Return-Path: Received: from relay01.roc.ny.frontiernet.net ([66.133.131.34] verified) by logan.com (CommuniGate Pro SMTP 4.1.3) with ESMTP id 2575472 for flyrotary@lancaironline.net; Wed, 10 Sep 2003 22:31:34 -0400 Received: (qmail 22752 invoked from network); 11 Sep 2003 02:31:32 -0000 Received: from unknown (HELO frontiernet.net) ([65.73.142.80]) (envelope-sender ) by relay01.roc.ny.frontiernet.net (FrontierMTA 2.3.6) with SMTP for ; 11 Sep 2003 02:31:32 -0000 Message-ID: <3F5FD0E3.8454405F@frontiernet.net> Date: Wed, 10 Sep 2003 21:33:23 -0400 From: Jim Sower X-Mailer: Mozilla 4.77 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: turbo wastegate requirements References: Content-Type: multipart/alternative; boundary="------------0FA584342AF4DE0FA9E7843D" --------------0FA584342AF4DE0FA9E7843D Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Rusty, I am totally new to all of this, but have to learn. I don't want much boost (maybe 35" or so MAP) for takeoff, but want to turbo normalize to around 15k'. I know detonation is a problem with high boost and I will have limited intercooler resources. With that in mind, how does this sound .... I would have a manual internal waste gate. The waste gate would be normally open (dumping all exhaust past the turbo). On takeoff, I would run WOT (say 29"), no boost. I could close the waste gate a little and get 33" for example for a hot day or short field. As I climb out at WOT, I gradually close the waste gate to maintain 30" MAP. Since I'm running essentially NA at low altitude (where the atmosphere is warmer) I don't need much in the way of an intercooler. As I climb and progressively close the waste gate to maintain 30", I need more intercooling, but this need is reduced by the cooler atmospheric temps. At altitude, say 15k' - 17k', 30" has me going like a bat out of hell, and the cooler air going into the system requires less intercooling. Basically, I'm running WOT most of the time and controlling the power with the waste gate, using the least amount of turbocharging I can to get the power I need. I need to know what's wrong with this line of reasoning before I start committing resources. Just a theory .... Jim S. Russell Duffy wrote: > 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, ALHi Paul,OK, here's my best turbo 101 theory: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. 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. 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. 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. 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. I hope that answered some turbo > questions.Cheers,Rusty -- Jim Sower Crossville, TN; Chapter 5 Long-EZ N83RT, Velocity N4095T --------------0FA584342AF4DE0FA9E7843D Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Rusty,
I am totally new to all of this, but have to learn.  I don't want much boost (maybe 35" or so MAP) for takeoff, but want to turbo normalize to around 15k'.  I know detonation is a problem with high boost and I will have limited intercooler resources.  With that in mind, how does this sound ....

I would have a manual internal waste gate.  The waste gate would be normally open (dumping all exhaust past the turbo).  On takeoff, I would run WOT (say 29"), no boost.  I could close the waste gate a little and get 33" for example for a hot day or short field.  As I climb out at WOT, I gradually close the waste gate to maintain 30" MAP.  Since I'm running essentially NA at low altitude (where the atmosphere is warmer) I don't need much in the way of an intercooler.  As I climb and progressively close the waste gate to maintain 30", I need more intercooling, but this need is reduced by the cooler atmospheric temps.  At altitude, say 15k' - 17k', 30" has me going like a bat out of hell, and the cooler air going into the system requires less intercooling.

Basically, I'm running WOT most of the time and controlling the power with the waste gate, using the least amount of turbocharging I can to get the power I need.  I need to know what's wrong with this line of reasoning before I start committing resources.

Just a theory .... Jim S.
 

Russell Duffy wrote:

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, ALHi Paul,OK, here's my best turbo 101 theory: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. 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. 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. 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. 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. I hope that answered some turbo questions.Cheers,Rusty

--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T
  --------------0FA584342AF4DE0FA9E7843D--