X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 949678 for flyrotary@lancaironline.net; Thu, 19 May 2005 08:32:25 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-065-188-083-049.carolina.res.rr.com [65.188.83.49]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j4JCVZL5029804 for ; Thu, 19 May 2005 08:31:37 -0400 (EDT) Message-ID: <000d01c55c6e$b6474850$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: More MAP measurement questions Date: Thu, 19 May 2005 08:31:42 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000A_01C55C4D.2EFC6FE0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_000A_01C55C4D.2EFC6FE0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageHi George, I'll give it a shot. The Ec2 basically determines how much fuel to = inject using two factors - MAP (Manifold Absolute Pressure) and OAT = which basically tells it how dense the air is that the engine is = ingesting from the manifold. The Ec2 then examines its memory settings = (a different Map - read further)programmed in its memory (which you can = adjust with a mixture knob) for that manifold pressure match. Since the = manifold pressure can vary from apporx 12" Hg to 30"Hg (non-turbo), = there are a series of memory locations generally also referred to as the = MAP (MAP in this case referring to a topological chart) of the fuel = settings. If you plot the fuel mixture settings against RPM and Pressure = it looks like a 2 dim map). So once it matches the manifold pressure = it senses through the manifold pressure sensors with the corresponding = memory location it extracts the injector timing for that MAP and sends = it on to the injectors (with corrections for air temp). The injectors fire once per revolution of the E shaft (which corresponds = to one face of an rotor, therefore, the faster the rpm the more = frequently the injectors fire. But, it basically provides the same = amount of fuel per revolution per specific manifold pressure (which of = course is controlled by the throttle setting and engine rpm) perhaps = adjusted for Ve and OAT. Manifold Absolute Pressure is also one parameter to determine how well = you induction system is working. At sea level the MAP is 29.92" Hg. So = when you open your throttle wide open, you would like to see 29.92" Hg = on the gauge. If you do not and see less than 29.92"Hg (at sea level) = then that implies there is a restriction in your intake and a resulting = pressure loss. Less pressure means less dense air in the manifold which = means less fuel can be burnt which means less power. =20 That is the reason Rusty is concerned about whether the MAP he is seeing = really reflects what his engine is seeing or some fluke of where the = sensing port is in the intake. Generally you would like to have less = that 1/2" of a pressure drop any more than that (if its real) and you = are starting to loose power potential. So if the drop is real then = Rusty probably wants to modify his intake to eliminate it - if its just = a fluke of where he is sensing it - then he does not need to go to the = trouble of designing and fabricating a new intake. =20 That's my take on it. Hope it helps. Ed ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Thursday, May 19, 2005 2:13 AM Subject: [FlyRotary] Re: More MAP measurement questions Al,Rusty and All, Excuse my ignorance here, I have absolutely no knowledge about how = ECU's work. I've heard people say that it reads MAP settings - so what = is a MAP, and if it's different because the pressure is different at = different places in the inlet, how can the computer calculate the inlet = charge and timing. I'm confused! George ( down under) Greetings, I'm working on a new theory about my low MAP reading. The theory is = that this isn't a problem at all, but rather a difference in the way = it's being measured. =20 What's new about this theory? This is what I was telling you a week = or two ago. J I apologize for lack of clarity, causing you to have to re-invent = this theory. Al (Also running TWM TB) The TWM TB has a MAP port about 4 inches past the entrance of the TB = throat. That means I'm measuring the air pressure on the suction side = of the largest restriction in the system (from wide open space, to 41mm = tube). Since there's no significant restriction downstream from the = TB, I would guess that I could measure the MAP at the inlet of the side = housing, and wouldn't find it significantly lower than what I'm seeing = in the TWM TB. In other words, I'm measuring the worst possible MAP, = which is the suction side. =20 From what I understand, the typical (if there is such a thing) = intake has a large TB, feeding into an open plenum, then into the = smaller runners that go to the engine. If I'm not mistaken, virtually = everyone is measuring their MAP in the open plenum, before the air has = to enter the smaller runners to go to the engine. In other words, the = people who are reading 30" are doing it on the pressure side of the = largest restriction. =20 I could babble on about this, but my point is to ask where others = are measuring their MAP (turbo folks need not apply). You'll also have = to give a general description of your intake layout. I already know = that Ed and Tracy are using the "typical" situation. Is anyone = measuring MAP in the runner to the engine? =20 Cheers, Rusty (duty calls...) =20 ------=_NextPart_000_000A_01C55C4D.2EFC6FE0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Hi George,
 
I'll give it a shot.  The Ec2 basically = determines=20 how much fuel to inject using two factors - MAP (Manifold Absolute = Pressure) and=20 OAT which basically tells it how dense the air is that the engine is = ingesting=20 from the manifold.  The Ec2 then examines its = memory settings (a=20 different Map - read further)programmed  in its memory (which you = can=20 adjust with a mixture knob) for that manifold pressure match.  = Since the=20 manifold pressure can vary from apporx 12" Hg to 30"Hg (non-turbo), = there are a=20 series of memory locations generally also referred to as the MAP (MAP in = this=20 case referring to a topological chart) of the fuel settings. If you plot = the=20 fuel mixture settings against RPM and Pressure it looks like a 2 = dim=20 map).    So once it matches the manifold pressure it senses = through=20 the manifold pressure sensors with the corresponding memory location it = extracts=20 the injector timing for that MAP and sends it on to the injectors (with=20 corrections for air temp).
 
The injectors fire once per revolution of the E = shaft=20 (which corresponds to one face of an rotor, therefore, the faster the = rpm the=20 more frequently the injectors fire.  But, it basically provides the = same=20 amount of fuel per revolution per specific manifold pressure (which of = course is=20 controlled by the throttle setting and engine rpm) perhaps adjusted for = Ve and=20 OAT.
 
Manifold Absolute Pressure is also one parameter = to=20 determine how well you induction system is working.  At sea level = the MAP=20 is 29.92" Hg.  So when you open your throttle wide open, you would = like to=20 see 29.92" Hg on the gauge.  If you do not and see less than = 29.92"Hg (at=20 sea level) then that implies there is a restriction in your intake and a = resulting pressure loss.  Less pressure means less dense air in the = manifold which means less fuel can be burnt which means less = power.  =20
 
That is the reason Rusty is concerned about = whether the=20 MAP he is seeing really reflects what his engine is seeing or some fluke = of=20 where the sensing port is in the intake.  Generally you would like = to have=20 less that 1/2" of a pressure drop any more than that (if its real) and = you are=20 starting to loose power potential.  So if the drop is real then = Rusty=20 probably wants to modify his intake to eliminate it - if its just a = fluke of=20 where he is sensing it - then he does not need to go to the trouble of = designing=20 and fabricating a new intake. 
 
That's my take on it.  Hope it = helps.
 
Ed
----- Original Message -----
From:=20 George=20 Lendich
Sent: Thursday, May 19, 2005 = 2:13=20 AM
Subject: [FlyRotary] Re: More = MAP=20 measurement questions

Al,Rusty and All,
Excuse my ignorance here, I have = absolutely no=20 knowledge about how ECU's work. I've heard people say that it reads = MAP=20 settings - so what is a MAP, and if it's different because the = pressure is=20 different at different places in the inlet, how can the computer = calculate the=20 inlet charge and timing.
I'm confused!
George ( down under)

 

Greetings,

 

I'm working on a new = theory=20 about my low MAP reading.  The theory is that this isn't a = problem at=20 all, but rather a difference in the way it's being measured. =20

 

What=92s new about=20 this theory?  This is what I was telling you a week or two ago. = J

I = apologize for=20 lack of clarity, causing you to have to re-invent this=20 theory.

 

Al = (Also running=20 TWM TB)

 

The TWM TB has a MAP = port about=20 4 inches past the entrance of the TB throat.   That means = I'm=20 measuring the air pressure on the suction side of the largest = restriction in=20 the system (from wide open space, to 41mm tube).   Since = there's=20 no significant restriction downstream from the TB, I would = guess that I=20 could measure the MAP at the inlet of the side housing, and = wouldn't=20 find it significantly lower than what I'm seeing in the TWM=20 TB.  In other words, I'm measuring the worst possible MAP, = which=20 is the suction side.    

 

From what I = understand, the=20 typical (if there is such a thing) intake has a large TB, feeding = into an=20 open plenum, then into the smaller runners that go to the=20 engine.  If I'm not mistaken, virtually everyone is = measuring=20 their MAP in the open plenum, before the air has to enter the = smaller=20 runners to go to the engine.  In other = words, the people=20 who are reading 30" are doing it on the pressure side of the = largest=20 restriction.  

 

I could babble on = about this,=20 but my point is to ask where others are measuring their MAP (turbo = folks=20 need not apply).  You'll also have to give a general = description of=20 your intake layout.   I already know that Ed and Tracy are = using=20 the "typical" situation.  Is anyone measuring MAP in the runner = to the=20 engine?  

 

Cheers,

Rusty (duty=20 calls...)

 =20 =

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