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MHerder

Joined: 11 Feb 2008
Posts: 143
Location: Fort Worth TX

Posted: Thu Nov 18, 2010 6:41 pm Post subject: Engine Shut Down

Manual on my 3300 says just turn the ignition off to shut it down...  Any reason why we should or shouldn't be shutting it off buy shutting off the fuel?

_________________
Zodiac 601 HD
Jabiru 3300
Wood Sensinich 64x47
Finally Flying

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Thu Nov 18, 2010 7:24 pm Post subject: Engine Shut Down

With a "normal" 3300 using a Bing carb, it would take a little while  

to burn the fuel in the float bowl down enough to kill the engine. If  

you had a Rotec TBI installed, shutting off the fuel supply would  

stop the engine in about 5 seconds. I'm getting to the point that I  

can shut off the fuel about 20 feet before my normal stopping (in  

front of the hangar) point, and the prop stops when I stop the plane  

from rolling.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062

Sensenich 62"x46" Wood (summer)

Electroair direct-fire ignition system

Rotec TBI-40 injection

Status: flying...1068 hrs (since 3-27-2006)

On Nov 18, 2010, at 9:41 PM, MHerder wrote:



 	  Quote: 	
		   

 <michaelherder(at)beckgroup.com>



 Manual on my 3300 says just turn the ignition off to shut it  

 down...  Any reason why we should or shouldn't be shutting it off  

 buy shutting off the fuel?



 --------

 One Rivet at a Time!





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=319979#319979

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

zeprep251(at)aol.com
Guest

Posted: Fri Nov 19, 2010 6:34 pm Post subject: Engine Shut Down

Mike,

 If you have a mixture control on your carburetor you could shut it off that way.But if you want to kill it by turning off the fuel selector,be prepared to wait for a couple minutes for the fuel bowl on the Bing to run dry. General aviation engines run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,you had to starve it of fuel to kill it.

 G.Aman Jabiru 2200A 600 hrs 

    

  

     

  

    

     

  

     

  

    --

flyadive(at)gmail.com
Guest

Posted: Sat Nov 20, 2010 2:56 pm Post subject: Engine Shut Down

G.Aman:



You are misinformed.  

 1 - IF the cylinders did "run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,"<-- Quoted from G.Amam.  You wound have a condition of PRE-IGNITION which would surely be there even a few hundred degrees still hotter DURING NORMAL RUNNING.  If this occurred you surely would have a rough running engine.  And quickly on it way to the grave.

 



2 - When you make the statement: "General aviation engines run a couple hundred degrees higher cylinder head temps", I am forced to think you are comparing aviation to automotive.  Auto engines generally run HOTTER than aircraft engines... 

 Lets define a few things here.  When you say hotter WHAT are you measuring, CHT?  

 Well there are very few air cooled auto engines out there.  Only one comes to mind, the old VW.  They were rear mounted, not a very good place for air flow cooling.  Yet, they ran very well.  So well that they have been used in aviation.  

 The newer engines of today run hotter than aviation engines for one simple reason:  They have higher compression ratios.  Most aircraft engines run 7:1, 7.5:1, 8:1. 8.5:1 and there are a few that are 9 & 10:1.  Cars start around 10:1 and go up to 12.5:1 for normal production cars.  SO, how do they stay cool running?  They are liquid cooled.  There are some aviation engines that are co-cooled -liquid and air.

 So, lets measure something else... EGT.

What is the limiting factor in leaning an engine?  Nonuniform air-fuel flow to all cylinders. I say Non Uniform because once you peak one cylinder you stop there. (I am not going to get into LOP & ROP since we are talking carborated engines.)  And deforming of the metal.  Oh, lets not forget Pre-Ignition.  Most engine savvy pilots will not go above 1450 F on EGT and the normal range is usually 1200 to 1400 F.  This is done for longevity of the engine.

 



So maybe the question should be:  Why CAN'T we shut down an aircraft engine like a car?

 Because car engines are not built like aircraft engines.  When you shut down a car engine you shut down all sorts of electrical things, Timing, Computer, Fuel Pump, Air/Fuel Valves and of course the spark. Being that there is a fuel pump and Air/Fuel Valves and most of todays cars are fuel injected... I guess you could say you are shutting the car the same as 'most' a planes. 

 



Loaded Question:  If the flash point of gas is so low, below that of internal CHT why do we not Pre-Ignition all the time?

 



Barry

 

 



 On Fri, Nov 19, 2010 at 9:27 PM,  <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

 [quote]Mike,

 If you have a mixture control on your carburetor you could shut it off that way.But if you want to kill it by turning off the fuel selector,be prepared to wait for a couple minutes for the fuel bowl on the Bing to run dry. General aviation engines run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,you had to starve it of fuel to kill it.

  G.Aman Jabiru 2200A 600 hrs 

    

  

     

  

    

     

  

     

  

    --

zeprep251(at)aol.com
Guest

Posted: Sat Nov 20, 2010 3:12 pm Post subject: Engine Shut Down

Martin,your right,I should said when the engine is hot

 My Beech 35,although injected with a mixture/ fuel cut off had a red line cyl head temp of 435F.My Jabiru runs well  under 300f, red lined at 325.Maybe the difference between cast and machined billet heads limits the temps some.Should not have an issue with moving the prop and having it start accidentally ,takes about 300rpm to fire the solid state pickup coil.but the issue was shutting the Bing equipped engine down fuel wise.My Jabiru runs on 100LL as well.

  

     Thanks G.A.

  

    

     

  

     

  

    --

zeprep251(at)aol.com
Guest

Posted: Sat Nov 20, 2010 4:25 pm Post subject: Engine Shut Down

Barry

 You are absolutely right.What could I have been thinking.

  

     

  

    

     

  

     

  

    --

BobsV35B(at)aol.com
Guest

Posted: Sat Nov 20, 2010 8:04 pm Post subject: Engine Shut Down

Good Evening All,

  

 Above all we must remember that the internal combustion engines all run by  the same rules whether they drive a lawn mower or are 3350s on a DC-7.  The  differences are in the details, but the principles do not change. EGTs are NOT  the Holy Grail and the actual temperatures do not make any difference at all.  They can serve a very important duty in telling us how our engines are  doing if we understand that they are relative and not absolute.

  

 LOP is best for longevity if you have adequate distribution. You can get  good distribution with a float carburetor or fuel injection, but it is easier to  get with fuel injection. The devil is in the details. They are all marvelous  things to behold. Don't get blinded by old wives tales. Study the available  knowledge and make your own decisions as you learn.

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 11/20/2010 9:42:35 P.M. Central Standard Time,  aerobiz1(at)gmail.com writes:

 [quote]Hi again    G.A.    



   Re shutdown :

   



   It is not so much the temperature of the cylinder head, but more the    glowing embers of carbon or even a spark plug that will keep an engine running    - albeit roughly - when you turn the ignition off. That's why we use the lean    cut-off on traditional aircraft engines.  Starve the critter.....

   



   At other times :

   



   On a Jabiru,  with its need to spin fast to get the ignition to    fire,  you would not expect a broken earth lead - making the ignition    always hot - to be so much of a danger than it would be on a Lycoming with its    impulse-coupled magneto.

   Pull through one blade, as slow as you lie, and you can easily fire the    engine up.

   



   So there is a few techniques to shutting your engine down.  If you    don't have a mixture cut-off like you would with a Rotec TBI or Aerocarb or    regular Lycoming type carb or fuel injection system, you can simply turn the    ignition off and hope that there are no glowing embers in a combustion    chamber, (if there is,  push the throttle full open - often the technique    used on Gypsy Majors in Austers and Tiger Moths) or you can turn the fuel    valve off and wait for the Bing float bowl to empty.

   Realistically, just turn the ignition off.....

   



   Martin



   On Sun, Nov 21, 2010 at 9:09 AM, <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

   [quote]     Martin,your right,I should      said when the engine is hot

My Beech 35,although injected with a mixture/      fuel cut off had a red line cyl head temp of 435F.My Jabiru runs well       under 300f, red lined at 325.Maybe the difference between cast and machined      billet heads limits the temps some.Should not have an issue with moving the      prop and having it start accidentally ,takes about 300rpm to fire the solid      state pickup coil.but the issue was shutting the Bing equipped engine down      fuel wise.My Jabiru runs on 100LL as well.



     Thanks G.A.



     

     



     



          --

aerobiz1(at)gmail.com
Guest

Posted: Sat Nov 20, 2010 9:46 pm Post subject: Engine Shut Down

Well said Bob,



Cheers

Martin



On Sun, Nov 21, 2010 at 2:01 PM,  <BobsV35B(at)aol.com (BobsV35B(at)aol.com)> wrote:

 [quote]     Good Evening All,

  

 Above all we must remember that the internal combustion engines all run by  the same rules whether they drive a lawn mower or are 3350s on a DC-7.  The  differences are in the details, but the principles do not change. EGTs are NOT  the Holy Grail and the actual temperatures do not make any difference at all.  They can serve a very important duty in telling us how our engines are  doing if we understand that they are relative and not absolute.

  

 LOP is best for longevity if you have adequate distribution. You can get  good distribution with a float carburetor or fuel injection, but it is easier to  get with fuel injection. The devil is in the details. They are all marvelous  things to behold. Don't get blinded by old wives tales. Study the available  knowledge and make your own decisions as you learn.

  

 Happy Skies,

  

 Old Bob



  

  In a message dated 11/20/2010 9:42:35 P.M. Central Standard Time,  aerobiz1(at)gmail.com (aerobiz1(at)gmail.com) writes:

 [quote]Hi again    G.A.    



   Re shutdown :

   



   It is not so much the temperature of the cylinder head, but more the    glowing embers of carbon or even a spark plug that will keep an engine running    - albeit roughly - when you turn the ignition off. That's why we use the lean    cut-off on traditional aircraft engines.  Starve the critter.....

   



   At other times :

   



   On a Jabiru,  with its need to spin fast to get the ignition to    fire,  you would not expect a broken earth lead - making the ignition    always hot - to be so much of a danger than it would be on a Lycoming with its    impulse-coupled magneto.

   Pull through one blade, as slow as you lie, and you can easily fire the    engine up.

   



   So there is a few techniques to shutting your engine down.  If you    don't have a mixture cut-off like you would with a Rotec TBI or Aerocarb or    regular Lycoming type carb or fuel injection system, you can simply turn the    ignition off and hope that there are no glowing embers in a combustion    chamber, (if there is,  push the throttle full open - often the technique    used on Gypsy Majors in Austers and Tiger Moths) or you can turn the fuel    valve off and wait for the Bing float bowl to empty.

   Realistically, just turn the ignition off.....

   



   Martin



   On Sun, Nov 21, 2010 at 9:09 AM, <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

   [quote]     Martin,your right,I should      said when the engine is hot

My Beech 35,although injected with a mixture/      fuel cut off had a red line cyl head temp of 435F.My Jabiru runs well       under 300f, red lined at 325.Maybe the difference between cast and machined      billet heads limits the temps some.Should not have an issue with moving the      prop and having it start accidentally ,takes about 300rpm to fire the solid      state pickup coil.but the issue was shutting the Bing equipped engine down      fuel wise.My Jabiru runs on 100LL as well.



     Thanks G.A.



     

     



     



          --

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Nov 21, 2010 6:53 am Post subject: Engine Shut Down

Martin:

 

You have #2 backward.  A broken P-Lead won’t allow the ignition to be grounded out...  therefore not allowing the pilot any other method of stopping the engine other than fuel starvation.  It will start just fine.

 

Noel

 

From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of Martin Hone

Sent: November 19, 2010 11:22 PM

To: jabiruengine-list(at)matronics.com

Subject: Re: Engine Shut Down



 

Hi G.A.



 



I wouldn;t be too sure about that.  I think you will find that the CHT's of any well running Continental or Lycoming are pretty much the same as for a well running Jab.  That would be between 300 and 380 degrees F in my experience.  The reason these engines use idle mixture cut-off is 

1. Because they can



2. A broken 'P' lead won't allow the engine to fire if the prop is moved



3. Highly leaded fuels provide more material that can glow in the combustion chamber and will keep the engine running-on even if the mags are switched off.



 



Cheers



 



Martin

On Sat, Nov 20, 2010 at 12:27 PM, <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

Mike,

If you have a mixture control on your carburetor you could shut it off that way.But if you want to kill it by turning off the fuel selector,be prepared to wait for a couple minutes for the fuel bowl on the Bing to run dry. General aviation engines run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,you had to starve it of fuel to kill it.

G.Aman Jabiru 2200A 600 hrs 

 



 



 



 



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Nov 21, 2010 8:01 am Post subject: Engine Shut Down

Barry:

 

I think you answered your own question.  The fuel injectors are electrically operated.  They spray a fine mist of fuel into the cylinders just before the spark is given.  Spraying cold fuel into the cylinder at that time causes the cylinder to cool a little ( may or may not be appreciable )  but also it means there isn’t any fuel there detonate.  Anti knock detectors will also adjust the timing of the fuel injection to prevent knocking.

 

Noel

 

 



Loaded Question:  If the flash point of gas is so low, below that of internal CHT why do we not Pre-Ignition all the time?



 



Barry



 



 



 



 

On Fri, Nov 19, 2010 at 9:27 PM, <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

Mike,

If you have a mixture control on your carburetor you could shut it off that way.But if you want to kill it by turning off the fuel selector,be prepared to wait for a couple minutes for the fuel bowl on the Bing to run dry. General aviation engines run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,you had to starve it of fuel to kill it.

G.Aman Jabiru 2200A 600 hrs 

 



 



 



 



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

aerobiz1(at)gmail.com
Guest

Posted: Sun Nov 21, 2010 12:25 pm Post subject: Engine Shut Down

Hi Noel,



You are correct.  What I was trying to say was that a broken 'P' lead would prevent you shutting down the engine,

Cheers and thanks

Martin

 

On Mon, Nov 22, 2010 at 12:50 AM, Noel Loveys <noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)> wrote:

[quote] 

Martin:

 

You have #2 backward.  A broken P-Lead won’t allow the ignition to be grounded out...  therefore not allowing the pilot any other method of stopping the engine other than fuel starvation.  It will start just fine. 

 

Noel

  

From: owner-jabiruengine-list-server(at)matronics.com (owner-jabiruengine-list-server(at)matronics.com) [mailto:owner-jabiruengine-list-server(at)matronics.com (owner-jabiruengine-list-server(at)matronics.com)] On Behalf Of Martin Hone

 Sent: November 19, 2010 11:22 PM

To: jabiruengine-list(at)matronics.com (jabiruengine-list(at)matronics.com)

Subject: Re: JabiruEngine-List: Engine Shut Down

 

 

Hi G.A.



 



I wouldn;t be too sure about that.  I think you will find that the CHT's of any well running Continental or Lycoming are pretty much the same as for a well running Jab.  That would be between 300 and 380 degrees F in my experience.  The reason these engines use idle mixture cut-off is  

1. Because they can



2. A broken 'P' lead won't allow the engine to fire if the prop is moved



3. Highly leaded fuels provide more material that can glow in the combustion chamber and will keep the engine running-on even if the mags are switched off. 



 



Cheers



 

Martin

On Sat, Nov 20, 2010 at 12:27 PM, <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote: 

Mike,

If you have a mixture control on your carburetor you could shut it off that way.But if you want to kill it by turning off the fuel selector,be prepared to wait for a couple minutes for the fuel bowl on the Bing to run dry. General aviation engines run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,you had to starve it of fuel to kill it.

 G.Aman Jabiru 2200A 600 hrs 

 



 



  



 

 --

flyadive(at)gmail.com
Guest

Posted: Sun Nov 21, 2010 3:40 pm Post subject: Engine Shut Down

Noel:



So how do you explain it for NON-Fuel Injected engines?

 Or engines WITHOUT anti-knock equipment?

And even those fuel injected engine WITHOUT electric injectors?

 



Remember... I said it was a LOADED QUESTION  



 

Barry



 

On Sun, Nov 21, 2010 at 10:56 AM, Noel Loveys <noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)> wrote:

 [quote]

Barry:

  

I think you answered your own question.  The fuel injectors are electrically operated.  They spray a fine mist of fuel into the cylinders just before the spark is given.  Spraying cold fuel into the cylinder at that time causes the cylinder to cool a little ( may or may not be appreciable )  but also it means there isn’t any fuel there detonate.  Anti knock detectors will also adjust the timing of the fuel injection to prevent knocking. 

 

Noel

 

  



Loaded Question:  If the flash point of gas is so low, below that of internal CHT why do we not Pre-Ignition all the time?



  



Barry



 



 



 



  

On Fri, Nov 19, 2010 at 9:27 PM, <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

 Mike,

If you have a mixture control on your carburetor you could shut it off that way.But if you want to kill it by turning off the fuel selector,be prepared to wait for a couple minutes for the fuel bowl on the Bing to run dry. General aviation engines run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,you had to starve it of fuel to kill it.

 G.Aman Jabiru 2200A 600 hrs 

 



 



  



 



--

dave.go

Joined: 20 Jul 2009
Posts: 26

Posted: Sun Nov 21, 2010 5:09 pm Post subject: Engine Shut Down

The autoignition temp of gasoline is just below 500  deg., below that it needs an ignition source. So maybe the answer is that flash  point is not autoignition temp. 

  

 [quote]    

          	  Quote: 	
		                      

Noel     

      

 

          

Loaded Question:       If the flash point of gas is so low, below that of internal CHT why do      we not Pre-Ignition all the time?

          

 

          

Barry

          

 

          

 

          

 

      

	




[b]

flyadive(at)gmail.com
Guest

Posted: Mon Nov 22, 2010 5:25 am Post subject: Engine Shut Down

Very Good Dave:



Wait for it....

Wait for it....

BUT!

The internal temps of a cylinder are higher than CHT readings.  BUT!  You do have about 60% of the question answered.

 



Think of it this way... What would cause the flash point to change?

Before I give the answer, lets try another question?

Sort of a HINT  

 



At what Temperature does water boil?

And remember this is a Loaded / Trick Question AND remember who is asking it 

Barry

=============

 On Sun, Nov 21, 2010 at 8:06 PM, Dave <d.goddard(at)ns.sympatico.ca (d.goddard(at)ns.sympatico.ca)> wrote:

[quote]        The autoignition temp of gasoline is just below 500  deg., below that it needs an ignition source. So maybe the answer is that flash  point is not autoignition temp. 

  

  	  Quote: 	
		      

          	  Quote: 	
		                      

Noel     

      

 

          

Loaded Question:       If the flash point of gas is so low, below that of internal CHT why do      we not Pre-Ignition all the time?

          

 

          

Barry

          

 

          

 

          

 

      

	








_blank">www.aeroelectric.com

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tp://forums.matronics.com

	


[b]

Kayberg(at)aol.com
Guest

Posted: Mon Nov 22, 2010 5:41 am Post subject: Engine Shut Down

At the risk of messing up a perfectly good teacher-pupil exchange along  with some drama,  could the word be "pressure'? 

  

 Pressure would increase the temperatures a la diesel.

  

 However, Jabiru engines dont seem to diesel or at least I have never heard  of one doing it.   And neither do Rotax 912s....which have even higher  compression.

  

 Tell me again why we are even bothering to discuss Ly-Con's ?

  

 Doug k.

  

  

  

 In a message dated 11/22/2010 8:25:31 A.M. Eastern Standard Time,  flyadive(at)gmail.com writes:

  	  Quote: 	
		  Very    Good Dave:    



   Wait for it....

   



   Wait for it....

   



   BUT!

   



   The internal temps of a cylinder are higher than CHT readings.  BUT!     You do have about 60% of the question answered.

   



   Think of it this way... What would cause the flash point to change?

   



   Before I give the answer, lets try another question?

   



   Sort of a HINT  

   



   At what Temperature does water boil?

   And remember this is a Loaded / Trick Question AND remember who is asking    it 

   



   Barry

   =============

   On Sun, Nov 21, 2010 at 8:06 PM, Dave <d.goddard(at)ns.sympatico.ca (d.goddard(at)ns.sympatico.ca)>    wrote:

    	  Quote: 	
		            The autoignition temp of gasoline is just below      500 deg., below that it needs    



	




	


 

  

  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Mon Nov 22, 2010 6:14 am Post subject: Engine Shut Down

Good Morning Doug k.

  

 You asked:   "Tell me again why we are even bothering to discuss  Ly-Con's ?"

  

 Because we are here to learn and all Otto Cycle engines have the same  principles of operation. If you are a trained engineer with many years of hands  on development of this art, this is probably a waste of time. However, for those  of us who are still learning, we need to understand how the problems have been  solved in the past so that we can do a better job of understanding the variances  in our Jabiru engines.

  

 All part of the learning process.

  

 Make any better sense that way?

  

 Happy Skies,

  

 Old Bob

 Legend Cub

 Jabiru 3300

 (Not mine, my granddaughter's.)

  

  In a message dated 11/22/2010 7:41:23 A.M. Central Standard Time,  Kayberg(at)aol.com writes:

  	  Quote: 	
		        At the risk of messing up a perfectly good teacher-pupil exchange along    with some drama,  could the word be "pressure'? 

    

   Pressure would increase the temperatures a la diesel.

    

   However, Jabiru engines dont seem to diesel or at least I have never    heard of one doing it.   And neither do Rotax 912s....which have    even higher compression.

    

   Tell me again why we are even bothering to discuss Ly-Con's ?

    

   Doug k.

    

    

    



	


  [quote][b]

Kayberg(at)aol.com
Guest

Posted: Mon Nov 22, 2010 6:37 am Post subject: Engine Shut Down

Old Bob, yours is a thoughtful answer.

  

 However, how far back do we need to go?   There are literally  volumes written about Otto Cycle and many many engineers who delight in sharing  their knowlege..... 

  

 And when you compare one engine design to another, many other possiblites  emerge.  For example, is the Jabiru more like your lawn mower or more like  a Lycoming?    Your lawn mower is not shut off by leaning the  mixture, just by grounding the equivalent of a P-lead.   In that sense  a Jabiru is more like your lawn mower.  (unless you have an electric  one...but that uses a switch also)

  

 I am just hoping this thread does not turn into an engineers  nightmare.

  

 Doug Koenigsberg

  

  

 In a message dated 11/22/2010 9:14:46 A.M. Eastern Standard Time,  BobsV35B(at)aol.com writes:

  	  Quote: 	
		     Good Morning Doug k.

    

   You asked:   "Tell me again why we are even bothering to    discuss Ly-Con's ?"

    

   Because we are here to learn and all Otto Cycle engines have the same    principles of operation. If you are a trained engineer with many years of    hands on development of this art, this is probably a waste of time. However,    for those of us who are still learning, we need to understand how the problems    have been solved in the past so that we can do a better job of understanding    the variances in our Jabiru engines.

    

   All part of the learning process.

    

   Make any better sense that way?

    

   Happy Skies,

    

   Old Bob

   Legend Cub

   Jabiru 3300

   (Not mine, my granddaughter's.)

    

      In a message dated 11/22/2010 



	


 

  

  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Mon Nov 22, 2010 7:05 am Post subject: Engine Shut Down

Good Morning Doug,

  

 Agreed! In fact we often err in many operations because "It has always been  done that way."

  

 Shutting down the engine by taking away it's fuel is just one of those  habits that do not necessarily serve any real purpose. When doing repetitive  flights such as passenger hops and Young Eagle flights some engines start a  lot easier if the switch is used for that purpose. I find no heartburn at all  when I shut down the Jabiru by turning off the ignition switch.

  

 We could probably write volumes about all of the Old Wives Tales concerning  piston engine operation.

  

 All part of our continuing education!

  

 Happy Skies,

  

 Old Bob

  

 PS As for the lawn mower and Lycoming, they both suck, push, bang, and  blow! <G>

  

  In a message dated 11/22/2010 8:38:05 A.M. Central Standard Time,  Kayberg(at)aol.com writes:

  	  Quote: 	
		        Old Bob, yours is a thoughtful answer.

    

   However, how far back do we need to go?   There are literally    volumes written about Otto Cycle and many many engineers who delight in    sharing their knowlege..... 

    

   And when you compare one engine design to another, many other possiblites    emerge.  For example, is the Jabiru more like your lawn mower or more    like a Lycoming?    Your lawn mower is not shut off by leaning    the mixture, just by grounding the equivalent of a P-lead.   In that    sense a Jabiru is more like your lawn mower.  (unless you have an    electric one...but that uses a switch also)

    

   I am just hoping this thread does not turn into an engineers    nightmare.

    

   Doug Koenigsberg

    



	


  [quote][b]

flyadive(at)gmail.com
Guest

Posted: Mon Nov 22, 2010 10:00 am Post subject: Engine Shut Down

BINGO DOUG - BINGO!



Go to the head of the class  

 



Pressure increases the flash point.



 

Barry



  [quote][b]

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Nov 23, 2010 8:50 am Post subject: Engine Shut Down

Ok but you did ask about fuel injected engines..

 

With non-injected engines they will “ping” just about all the time but you will only be able to notice it when the rpm and load are in specific quantities.  For instance a friend of mine many years ago had a Ford 500 with the 390 4bbl., dual low resistance exhausts and mo doubt a few other goodies on it.  It had a real problem for we idiot speed demons, it backfired like a mule after 90 mph.  That was long before it really got producing what it could.  After trying everything to stop the backfiring my friend finally got rid of the car.  Several years later the Royal Newfoundland Constabulary had the same problem with a factory built hotrod they got from GM.  The Constab, had their own fuel supply so they knew it was high octane.  GM technicians from the factory spent two weeks working on the car until they had exhausted ( pardon the pun) every possibility.  One of the technicians then sent a sample of the fuel back to GM for a flash test.... It was low-low octane.   The Constabulary then decided to test all the high octane tanks in the area, of some fifty tanks tested only one actually had high octane fuel.  The Constabulary then charged their test lab with fixing octane numbers and sent notification to all the oil companies servicing the province with warning that their fuel would be tested on a regular basis.  The reply they got form their supplier was that they would no longer do octane testing for the Constabulary.

 

The reason conventionally aspirated direct drive aircraft engines get away, most of the time, with lower octane fuel is they are specifically tuned to operate at high throttle settings for extended periods of time.  They are also designed to mostly work at lower rpm with a much flatter torque curve than a conventional auto engine.  Of course those engines are only certified to use specific fuels so the question is a bit mute.   They are also generally high displacement for the power they deliver.  The interesting thing with the big radials is they develop so much heat they actually change shape in different phases of flight.  Descent is a particularly touchy time as it is dangerous to allow the engine to cool too much as you may need the power on short notice and drawing power form a cold engine is a recipe for not too much fun.

 

 There are also many large air-cooled gear driven radial engines which rev to the territory of the 912 and it was not uncommon for them to blow jugs on flights even with the certified fuels.  In fact there used to be a running joke that you could always tell the mechanic at an airport because he was the one who drove the biggest, most expensive or fastest car.  He made his money replacing cylinders on corn cob radials. ;->

 

Back from the diversion....  The engines we use (912 UL etc.) are designed to operate efficiently in the extended rpm envelope using fuels of lower octane.  Those engines which use higher compression ratios and/or turbo charging ( 914 etc.) are designed to operate on higher octane no lead auto fuels.  This is great as long as such fuels are available.   The problem we are now coming into is the extended use of ethanol, both as an oxidizer and an octane booster...  don’t start me on that one!

 

Noel

 

From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of FLYaDIVE

Sent: November 21, 2010 8:08 PM

To: jabiruengine-list(at)matronics.com

Subject: Re: Engine Shut Down



 

Noel:

 



So how do you explain it for NON-Fuel Injected engines?



Or engines WITHOUT anti-knock equipment?



And even those fuel injected engine WITHOUT electric injectors?



 



Remember... I said it was a LOADED QUESTION  



 



Barry



 



 



 

On Sun, Nov 21, 2010 at 10:56 AM, Noel Loveys <noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)> wrote:

Barry:

 

I think you answered your own question.  The fuel injectors are electrically operated.  They spray a fine mist of fuel into the cylinders just before the spark is given.  Spraying cold fuel into the cylinder at that time causes the cylinder to cool a little ( may or may not be appreciable )  but also it means there isn’t any fuel there detonate.  Anti knock detectors will also adjust the timing of the fuel injection to prevent knocking.

 

Noel

 

 



Loaded Question:  If the flash point of gas is so low, below that of internal CHT why do we not Pre-Ignition all the time?



 



Barry



 



 



 



 

On Fri, Nov 19, 2010 at 9:27 PM, <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

Mike,

If you have a mixture control on your carburetor you could shut it off that way.But if you want to kill it by turning off the fuel selector,be prepared to wait for a couple minutes for the fuel bowl on the Bing to run dry. General aviation engines run a couple hundred degrees higher cylinder head temps and would run on with out spark ignition,you had to starve it of fuel to kill it.

G.Aman Jabiru 2200A 600 hrs 

 



 



 



 



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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