X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 30 [X] Return-Path: Received: from fed1rmmtao106.cox.net ([68.230.241.40] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with ESMTP id 1916660 for flyrotary@lancaironline.net; Mon, 12 Mar 2007 11:15:22 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.40; envelope-from=alventures@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao106.cox.net (InterMail vM.7.05.02.00 201-2174-114-20060621) with ESMTP id <20070312151426.LEYB2807.fed1rmmtao106.cox.net@fed1rmimpo01.cox.net> for ; Mon, 12 Mar 2007 11:14:26 -0400 Received: from BigAl ([72.192.132.90]) by fed1rmimpo01.cox.net with bizsmtp id ZrER1W00N1xAn3c0000000; Mon, 12 Mar 2007 11:14:25 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: A solution? Injector flow rate mystery solved Date: Mon, 12 Mar 2007 08:14:40 -0800 Message-ID: <000101c764c1$897488d0$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0002_01C7647E.7B5148D0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0002_01C7647E.7B5148D0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hum-m-m - just registered with me that the comments I pasted along = earlier are based on the assumption of driving 'Peak and Hold' injectors rather = than the 'Saturation' type. May change the conclusions. =20 Al G =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen Sent: Monday, March 12, 2007 7:33 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: A solution? Injector flow rate mystery solved =20 Subject: [FlyRotary] Re: A solution? was : The truth??? / Injector flow = rate mystery solved =20 What about MOV's? Typical transient response time measured in nanoseconds... =20 My expert, who has designed ECUs for other applications, had the = following comments that may be of interest: =20 As far as the ECU goes, the diodes should be replaced with=20 tranzorbs or zeners of about 30 volts. I don't think a pull down = resistor=20 of 1K as suggested will do anything at all. It should be roughly 8 = times=20 the injector resistance (assuming the injector hold current is less than = 8=20 times the pull-in current -- typically it's between 4 and 6). And if = you=20 want a true peak and hold injector driver, then the National LM1949 is = the=20 way to go. =20 The resistor only makes=20 sense at very high RPMs, probably higher than what the engine can do, so = I=20 consider it optional. The relay contacts are not the issue. The issue = is=20 protecting the drive transistor which will fail at voltages lower than = what=20 will cause an arc in the relay (not to mention RF noise). The other = issue=20 is minimizing the current flow as the magnetic field collapses. =20 As previously mentioned, the 'correct' way to drive a high flow rate injector is using a=20 peak and hold circuit. =20 FWIW; =20 Al G =20 ------=_NextPart_000_0002_01C7647E.7B5148D0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hum-m-m – just registered = with me that the comments I pasted along earlier are based on the assumption of = driving ‘Peak and Hold’ injectors rather than the = ‘Saturation’ type. May change the conclusions.

 

Al G

 

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Monday, March 12, = 2007 7:33 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = A solution? Injector flow rate mystery solved

 

Subject: [FlyRotary] Re: A solution? was : The truth??? / Injector flow rate = mystery solved

 

What about MOV's?  = Typical transient response time measured in nanoseconds...

   <Marv>  

My expert, who has designed ECUs for other applications, had the following comments that may be of interest:

 

As = far as the ECU goes, the diodes should be replaced with

tranzorbs or zeners of about 30 volts.  I don't think a pull down resistor =

of = 1K as suggested will do anything at all.  It should be roughly 8 times =

the = injector resistance (assuming the injector hold current is less than 8 =

times the pull-in current -- typically it's between 4 and 6).  And if you =

want = a true peak and hold injector driver, then the National LM1949 is the =

way to = go.

 

The = resistor only makes

sense at very high RPMs, probably higher than what the engine can do, so I =

consider it optional.  The relay contacts are not the issue.  The issue is =

protecting the drive transistor which will fail at voltages lower than what =

will = cause an arc in the relay (not to mention RF noise).  The other issue =

is = minimizing the current flow as the magnetic field collapses.

 

As = previously mentioned, the ‘correct’ way to drive a high flow rate = injector is using a

peak and hold = circuit.

 

FWIW;

 

Al = G

 
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