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low compression on Jabiru engine using AVGAS

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info(at)jabiru.cl
Guest

Posted: Wed Oct 20, 2010 5:39 pm Post subject: low compression on Jabiru engine using AVGAS

Hi group, I have 3 engines (3 different owners in different cities) that are running on avgas 100/130 in Chile, that after 80 hours are with low compression on 2 or more cylinders. Have some of you any experience with same issue? 2 of these engines are flying in J450 and J430 and one of them is mounted in a Jabiru UL (2200).  

Please any commends will be appreciated,  

   

Christian  

       [quote][b]

flyadive(at)gmail.com
Guest

Posted: Wed Oct 20, 2010 7:09 pm Post subject: low compression on Jabiru engine using AVGAS

Christian:



There is a VERY good chance you are experiencing the same problems MANY engines here in the USA are experiencing while running on 100LL.  100LL is really not Low Lead at all.  It is four times the lead as the old AvGas 80.

 Since you are having low compression I would bet that they are experiencing lead/coke build up in the valve stems.

If the build up goes untreated the valve will stick in the down (open) position and if the valve - cylinder clearance is an interference fit they will be spitting out valve parts.  AND even if it is not an interference fit, the compression will go to zero and still again they will be looking for an emergency field and new engine parts.

 



The options are:

Use TCP in the fuel to reduce lead build up

LEAN AGGRESSIVELY - ALL THE TIMES -- Even when taxing.

Use AUTO - MoGas or a mixture of MoGas & AvGas.  Just keep the octane where needed.

 1 hour flight before every oil change put in one quart of MMO (Marvell Mystery Oil) - This helps clean the build up.

Now, these suggestion come with the limited information you gave.  We don't know how the engines are being run.

 The time between oil changes.

The type of oil being used.

The quality of the gas and at least a dozen more items.

Since you identified that the engines have low compression - Have you identified where they are leaking from?  

 Valves or Rings?

Any gasket leaks?

Fill in the blanks on the above questions and I'll try to diagnose.

GOOD LUCK,

Barry

 



On Wed, Oct 20, 2010 at 9:36 PM, Jabiru Chile <info(at)jabiru.cl (info(at)jabiru.cl)> wrote:

[quote]                 

Hi group, I have 3 engines (3 different owners in different cities) that are running on avgas 100/130 in Chile, that after 80 hours are with low compression on 2 or more cylinders. Have some of you any experience with same issue? 2 of these engines are flying in J450 and J430 and one of them is mounted in a Jabiru UL (2200).  

Please any commends will be appreciated,  

   

Christian



[b]

plus2s

Joined: 30 Nov 2006
Posts: 65
Location: NEW ZEALAND

Posted: Thu Oct 21, 2010 1:37 am Post subject: low compression on Jabiru engine using AVGAS

Hi Christian



We have found that the high lead content of 100/130 can cause the top ring to get tight in the ring groove. There is some interesting facts re the different fuels in the January 2010 Jabba Chat on the Jabiru Au web site. It is also important to make sure the engine is not running lean. ie has the latest recommended jetting. Of course that can vary if the engines aren't in Jabiru airframes. It is also possible to get lead deposits stuck under a valve.



Will be interested to see what you find.



Regards



Keith



--- On Thu, 21/10/10, Jabiru Chile <info(at)jabiru.cl> wrote:

 	  Quote: 	
		  

From: Jabiru Chile <info(at)jabiru.cl>

Subject: low compression on Jabiru engine using AVGAS

To:  jabiruengine-list(at)matronics.com

Date: Thursday, 21, October, 2010, 2:36 PM



                    

Hi group, I have 3 engines (3 different owners in different cities) that are running on avgas 100/130 in  Chile , that after 80 hours are with low compression on 2 or more cylinders. Have some of you any experience with same issue? 2 of these engines are flying in J450 and J430 and one of them is mounted in a Jabiru UL (2200).   

Please any commends will be appreciated,   

     

Christian   

        	  Quote: 	
		  f="http://www.matronics.com/Navigator?JabiruEngine-List">http://www.matro="nofollow" target="_blank" href="http://forums.matronics.com">http://www.matronics.com/contribution">http://www.matronics.com/contribution============


	


	
  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Thu Oct 21, 2010 6:24 am Post subject: low compression on Jabiru engine using AVGAS

Good Morning Keith,

  

 You wrote: "It is also important to make sure the engine is not running  lean"

  

 Could you expand on this statement a bit? At lower power settings, lean is  the best place to be and at high power settings it is not. In either case, lean  is always relative and it should be on the lean side or on the rich side  relative to some operating parameter.

  

 Don't you agree?

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 10/21/2010 4:37:22 A.M. Central Daylight Time,  kpickford(at)xtra.co.nz writes:

  	  Quote: 	
		                      Hi Christian



We have found that the high lead          content of 100/130 can cause the top ring to get tight in the ring          groove. There is some interesting facts re the different fuels in the          January 2010 Jabba Chat on the Jabiru Au web site. It is also important          to make sure the engine is not running lean. ie has the latest          recommended jetting. Of course that can vary if the engines aren't in          Jabiru airframes. It is also possible to get lead deposits stuck under a          valve.



Will be interested to see what you          find.



Regards



Keith



--- On Thu, 21/10/10, Jabiru          Chile <info(at)jabiru.cl> wrote:

          	  Quote: 	
		  

From:            Jabiru Chile <info(at)jabiru.cl>

Subject: JabiruEngine-List: low            compression on Jabiru engine using AVGAS

To:            jabiruengine-list(at)matronics.com

Date: Thursday, 21, October, 2010,            2:36 PM



                                               

Hi group, I have 3 engines            (3 different owners in different cities) that are running on avgas            100/130 in Chile , that after 80 hours are with low compression on 2            or more cylinders. Have some of you any experience with same issue? 2            of these engines are flying in J450 and J430 and one of them is            mounted in a Jabiru UL (2200).           

Please any commends will            be appreciated,           

            

Christian

 	  Quote: 	
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  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Thu Oct 21, 2010 6:39 am Post subject: low compression on Jabiru engine using AVGAS

Good Morning Barry,

  

 The last time I flew down south of the border, 100/130 AVGAS was still the  old mix and it had about three times the lead of 100LL. That means it has about  twelve times the lead of the old 80 Octane AVGAS. Really bad stuff for a  relatively low compression engine.

  

 Could anyone tell us whether that is still the case?

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 10/20/2010 10:10:11 P.M. Central Daylight Time,  flyadive(at)gmail.com writes:

  	  Quote: 	
		  Christian:    



   There is a VERY good chance you are experiencing the same    problems MANY engines here in the USA are experiencing while running on    100LL.  100LL is really not Low Lead at all.  It is four    times the lead as the old AvGas 80.

   Since you are having low compression I would bet that they    are experiencing lead/coke build up in the valve stems.

   If the build up goes untreated the valve will stick in the down    (open) position and if the valve - cylinder clearance is    an interference fit they will be spitting out valve parts.  AND    even if it is not an interference fit, the compression will go to    zero and still again they will be looking for an emergency field and new    engine parts.

   



   The options are:

   Use TCP in the fuel to reduce lead build up

   LEAN AGGRESSIVELY - ALL THE TIMES -- Even when taxing.

   Use AUTO - MoGas or a mixture of MoGas & AvGas.  Just keep the    octane where needed.

   1 hour flight before every oil change put in one quart of MMO (Marvell    Mystery Oil) - This helps clean the build up.

   



   Now, these suggestion come with the limited information you gave.     We don't know how the engines are being run.

   The time between oil changes.

   The type of oil being used.

   The quality of the gas and at least a dozen more    items.

   



   Since you identified that the engines have low compression - Have you    identified where they are leaking from?  

   Valves or Rings?

   Any gasket leaks?

   



   Fill in the blanks on the above questions and I'll try    to diagnose.

   



   GOOD LUCK,

   Barry

   



   



   



   



   



   On Wed, Oct 20, 2010 at 9:36 PM, Jabiru Chile <info(at)jabiru.cl (info(at)jabiru.cl)> wrote:

    	  Quote: 	
		                 

Hi group, I have 3 engines (3      different owners in different cities) that are running on avgas 100/130 in      Chile, that after 80 hours are with low compression on 2 or more cylinders.      Have some of you any experience with same issue? 2 of these engines are      flying in J450 and J430 and one of them is mounted in a Jabiru UL      (2200).     

Please any commends will be      appreciated,     

      

Christian







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

List href="http://www.matronics.com/Navigator?JabiruEngine-List">http://www.matronics.com/Navigator?JabiruEngine-List

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

ms.matronics.com/">http://forums.matronics.com

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

tp://www.matronics.com/contribution">http://www.matronics.com/contribution

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



	
	


  [quote][b]

plus2s

Joined: 30 Nov 2006
Posts: 65
Location: NEW ZEALAND

Posted: Thu Oct 21, 2010 2:57 pm Post subject: low compression on Jabiru engine using AVGAS

Hi Bob



we had a engine "Blow" at 500 hours that was running lean. An early hydraulic lifter 2200 engine.



Jabiru bought out a revised tuning (jetting) for them.



Regards



Keith



--- On Fri, 22/10/10, BobsV35B(at)aol.com <BobsV35B(at)aol.com> wrote:



 	  Quote: 	
		   From: BobsV35B(at)aol.com <BobsV35B(at)aol.com>

 Subject: Re: low compression on Jabiru engine using AVGAS

 To: jabiruengine-list(at)matronics.com

 Date: Friday, 22, October, 2010, 3:20 AM

 

 

  

  

 

 Good Morning Keith,

  

 You wrote: "It is also important to make sure the

 engine is not running 

 lean"

  

 Could you expand on this statement a bit? At lower

 power settings, lean is 

 the best place to be and at high power settings it is not.

 In either case, lean 

 is always relative and it should be on the lean side or on

 the rich side 

 relative to some operating parameter.

  

 Don't you agree?

  

 Happy Skies,

  

 Old Bob

  

 

 In a message dated 10/21/2010 4:37:22 A.M. Central

 Daylight Time, 

 kpickford(at)xtra.co.nz writes:

 

   

     

     

       Hi Christian

 

 We have found that the high lead 

         content of 100/130 can cause the top ring to get

 tight in the ring 

         groove. There is some interesting facts re the

 different fuels in the 

         January 2010 Jabba Chat on the Jabiru Au web site.

 It is also important 

         to make sure the engine is not running lean. ie has

 the latest 

         recommended jetting. Of course that can vary if the

 engines aren't in 

         Jabiru airframes. It is also possible to get lead

 deposits stuck under a 

         valve.

 

 Will be interested to see what you 

         find.

 

 Regards

 

 Keith

 

 --- On Thu, 21/10/10, Jabiru 

         Chile <info(at)jabiru.cl> wrote:

 

         

 From: 

           Jabiru Chile <info(at)jabiru.cl>

 Subject: low 

           compression on Jabiru engine using AVGAS

 To: 

           jabiruengine-list(at)matronics.com

 Date: Thursday, 21, October, 2010, 

           2:36 PM

 

 

           

           

 

 

 

           

           Hi group, I have 3

 engines 

           (3 different owners in different cities) that are

 running on avgas 

           100/130 in Chile , that after 80 hours are with

 low compression on 2 

           or more cylinders. Have some of you any

 experience with same issue? 2 

           of these engines are flying in J450 and J430 and

 one of them is 

           mounted in a Jabiru UL (2200).

           Please any

 commends will 

           be appreciated,

            

           Christianf="http://www.matronics.com/Navigator?JabiruEngine-List">http://www.matro="nofollow"

 target="_blank"

 href="http://forums.matronics.com">http://www.matronics.com/contribution">http://www.matronics.com/contribution============

 

 

 

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

 List

 href="http://www.matronics.com/Navigator?JabiruEngine-List">http://www.matronics.com/Navigator?JabiruEngine-List

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

 ms.matronics.com/">http://forums.matronics.com

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

 tp://www.matronics.com/contribution">http://www.matronics.com/contribution

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

info(at)jabiru.cl
Guest

Posted: Thu Oct 21, 2010 3:06 pm Post subject: low compression on Jabiru engine using AVGAS

Thank you Barry,  

Thank you for the info. The info I can share is:  

Engine (J3300 in J450), about 80 hours since new, using AVGAS100/130 since first start in Chile, Oil used Shell aviation oil multigrade, Airplane build to Jabiru standards with no extras other that ones offered by Jabiru, Jabiru standard prop for this engine/airplane config., maintenance of engine according to engine manual (oil changes, spark replace, oil filter, etc). Leak are in two cylinders (more than others) and came from the exhaust valves, but these two low compression cylinders where checked and the inside of the cylinders looks not good with some scratches, probably done by the rest of lead/coke build up in the combustion chamber or in top of the pistons. Airplane is located 1000 km from Santiago and is flying by a Flying Club.  

Engine (J3300 in J430), about 80 hours since the pilot report low compression 2 month ago. Same configuration than the above airplane, one owner, flying near Santiago, and the problem found was in the exhaust valves, but this airplane/engine have the economy tunning kit that Jabiru offers for this engines.  

Engine (J2200 in Jabiru UL), after a change of engine in the airplane, due the original engine was from 1998 with 800 hours, was not worth to make an overhaul, so the owner opt to change engine for a new model with longer overhaul, hydraulic lifters, etc., but after about 70 hours and after a maintenance check the mechanic found that the engine was not running good and make a compression check. Same problem than above engines. Exhaust valves not sealing, and after a clean up, was again with normal compression and now the owner decide to use automobile gas 97 oct rating, unleaded.  

I have also about 10 engines in Ultralight airplanes flying with automobile gas 97 oct, and some of them with more than 800 hours, with compressions like a new engine, so the AVGAS here in my conclusion is not the best for Jabiru engines.  

   

Thank you all for your support and info.  

   

Regards,  

   

Christian   

         

  

De: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] En nombre de FLYaDIVE

 Enviado el: Thursday, October 21, 2010 12:07 AM

 Para: jabiruengine-list(at)matronics.com

 Asunto: Re: low compression on Jabiru engine using AVGAS  

  

   

Christian:    

   

    

There is a VERY good chance you are experiencing the same problems MANY engines here in the USA are experiencing while running on 100LL.  100LL is really not Low Lead at all.  It is four times the lead as the old AvGas 80.  

    

Since you are having low compression I would bet that they are experiencing lead/coke build up in the valve stems.  

    

If the build up goes untreated the valve will stick in the down (open) position and if the valve - cylinder clearance is an interference fit they will be spitting out valve parts.  AND even if it is not an interference fit, the compression will go to zero and still again they will be looking for an emergency field and new engine parts.  

    

   

    

The options are:  

    

Use TCP in the fuel to reduce lead build up  

    

LEAN AGGRESSIVELY - ALL THE TIMES -- Even when taxing.  

    

Use AUTO - MoGas or a mixture of MoGas & AvGas.  Just keep the octane where needed.  

    

1 hour flight before every oil change put in one quart of MMO (Marvell Mystery Oil) - This helps clean the build up.  

    

   

    

Now, these suggestion come with the limited information you gave.  We don't know how the engines are being run.  

    

The time between oil changes.  

    

The type of oil being used.  

    

The quality of the gas and at least a dozen more items.  

    

   

    

Since you identified that the engines have low compression - Have you identified where they are leaking from?    

    

Valves or Rings?  

    

Any gasket leaks?  

    

   

    

Fill in the blanks on the above questions and I'll try to diagnose.  

    

   

    

GOOD LUCK,  

    

Barry  

    

   

    

   

    

   

    

   

    

     

On Wed, Oct 20, 2010 at 9:36 PM, Jabiru Chile <info(at)jabiru.cl (info(at)jabiru.cl)> wrote:      

Hi group, I have 3 engines (3 different owners in different cities) that are running on avgas 100/130 in Chile, that after 80 hours are with low compression on 2 or more cylinders. Have some of you any experience with same issue? 2 of these engines are flying in J450 and J430 and one of them is mounted in a Jabiru UL (2200).  

Please any commends will be appreciated,  

   

Christian  

  

  

  

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       [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Thu Oct 21, 2010 4:45 pm Post subject: low compression on Jabiru engine using AVGAS

Good Evening Keith,

  

 I can understand that if it was running "Lean" when it should have been not  running "Lean", but that still does not answer the question. Lean in relation to  what?

  

 And, at what power settings?

  

 Makes a very big difference.

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 10/21/2010 5:57:40 P.M. Central Daylight Time,  kpickford(at)xtra.co.nz writes:

  	  Quote: 	
		  -->    JabiruEngine-List message posted by: Keith Pickford    <kpickford(at)xtra.co.nz>

Hi Bob



we had a engine "Blow"    at 500 hours that was running lean. An early hydraulic lifter 2200    engine.



Jabiru bought out a revised tuning (jetting) for    them.



Regards



Keith



--- On Fri, 22/10/10,    BobsV35B(at)aol.com <BobsV35B(at)aol.com> wrote:



 	  Quote: 	
		   From:    BobsV35B(at)aol.com <BobsV35B(at)aol.com>

 Subject: Re:    low compression on Jabiru engine using AVGAS

 To:    jabiruengine-list(at)matronics.com

 Date: Friday, 22, October, 2010, 3:20    AM

 

 

  

  

 

 Good    Morning Keith,

  

 You wrote: "It is also important to make    sure the

 engine is not running 

 lean"

  

    Could you expand on this statement a bit? At lower

 power settings,    lean is 

 the best place to be and at high power settings it is    not.

 In either case, lean 

 is always relative and it should be    on the lean side or on

 the rich side 

 relative to some    operating parameter.

  

 Don't you agree?

     

 Happy Skies,

  

 Old    Bob

  

	

	


  [quote][b]

Kayberg(at)aol.com
Guest

Posted: Fri Oct 22, 2010 7:08 am Post subject: low compression on Jabiru engine using AVGAS

Barry,

  

 Do you have significant experience with Jabiru engines?   Your  comments would indicate a  background in other engines (Ly-Con) which are  not  the same as a Jabiru.

  

 For example, the carbs are not leanable, nor is leaning suggested by  Jabiru

  

 Further, since the Jab engines have such a low oil volume, your Marvel  Mystery Oil suggestion is not a good one, and  might generate a whole other  set of problems.

  

 Doug Koenigsberg

  

  

  

 In a message dated 10/20/2010 11:10:11 P.M. Eastern Daylight Time,  flyadive(at)gmail.com writes:

  	  Quote: 	
		  Christian:    



   There is a VERY good chance you are experiencing the same    problems MANY engines here in the USA are experiencing while running on    100LL.  100LL is really not Low Lead at all.  It is four    times the lead as the old AvGas 80.

   Since you are having low compression I would bet that they    are experiencing lead/coke build up in the valve stems.

   If the build up goes untreated the valve will stick in the down    (open) position and if the valve - cylinder clearance is    an interference fit they will be spitting out valve parts.  AND    even if it is not an interference fit, the compression will go to    zero and still again they will be looking for an emergency field and new    engine parts.

   



   The options are:

   Use TCP in the fuel to reduce lead build up

   LEAN AGGRESSIVELY - ALL THE TIMES -- Even when taxing.

   Use AUTO - MoGas or a mixture of MoGas & AvGas.  Just keep the    octane where needed.

   1 hour flight before every oil change put in one quart of MMO (Marvell    Mystery Oil) - This helps clean the build up.

   



   Now, these suggestion come with the limited information you gave.     We don't know how the engines are being run.

   The time between oil changes.

   The type of oil being used.

   The quality of the gas and at least a dozen more    items.

   



   Since you identified that the engines have low compression - Have you    identified where they are leaking from?  

   Valves or Rings?

   Any gasket leaks?

   



   Fill in the blanks on the above questions and I'll try    to diagnose.

   



   GOOD LUCK,

   Barry

   



   



	


 

  

  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Fri Oct 22, 2010 7:48 am Post subject: low compression on Jabiru engine using AVGAS

Good Morning Doug,

  

 Your comment is correct as far as it goes. 

  

 However, you will note that Jabiru does suggest changing the jets and the  metering rod to get the mixtures desired. The Bing Carburetor does automatically  adjust the mixture due to changes in altitude, but the changes at high power and  at cruise are made by changing the components in the carburetor to compensate  for different RPM on various engine applications. 

  

 Christian's problem still may be heavily associated with the 100/130 fuel  that is being used. 100/130 is NOT the same as 100LL. If the 100/130  AVGAS still has the composition that we in the USA had before 100LL came on  the scene, he is getting an abominable amount of lead in the engine. If it is  running rich at relatively low power settings (below seventy-five percent or so)  lead will be built up on valve stems, spark plugs, and in the ring lands. No  more lead should be used than is absolutely required for the compression being  used. 

  

 Higher octane fuel does no good at all in an engine that does not have a  compression ratio requiring it. Getting a high octane rating by using lots of  lead is especially hard on the engine. The more modern USA standard 100 LL has a  LOT less lead than does/did 100/130 AVGAS.

  

 Not sure which is available where Christian operates, but lead is bad and  should be avoided wherever possible.

  

 While the fuel used at full takeoff power must be rich enough to have a  suitable octane rating to avoid detonation at that power, no lead at all is  needed at cruise power and operating on the lean side of best power for cruise  is always the best for the engine provided that distribution is adequate.

  

 Jabiru attempts to get a suitably rich mixture at takeoff power and a  suitably lean mixture at cruise power by selecting appropriate fuel rods and  suitable jetting. The Bing Carburetor works great when it is suitably set up.  Personally, I would prefer to have manual mixture control, but I am horribly old  fashioned. <G>

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 10/22/2010 10:09:01 A.M. Central Daylight Time,  Kayberg(at)aol.com writes:

  	  Quote: 	
		        Barry,

    

   Do you have significant experience with Jabiru engines?   Your    comments would indicate a  background in other engines (Ly-Con) which are    not  the same as a Jabiru.

    

   For example, the carbs are not leanable, nor is leaning suggested by    Jabiru

    

   Further, since the Jab engines have such a low oil volume, your Marvel    Mystery Oil suggestion is not a good one, and  might generate a whole    other set of problems.

    

   Doug Koenigsberg

    

    

    

   In a message dated 10/20/2010 11:10:11 P.M. Eastern Daylight Time,    flyadive(at)gmail.com writes:

    	  Quote: 	
		  Christian:      



     There is a VERY good chance you are experiencing the same      problems MANY engines here in the USA are experiencing while running on      100LL.  100LL is really not Low Lead at all.  It is four      times the lead as the old AvGas 80.

     Since you are having low compression I would bet that they      are experiencing lead/coke build up in the valve stems.

     If the build up goes untreated the valve will stick in the down      (open) position and if the valve - cylinder clearance is      an interference fit they will be spitting out valve parts.       AND even if it is not an interference fit, the compression      will go to zero and still again they will be looking for an emergency field      and new engine parts.

     



     The options are:

     Use TCP in the fuel to reduce lead build up

     LEAN AGGRESSIVELY - ALL THE TIMES -- Even when taxing.

     Use AUTO - MoGas or a mixture of MoGas & AvGas.  Just keep the      octane where needed.

     1 hour flight before every oil change put in one quart of MMO (Marvell      Mystery Oil) - This helps clean the build up.

     



     Now, these suggestion come with the limited information you gave.       We don't know how the engines are being run.

     The time between oil changes.

     The type of oil being used.

     The quality of the gas and at least a dozen more      items.

     



     Since you identified that the engines have low compression - Have you      identified where they are leaking from?  

     Valves or Rings?

     Any gasket leaks?

     



     Fill in the blanks on the above questions and I'll try      to diagnose.

     



     GOOD LUCK,

     Barry

     



     



	


   

    

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  [quote][b]

info(at)jabiru.cl
Guest

Posted: Mon Oct 25, 2010 6:12 pm Post subject: low compression on Jabiru engine using AVGAS

Thank you guys for the info and commends. I think the same way that the AVGAS here could be a problem. I’m still investigating the problem and if I find something interesting for you, I will post it in this forum again.  

   

Thank you,  

   

Christian   

         

  

De: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] En nombre de BobsV35B(at)aol.com

 Enviado el: Friday, October 22, 2010 12:45 PM

 Para: jabiruengine-list(at)matronics.com

 Asunto: Re: low compression on Jabiru engine using AVGAS  

  

     

Good Morning Doug,  

    

   

    

Your comment is correct as far as it goes.   

    

   

    

However, you will note that Jabiru does suggest changing the jets and the metering rod to get the mixtures desired. The Bing Carburetor does automatically adjust the mixture due to changes in altitude, but the changes at high power and at cruise are made by changing the components in the carburetor to compensate for different RPM on various engine applications.   

    

   

    

Christian's problem still may be heavily associated with the 100/130 fuel that is being used. 100/130 is NOT the same as 100LL. If the 100/130 AVGAS still has the composition that we in the USA had before 100LL came on the scene, he is getting an abominable amount of lead in the engine. If it is running rich at relatively low power settings (below seventy-five percent or so) lead will be built up on valve stems, spark plugs, and in the ring lands. No more lead should be used than is absolutely required for the compression being used.   

    

   

    

Higher octane fuel does no good at all in an engine that does not have a compression ratio requiring it. Getting a high octane rating by using lots of lead is especially hard on the engine. The more modern USA standard 100 LL has a LOT less lead than does/did 100/130 AVGAS.  

    

   

    

Not sure which is available where Christian operates, but lead is bad and should be avoided wherever possible.  

    

   

    

While the fuel used at full takeoff power must be rich enough to have a suitable octane rating to avoid detonation at that power, no lead at all is needed at cruise power and operating on the lean side of best power for cruise is always the best for the engine provided that distribution is adequate.  

    

   

    

Jabiru attempts to get a suitably rich mixture at takeoff power and a suitably lean mixture at cruise power by selecting appropriate fuel rods and suitable jetting. The Bing Carburetor works great when it is suitably set up. Personally, I would prefer to have manual mixture control, but I am horribly old fashioned. <G>  

    

   

    

Happy Skies,  

    

   

    

Old Bob  

    

   

      

In a message dated 10/22/2010 10:09:01 A.M. Central Daylight Time, Kayberg(at)aol.com writes:  

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Barry,  

    

   

    

Do you have significant experience with Jabiru engines?   Your comments would indicate a  background in other engines (Ly-Con) which are not  the same as a Jabiru.  

    

   

    

For example, the carbs are not leanable, nor is leaning suggested by Jabiru  

    

   

    

Further, since the Jab engines have such a low oil volume, your Marvel Mystery Oil suggestion is not a good one, and  might generate a whole other set of problems.  

    

   

    

Doug Koenigsberg  

    

   

    

   

    

   

    

In a message dated 10/20/2010 11:10:11 P.M. Eastern Daylight Time, flyadive(at)gmail.com writes:  

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Christian:     

   

    

There is a VERY good chance you are experiencing the same problems MANY engines here in the USA are experiencing while running on 100LL.  100LL is really not Low Lead at all.  It is four times the lead as the old AvGas 80.  

    

Since you are having low compression I would bet that they are experiencing lead/coke build up in the valve stems.  

    

If the build up goes untreated the valve will stick in the down (open) position and if the valve - cylinder clearance is an interference fit they will be spitting out valve parts.  AND even if it is not an interference fit, the compression will go to zero and still again they will be looking for an emergency field and new engine parts.  

    

   

    

The options are:  

    

Use TCP in the fuel to reduce lead build up  

    

LEAN AGGRESSIVELY - ALL THE TIMES -- Even when taxing.  

    

Use AUTO - MoGas or a mixture of MoGas & AvGas.  Just keep the octane where needed.  

    

1 hour flight before every oil change put in one quart of MMO (Marvell Mystery Oil) - This helps clean the build up.  

    

   

    

Now, these suggestion come with the limited information you gave.  We don't know how the engines are being run.  

    

The time between oil changes.  

    

The type of oil being used.  

    

The quality of the gas and at least a dozen more items.  

    

   

    

Since you identified that the engines have low compression - Have you identified where they are leaking from?    

    

Valves or Rings?  

    

Any gasket leaks?  

    

   

    

Fill in the blanks on the above questions and I'll try to diagnose.  

    

   

    

GOOD LUCK,  

    

Barry  

    

   

    

   

  	
  

    

   

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