Return-Path: <13brv3@bellsouth.net> Received: from imf18aec.mail.bellsouth.net ([205.152.59.66] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 485743 for flyrotary@lancaironline.net; Mon, 25 Oct 2004 12:31:55 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.66; envelope-from=13brv3@bellsouth.net Received: from rd ([65.6.194.9]) by imf18aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20041025163124.EJXE2398.imf18aec.mail.bellsouth.net@rd> for ; Mon, 25 Oct 2004 12:31:24 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] TWM MAP measurement Date: Mon, 25 Oct 2004 11:31:47 -0500 Message-ID: <01de01c4bab0$1f3b31c0$6101a8c0@rd> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_01DF_01C4BA86.366529C0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_01DF_01C4BA86.366529C0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Maybe you're comparing apples and cherimoyas. =20 After a brief Google search, I now know what a cherimoya is. Measuring MAP at the downstream end of the TB "runners" is different = than measuring out in the air plenum before any losses. It is difficult to believe there is 4" drop, but until we have some other measurements, we don't know for sure. On my dyno runs I also measured 26" at 6200 WOT. As I understand it, the ideal situation would be to have a TB, that = feeds into an air plenum, then individual runners from there to the engine. = It sounds like the only place you can get a true, overall MAP reading is in = the air plenum itself. I'm guessing that it's difficult to get a good = reading in the TB bore, due to the speed the air is moving. Trying to sense the = MAP after a restriction (downwind end of the runners) will be a different, = but still interesting MAP reading. =20 =20 It seems to me that the gold standard of MAP readings almost requires a reading to be taken in the plenum, and only then will it conform to the expected 30" at WOT. My theory is that our TWM readings are perfectly usable for tuning, and as a reference number, but will never see 30" at = WOT due to the construction of the port, and velocity of the air inside the = TB. I could certainly be wrong, and I'd love to pick up an extra 4" MAP, but = I can't see that happening. =20 What is the orientation of your TB - MAP line coming off the top of the = TB or off the bottom?=20 Port off the top. =20 Cheers, Rusty ------=_NextPart_000_01DF_01C4BA86.366529C0 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message

Maybe you’re comparing apples and = cherimoyas. 

After a brief Google search, I now = know what a=20 cherimoya is.

Measuring MAP at the downstream end of the TB = “runners” is=20 different than measuring out in the air plenum before any losses.  = It is=20 difficult to believe there is 4” drop, but until we have some = other=20 measurements, we don’t know for sure.  On my dyno runs I also = measured 26”=20 at 6200 WOT.

As I = understand it, the=20 ideal situation would be to have a TB, that feeds into an air plenum, = then=20 individual runners from there to the engine.  It sounds like the = only place=20 you can get a true, overall MAP reading is in the air plenum = itself.  I'm=20 guessing that it's difficult to get a good reading in the TB bore, due = to the=20 speed the air is moving.  Trying to sense the MAP after a = restriction=20 (downwind end of the runners) will be a different, but still interesting = MAP=20 reading. 
 
It seems = to me that the=20 gold standard of MAP readings almost requires a reading to be taken in = the=20 plenum, and only then will it conform to the expected 30" at WOT.  = My=20 theory is that our TWM readings are perfectly usable for tuning, and as = a=20 reference number, but will never see 30" at WOT due to the construction = of the=20 port, and velocity of the air inside the TB.   I could = certainly be=20 wrong, and I'd love to pick up an extra 4" MAP, but I can't see that=20 happening. 

What is the orientation of your TB – MAP line coming off the = top of the TB or=20 off the bottom?

Port off the top.  =

Cheers,
Rusty
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