Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Wed, 29 Dec 2004 00:10:34 -0500 Message-ID: X-Original-Return-Path: Received: from imo-m26.mx.aol.com ([64.12.137.7] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 582966 for lml@lancaironline.net; Tue, 28 Dec 2004 22:56:21 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.7; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-m26.mx.aol.com (mail_out_v37_r3.8.) id q.8d.1d30a1cd (4410) for ; Tue, 28 Dec 2004 22:55:45 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <8d.1d30a1cd.2f0384c1@aol.com> X-Original-Date: Tue, 28 Dec 2004 22:55:45 EST Subject: Re: [LML] Re: airspeed vs. power X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1104292545" X-Mailer: 9.0 Security Edition for Windows sub 5000 -------------------------------1104292545 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 12/28/2004 9:08:44 P.M. Central Standard Time, Walter@advancedpilot.com writes: One of the problems with some fuel pressure systems is that they maintain a fixed pressure with little change while the FF actually changes significantly. If the system is a fuel pressure system of gauge display, you will not see the FF change that is actually happening. If you have a FF transducer in one of those systems, you can see this by the differences between the two instruments. Walter, where is this going? I said I have a fuel flow sensor (located between throttle body and spider) and it did change when the MAP was reduced 1". This is one thing I do not like about the TCM FADEC. It displays a fuel pressure which does not change significantly with rather large changes in FF. In many carbureted installations, the fuel flow instrument is actually fuel pressure and does not show the FF changes accurately. I am not sure how the Mooney system is set up. I do have a great deal of confidence in telling you that as you reduce throttle from WOT, the first 3/4 to 1 inch of throttle travel does not reduce MP -- it reduces FF only. This is the very important fuel enrichment feature that is built into almost all carburetors. A very, very few do not have this, and they are almost always found on turbo-supercharged engines like the big radials. I was talking about injected systems. I have no idea how a Mooney is set up. I do not have a carburetor. Anyway, we are so far from my observations that I have no idea what your point is. In a fuel injected system, the reduction of WOT by 1" MAP is a power reduction of similar magnitude as the dropping of the WOT 2500 RPM by 100 - The drop in airspeed should be similar and so should the drop in fuel flow - similar, not identical. In our slick Lancairs with little parasitic drag, the drop is merely a few knots. If the "indicated" 1" MAP drop resulted in a large drop in airspeed and fuel flow, there is something wrong with the MAP sensor circuit, such as a problem with the snubber valve (if VM engine instrumentation is used). The procedure is an in-flight diagnostic tool. Do I need more qualifications or specificity? Scott Krueger AKA Grayhawk Lancair N92EX IO320 Aurora, IL (KARR) -------------------------------1104292545 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 12/28/2004 9:08:44 P.M. Central Standard Time,=20 Walter@advancedpilot.com writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>One of=20 the problems with some fuel pressure systems is that they
maintain a f= ixed=20 pressure with little change while the FF actually
changes=20 significantly. If the system is a fuel pressure system of
gauge=20 display, you will not see the FF change that is actually
happening.&nb= sp;=20 If you have a FF transducer in one of those systems, you
can see this=20= by=20 the differences between the two instruments.

Walter, where is this going? I said I have a fuel flow sensor=20 (located between throttle body and spider) and it did change when the MAP wa= s=20 reduced 1".

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
This=20 is one thing I do not like about the TCM FADEC. It displays a
fu= el=20 pressure which does not change significantly with rather large
changes= in=20 FF.

In many carbureted installations, the fuel flow instrument is=20 actually
fuel pressure and does not show the FF changes accurately.&nb= sp;=20 I am not
sure how the Mooney system is set up. I do have a great= =20 deal of
confidence in telling you that as you reduce throttle from WOT= ,=20 the
first 3/4 to 1 inch of throttle travel does not reduce MP -- it=20 reduces
FF only. This is the very important fuel enrichment feat= ure=20 that is
built into almost all carburetors. A very, very few do n= ot=20 have this,
and they are almost always found on turbo-supercharged engi= nes=20 like the
big radials.

I was talking about injected systems. I have no idea how a Mooney= is=20 set up. I do not have a carburetor.

Anyway, we are so far from my observations that I have no idea what you= r=20 point is.

In a fuel injected system, the reduction of WOT by 1" MAP is a power=20 reduction of similar magnitude as the dropping of the WOT 250= 0=20 RPM by 100 - The drop in airspeed should be similar and so should the drop i= n=20 fuel flow - similar, not identical. In our slick Lancairs with little=20 parasitic drag, the drop is merely a few knots. If the "indicated" 1"=20= MAP=20 drop resulted in a large drop in airspeed and fuel flow, there is somet= hing=20 wrong with the MAP sensor circuit, such as a problem with the snub= ber=20 valve (if VM engine instrumentation is used). The=20 procedure is an in-flight diagnostic tool. Do I need more=20 qualifications or specificity?=20

Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 Aurora, IL=20 (KARR)

-------------------------------1104292545--