Return-Path: <13brv3@bellsouth.net> Received: from imf16aec.mail.bellsouth.net ([205.152.59.64] verified) by logan.com (CommuniGate Pro SMTP 4.1.3) with ESMTP id 2574877 for flyrotary@lancaironline.net; Wed, 10 Sep 2003 12:05:29 -0400 Received: from rad ([68.212.14.21]) by imf16aec.mail.bellsouth.net (InterMail vM.5.01.05.27 201-253-122-126-127-20021220) with ESMTP id <20030910160528.FTGT21511.imf16aec.mail.bellsouth.net@rad> for ; Wed, 10 Sep 2003 12:05:28 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] turbo wastegate requirements Date: Wed, 10 Sep 2003 11:05:27 -0500 Message-ID: <001e01c377b5$59e60aa0$0201a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001F_01C3778B.711002A0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_001F_01C3778B.711002A0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable I was reading the installation and operation manual that came with my MicroTech electronic engine management system, and under "setting up" = there is a section entitled BstCUT, which says "This feature prevents turbo engines from overboosting by cutting all fuel supply when bost pressure exceeds the limit set in theBSTcut screen, i.e: if you set this value = to 10 psi, all fuel supply will be immediately shut off when boost is 11 psi = or higher." Does this sound like a useful tool in installing and setting = up a turbo on my 13b? Please don't flame me, as I know less about turbos = than I know about understanding women. Does this mean I would not need a wastegate? Thanks in advance for your replies. Paul Conner, Mobile, AL = =20 Hi Paul,=20 =20 OK, here's my best turbo 101 theory: =20 In all stock turbo applications, there's a wastegate to control the = boost. This is just a "valve" of sorts to let exhaust gas go around the turbine (less boost), rather than through it (more boost). It can be built into = the turbo housing as in most stock applications, and called an internal wastegate, or it can be a separate unit called an external wastegate. = This valve is physically actuated by the wastegate actuator, which is a big vacuum pot looking thing with a long arm that connects to the wastegate lever. The actuator itself has a spring that's set to a specific = pressure, which is usually below the max pressure that you want. In other words, = if you plan to run 10 psi of boost, the spring might be 6 psi. The = actuator is generally controlled by pressure on a hose from the turbo compressor = itself. This hose can also be Teed into an electronic control of some type. =20 =20 Basically, here's how it works. Say you have a turbo, with an internal wastegate, and an actuator with a spring pressure of 6 psi. The = wastegate is held closed by the spring, which causes all the exhaust to flow = through the turbine, and makes maximum boost. At idle and low throttle = settings, there isn't enough exhaust flow to produce any significant boost, so the wastegate stays closed. When you open the throttle, the extra exhaust = flow spins up the turbine, and starts producing boost on the compressor side. = As the boost increases the pressure increases in the actuator line as well. Once the pressure in the line gets higher than the spring pressure in = the actuator (6psi for our example) the pressure starts acting against the spring in the actuator to open the wastegate. As the wastegate opens, = less exhaust flows through the compressor, which reduces the boost. If the wastegate opens too much, the boost is reduced below 6 psi, and the = spring is able to close the wastegate again, which starts the cycle over. Keep = in mind that this isn't a binary, open/closed operation in reality, the = amount the wastegate is open varies the boost, accordingly. The spring in the actuator also doesn't just snap completely open when the boost hits 6.1 = psi. It starts to open at 6, and opens more at 7, more at 8, etc. =20 =20 That was the most basic (automatic) way of controlling the wastegate. Remember that you wanted 10 psi, so if the wastegate is big enough, and = the spring is set to 6 psi, how will you ever get there? The answer is to = bleed some of the boost out of the wastegate actuator pressure line. You can = do something as simple as putting a needle valve in the boost actuator = line, and open it some. By varying the opening amount, you're changing the pressure that the actuator sees. Now you can have 10 psi of boost, by allowing a 4 psi leak of the air in the actuator line. (Turbo 201 = begins here) In stock vehicles, you tee this line into a solenoid, and let the computer control the opening and closing of the solenoid. Since this is = a binary open/closed situation, the computer sends a square wave pulse to = the solenoid, and varies the pulse width to control the amount of time the solenoid is open. =20 =20 Now, as for the question of using the boost fuel cut. This is a safety device, and not a controller of any sort. You do not ever want this to = have to kick in. Imagine you've just lifted off, running full throttle (the = only time you're going to have too much boost), and your engine quits. The computer saved your engine, while trying to kill you. IF you can verify = how this feature behaves, and test it on the ground, it might be worth = setting up, otherwise, I'd leave it off, or set it to something like 30 psi so = it never comes on. I would want to know how quickly it reacts. In other words, say you set it at 5 psi, then go to full throttle where it sees 6 = psi almost immediately. It will cut the fuel, but when does it turn it back = on? Boost will immediately drop due to loss of power, so does it come back = on when it gets back below 5 psi? If so, you could use it, but would have = to teach yourself to react to an engine failure by pulling the throttle = back some. =20 =20 One other word about wastegates. You can control the wastegate = manually, as I am trying to do. I just have a cable running to the wastegate lever, rather than actually having an actuator. Depending on how much boost = you need, and how effective your wastegate is, you could possibly just wire = the wastegate wide open. For example, I know that I can make more than 3 = psi of boost (over ambient pressure) with the wastegate wide open, because = that's where mine is, and I have a relief valve that's dumping the excess above that. The relief valve is also a safety item, that I'll eventually get = rid of, but I'm using it now to keep me from blowing the engine while I = prove that I can control boost via the throttle. So far, boost is easily controllable with the throttle alone, though it does add to the = workload. =20 =20 I hope that answered some turbo questions. =20 Cheers, Rusty =20 ------=_NextPart_000_001F_01C3778B.711002A0 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message
I was reading the installation = and operation=20 manual that came with my MicroTech electronic engine management system, = and=20 under "setting up" there is a section entitled BstCUT,  which says = "This=20 feature prevents turbo engines from overboosting by cutting all fuel = supply when=20 bost pressure exceeds the limit set in theBSTcut screen, i.e:  if = you set=20 this value to 10 psi, all fuel supply will be immediately shut off when = boost is=20 11 psi or higher."  Does this sound like a useful tool in = installing and=20 setting up a turbo on my 13b?  Please don't flame me, as I know = less about=20 turbos than I know about understanding women.  Does this mean I = would not=20 need a wastegate?  Thanks in advance for your replies.  Paul = Conner,=20 Mobile, AL 
 
Hi = Paul, 
 
OK, here's my best turbo 101=20 theory:
 
In all stock turbo applications, there's a = wastegate to=20 control the boost.  This is just a "valve" of sorts to let exhaust = gas go=20 around the turbine (less boost), rather than through it (more = boost).  It=20 can be built into the turbo housing as in most stock applications, and = called an=20 internal wastegate, or it can be a separate unit called an external=20 wastegate.  This valve is physically actuated by the wastegate = actuator,=20 which is a big vacuum pot looking thing with a long arm that connects to = the=20 wastegate lever.   The actuator itself has a spring that's set = to a=20 specific pressure, which is usually below the max pressure that you = want. =20 In other words, if you plan to run 10 psi of boost, the spring might be = 6=20 psi.  The actuator is generally controlled by pressure on a hose = from the=20 turbo compressor itself.  This hose can also be Teed into an = electronic=20 control of some type. 
 
Basically, here's how it works.  Say you = have a=20 turbo, with an internal wastegate, and an actuator with a spring = pressure of 6=20 psi.  The wastegate is held closed by the spring, which causes all = the=20 exhaust to flow through the turbine, and makes maximum = boost.  At idle=20 and low throttle settings, there isn't enough exhaust flow to produce = any=20 significant boost, so the wastegate stays closed.  When you open = the=20 throttle, the extra exhaust flow spins up the turbine, and starts = producing=20 boost on the compressor side.  As the boost increases the pressure=20 increases in the actuator line as well.  Once the pressure in the = line gets=20 higher than the spring pressure in the actuator (6psi for our example) = the=20 pressure starts acting against the spring in the actuator to open = the=20 wastegate.  As the wastegate opens, less exhaust flows through the=20 compressor, which reduces the boost.  If the wastegate opens too = much, the=20 boost is reduced below 6 psi, and the spring is able to close=20 the wastegate again, which starts the cycle over.  Keep = in mind=20 that this isn't a binary, open/closed operation in reality, the amount = the=20 wastegate is open varies the boost, accordingly.  The spring in the = actuator also doesn't just snap completely open when the boost = hits 6.1=20 psi.  It starts to open at 6, and opens more at 7, more at 8,=20 etc.  
 
That was the most basic (automatic) way = of=20 controlling the wastegate.  Remember that you wanted 10 psi, = so if the=20 wastegate is big enough, and the spring is set to 6 psi, how will you = ever get=20 there?  The answer is to bleed some of the boost out of the = wastegate=20 actuator pressure line.  You can do something as simple as putting = a needle=20 valve in the boost actuator line, and open it some.  By varying the = opening=20 amount, you're changing the pressure that the actuator = sees.  Now you=20 can have 10 psi of boost, by allowing a 4 psi leak of the air = in the=20 actuator line.  (Turbo 201 begins here) In stock = vehicles, you=20 tee this line into a solenoid, and let the computer control the opening = and=20 closing of the solenoid.  Since this is a binary open/closed = situation, the=20 computer sends a square wave pulse to the solenoid, and varies the pulse = width=20 to control the amount of time the solenoid is open. =20
 
Now, as for the question of using the boost = fuel=20 cut.  This is a safety device, and not a controller of any = sort.  You=20 do not ever want this to have to kick in.  Imagine you've just = lifted off,=20 running full throttle (the only time you're going to have too much = boost), and=20 your engine quits.  The computer saved your engine, while trying=20 to kill you.  IF you can verify how this feature behaves,=20 and test it on the ground, it might be worth setting up, otherwise, = I'd=20 leave it off, or set it to something like 30 psi so it never comes = on. =20  I would want to know how quickly it reacts.  In other words, = say you=20 set it at 5 psi, then go to full throttle where it sees 6 psi almost=20 immediately.  It will cut the fuel, but when does it turn it back = on? =20 Boost will immediately drop due to loss of power, so does it come back = on when=20 it gets back below 5 psi?  If so, you could use it, but would have = to teach=20 yourself to react to an engine failure by pulling the throttle back = some. =20
 
One other word about wastegates.  You = can control=20 the wastegate manually, as I am trying to do.  I just have a cable = running=20 to the wastegate lever, rather than actually having an actuator.  = Depending=20 on how much boost you need, and how effective your wastegate is, you = could=20 possibly just wire the wastegate wide open.  For example, I know = that I can=20 make more than 3 psi of boost (over ambient pressure) with the = wastegate=20 wide open, because that's where mine is, and I have a relief valve = that's=20 dumping the excess above that.  The relief valve is also a safety = item,=20 that I'll eventually get rid of, but I'm using it now to keep me from = blowing=20 the engine while I prove that I can control boost via the = throttle.  So=20 far, boost is easily controllable with the throttle alone, though it = does add to=20 the workload. 
 
I hope that answered some turbo=20 questions.
 
Cheers,
Rusty
 
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