 LS1 Coils - amp draw?

 

 

The=20 peak current draw on the LS1 coils is 9A EACH.   This can = happen=20 on startup before the EC2 can compute the proper dwell time.  = Average=20 amps is much lower during normal operation.

 

 

Prior = to any=20 discussion of fuses vs CBs; this issue needs some clarification. =  Is it=20 possible for more than one coil to be drawing this level of current = at the=20 same time?  I have 6 coils on my 20B; three on each circuit = with a 16=20 AWG wire.  This could be frightening!

 

Al=20

 

Don't = think it=20 is a worry.   All can be on for a short time (possibly = long enough=20 to blow a fast acting fuse) but not long enough to heat a 16 ga wire = significantly. 

Tracy

 

Tracy;

 

Well; = the worry=20 is this.  Safe wiring practice requires being able to protect = the wire,=20 especially if it is in a bundle or close proximity with other wires, = against=20 any failure which would overload the wire.  Running the numbers = says=20 that the maximum safe current for a 16 awg wire is 15 amps.  If = I=20 interpret you correctly; it is possible for my coil power lead to = have to=20 carry 27 amps (for 3 coils) for a short time, which would trip a = breaker, or=20 blow a fuse.  Under these conditions one can not properly = protect the=20 wire against a potential short =96 unless a much larger wire is = used.  My=20 wires run in a wiring duct, which isn=92t exactly a bundle, but the = analysis=20 says for 27 amps in a bundle you need about a #10 = wire.

 

Further; I went=20 to great lengths to maintain the redundancy that you also strived = for in the=20 ECU with the dual controllers and the isolation switches.  I = have the=20 engine critical bus connected to the dual battery system, and = isolated by 40=20 amp diodes.  I think you=92re suggesting that it=92s possible = for the coils=20 to momentarily draw 54 amps (6 x 9), plus pump and injectors; maybe = up to=20 nearly 70 amps.  = Ain=92t=20 gonna work.

 

So what = am I=20 misunderstanding here, or how do we get around this?  Under = what=20 temporary condition can this high current exist?  Is there an=20 operational sequence to avoid this possible = condition?

 

Thanks,

 

Al

 

Oh darn,=20 I knew this would happen. 

 

 The=20 momentary 9A load on each coil only lasts in the range of 50 - = 100=20 milliseconds under worst case conditions during start = sequence.  There=20 is no way to avoid it but FWIW, it just isn't a problem.   = The=20 16ga wire would not have time to get even warm.   The = specs you=20 are discussing relate only to long term events and do not = address short=20 term transients.  

 

Tracy

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