X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3690484 for flyrotary@lancaironline.net; Sun, 21 Jun 2009 23:55:10 -0400 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (sv1-1.per.aanet.com.au [203.24.100.68]) by poplet2.per.eftel.com (Postfix) with ESMTP id 333AD1739D0 for ; Mon, 22 Jun 2009 11:54:26 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id CA7B41153964 for ; Mon, 22 Jun 2009 11:54:24 +0800 (WST) Message-ID: From: "George Lendich" To: "Rotary motors in aircraft" Subject: Duty Cycle for Injectors Date: Mon, 22 Jun 2009 13:54:25 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0005_01C9F340.F4053BD0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5512 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Antivirus: avast! (VPS 090621-0, 06/21/2009), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0005_01C9F340.F4053BD0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, I remember reading that the 80% duty cycle rule (of thumb)was originally = developed for the racing industry. Given that probably 100% will never be reached in the day to day vehicle = use - the 80 % duty cycle most probably doesn't apply for sizing. = However bigger injectors are standard in vehicles where the RPM limit is = much higher than what we may experience in our Aviation application, = even if for only short periods of time. Given that our RPM is on the high end for climb and take-off, but not as = high as it could be (not max RPM), and cruise is for the most part only = 6,000 rpm, do we really have to held to the 80% DC rule, where perhaps = 90% DC (for short periods of time) may well give sufficient safety = margin to maintain longevity of the injectors. Not that there is a major benefit in having borderline injector duty = cycle, as you so rightly pointed out - it's just that it would be = interesting to know! George (down under) ------=_NextPart_000_0005_01C9F340.F4053BD0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Ed,

I remember reading that the 80% duty = cycle rule (of=20 thumb)was originally developed for the racing industry.

Given that probably 100% will never be = reached in=20 the day to day vehicle use - the 80 % duty cycle most probably = doesn't=20 apply for sizing. However bigger injectors are standard in vehicles = where the=20 RPM limit is much higher than what we may experience in our Aviation=20 application, even if for only short periods of time.

Given that our RPM is on the high end = for climb and=20 take-off, but not as high as it could be (not max RPM), and cruise is = for the=20 most part only 6,000 rpm, do we really have to held to the 80% DC rule, = where=20 perhaps 90% DC (for short periods of time) may well give sufficient = safety=20 margin to maintain longevity of the injectors.

Not that there is a major benefit in = having=20 borderline injector duty cycle, as you so rightly pointed out - = it's just=20 that it would be interesting to=20 know!

George (down = under)

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