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 1916570 for flyrotary@lancaironline.net; Mon, 12 Mar 2007 10:34:08 -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 <20070312143315.KNCE2807.fed1rmmtao106.cox.net@fed1rmimpo01.cox.net> for ; Mon, 12 Mar 2007 10:33:15 -0400 Received: from BigAl ([72.192.132.90]) by fed1rmimpo01.cox.net with bizsmtp id ZqZF1W0061xAn3c0000000; Mon, 12 Mar 2007 10:33:15 -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 07:33:28 -0800 Message-ID: <000001c764bb$c8a4bd50$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C76478.BA817D50" 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_0001_01C76478.BA817D50 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable 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_0001_01C76478.BA817D50 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

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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