X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 17 Apr 2010 22:21:39 -0400 Message-ID: X-Original-Return-Path: Received: from smtp0.av-mx.com ([137.118.16.56] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with ESMTP id 4224709 for lml@lancaironline.net; Sat, 17 Apr 2010 11:05:37 -0400 Received-SPF: pass receiver=logan.com; client-ip=137.118.16.56; envelope-from=pinetownd@volcano.net Received: from DennisPC (65-174-0-178.dsl.volcano.net [65.174.0.178]) (Authenticated sender: pinetownd@volcano.net) by smtp0.av-mx.com (Postfix) with ESMTP id 48C8E1BFD35 for ; Sat, 17 Apr 2010 11:04:59 -0400 (EDT) X-Original-Message-ID: <01E4477C1E494F598301E5602600675F@DennisPC> From: "Dennis Johnson" X-Original-To: "Lancair Mailing List" References: In-Reply-To: Subject: Re: [LML] Re: Fuel Pressure Setup X-Original-Date: Sat, 17 Apr 2010 08:05:00 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0140_01CADE04.AD994920" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18005 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18005 This is a multi-part message in MIME format. ------=_NextPart_000_0140_01CADE04.AD994920 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Bruce, I have a true fuel flow sensor (not a fuel pressure-type sensor) between = the engine driven fuel pump and the throttle body. The Lancair IO-550 N = or G engines I've seen have the fuel flow sensor there (but I haven't = seen that many, so I might have seen an unrepresentative sample). All = the fuel that leaves the engine driven fuel pump has no place else to go = except through the throttle and then through the spider and then through = the injectors and then into the cylinders, since there is no fuel return = line downstream from the pump. Putting the fuel flow sensor between the = pump and the throttle body or between the throttle body and the spider = would give the identical reading. There is more room to install it = between the pump and the throttle. Maybe you're thinking of a different = engine with a different configuration? Regarding fuel pressure, I'm measuring fuel pressure at the injectors, = which seems to me to be the more relevant metric. This seems to be = supported by TCM's SID 97-3 fuel system setup instructions, which says = that full power unmetered fuel pressure is shown for reference only and = that full power adjustments should be done based on metered fuel = pressure. =20 As a practical matter, except for adjusting the fuel system according to = SID 97, I don't think it makes a whole lot of difference if you're = measuring metered or unmetered fuel pressure. If whatever you're = measuring suddenly changes, it's worth taking a look to find out what's = going on. I'm not an expert on this and hope someone will correct me if I'm wrong. Best, Dennis ------=_NextPart_000_0140_01CADE04.AD994920 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Hi Bruce,

I have a true fuel flow sensor (not a fuel pressure-type sensor) = between=20 the engine driven fuel pump and the throttle body. The Lancair = IO-550 N or=20 G engines I've seen have the fuel flow sensor there (but I haven't seen = that=20 many, so I might have seen an unrepresentative sample). All the = fuel that=20 leaves the engine driven fuel pump has no place else to go except = through the=20 throttle and then through the spider and then through the injectors and = then=20 into the cylinders, since there is no fuel return line downstream from = the=20 pump. Putting the fuel flow sensor between the pump and the = throttle body=20 or between the throttle body and the spider would give = the identical=20 reading. There is more room to install it between the pump and the = throttle. Maybe you're thinking of a different engine with a = different=20 configuration?

Regarding fuel pressure, I'm measuring fuel pressure at the = injectors,=20 which seems to me to be the more relevant metric. This seems = to be=20 supported by TCM's SID 97-3 fuel system setup instructions, which = says that=20 full power unmetered fuel pressure is shown for reference only and=20 that full power adjustments should be done based on metered fuel=20 pressure.

As a practical matter, except for adjusting the fuel system = according to=20 SID 97, I don't think it makes a whole lot of difference if you're = measuring=20 metered or unmetered fuel pressure. If whatever you're measuring = suddenly=20 changes, it's worth taking a look to find out what's going on.

I'm not an expert on this and hope someone will correct me if I'm=20 wrong.

Best,

Dennis

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