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tkben002

Joined: 06 Jul 2011
Posts: 54
Location: Alexandria, LA

Posted: Sun Sep 18, 2011 1:45 pm Post subject: Thom, Chris or Jabiru owners

I am at a point where I do not know what to do next.  I have a Kolbra with a solid lifter Jabiru 2200 with 50 hrs on the engine and 25 on the plane.

I have been battling a high cht temp on cylinders 3 and 4.  I only have 2 cht probes and they are currently on #3 and 4 which are my hottest (#4) and coldest (#3).  The coldest will hit around 260F in climb and cool off to about 200f in cruise.  The hottest will hit 345 to 350f in climb then I generally lower the nose and cool it off alittle and at cruise will range from 315 to 330f.  I can adjust these temps somewhat by tilting the carb back and forth and when the carb is close to center but not quite I can get even cht's on both cylinders in idle and up to about 1300 rpm while taxiing.



Now, the harder part.  My egt's have been about 100f apart and pretty consistent around 1100 on cylinders 2 and 4 and 1200 on cylinders 1 and 3.  Last weekend a friend at the airport (with a sonex and 3300) noticed that I did not have a tube from the carb to the air filter and recommended that I put one in so, I did.  Yesterday when I flew all was as usual except when I reached 100ft altitute my red light on the eis was going off and I was not expecting that.  The EGT on cylinders 1 and 3 was up to 1450-1460 in full power climb and the egt on cylinders 2 and 4 what around 1380.  As I began to throttle back and egts reduced when at pattern altitude and around 2700 rpm.  The egt on cylinders 1 and 3 took longer and a little lower rpm to cool off back in the 1368 or less range.  



Next I commense to tilting the carb to adjust the fuel/air mixture to cylinders 1 and 3 to get the egts down and nothing I do makes any difference.  It was recommended to reject the carb and I was handed a 283 jet and replaced the 276 that was in the carb.  The main jet is a 255.  I flew some more and the egts on cylinders 2 and 4 reduced to around 1225 to 1250 but the egts on cylinders 1 and 3 was still at 1450 in full power climb.  I suspected a fuel flow issue so I tried the electric fuel pump and it made no difference either.  



I did not want to do any damage so I took off the air vent hose on the carb and went around the pattern and all was back to usual except when I reduced throttle in the pattern the engine started sputtering and I thought it was going to quit but It didnt.  Needless to say but I think it was too rich so I jetted the carb back to the 276 that came with it and it went back to usual.  Now I am back to square one.  I know the mixture is rich and I am burning more than 4 gallons per hour and do not know what to do next.



Thom and Chris, I know each of you have the jabiru 2200 on yours, any recommendations?  I was told that since my BRS sits right in front of my carb that it could be causing some problems and that I should run a remote air filter with scat hose.



Thanks,

Travis Bennett

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sun Sep 18, 2011 4:23 pm Post subject: Re: Thom, Chris or Jabiru owners

Hello Travis,



   First of all....I have no idea what jet I have in my carb...and I only have cht and egt for 2 cylinders which to start with were on cyls 3 & 4 ( the ones toward the leading edge of the wing)..before I changed the cht to 1&2, cht's on 3 & 4 would run 260 - 280* ..but since I over headed my #2 cyl in a ground test run last winter I moved the cht's to 1 & 2 so I know what the back cylinders are doing...when you look at the picture I submitted, remember that the egt's are for the front cylinders and I suspect #4 is lower because the compression was lower in that cylinder and this winter I may clean up and re-ring that cylinder...how ever , since it doesn't  burn a drop of oil now after redoing the #2 cylinder and at that rpm it seems to burn 3 gph,I may not do anything with it. I wish I had probs on all the cylinders...



Tilting the carb WILL make a difference...after I got her together  this summer I had the carb on straight and level and on climb at WOT my egt's went to 1390 and when throttled back went back down....after tilting the carb a couple of times I never had a problem.



my cht 's even on 95* days stay at 320* and coming home the other evening the OAT was around 65-70 *.



I'm not sure what to tell you,but hope this gives you something to shoot for...according to Jim at Jabiru Pacific I'm right in the ball park .



chris ambrose

M3X/Jabiru A-2200  225. hrs

N327CS

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ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sun Sep 18, 2011 4:30 pm Post subject: Re: Thom, Chris or Jabiru owners

Travis,



What rpm are you running at 4 gph??  And I was told you have to have that tube going into the carb to make it work right...



chris ambrose

M3X/jab a 2200

N327cs

tkben002

Joined: 06 Jul 2011
Posts: 54
Location: Alexandria, LA

Posted: Sun Sep 18, 2011 4:37 pm Post subject: Re: Thom, Chris or Jabiru owners

I am not sure what gph I am running but as I have not done the math because I have not kept good enough records for it, but I am sure it is over 4 gph right now.  Now when I ran for 1.2 hours yesterday with the tube hooked to the carb and airfilter the engine ran better and seemed to have more power but I was really focused in on the high egt.  I only have 2 egt and 2 cht probes and wish I had all 4.  I moved mine from #1 and 2 in the back to the front 2 and that is where they are now as they were the fartherest apart.



thanks,

Travis Bennett

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sun Sep 18, 2011 4:48 pm Post subject: Re: Thom, Chris or Jabiru owners

Travis...



I am confused.....your hottest cylinders are the ones at the front openings of the air scoops??  ( 3 & 4 ) ??



chris ambrose

tkben002

Joined: 06 Jul 2011
Posts: 54
Location: Alexandria, LA

Posted: Sun Sep 18, 2011 5:35 pm Post subject: Re: Thom, Chris or Jabiru owners

Actually, my hottest cylinders are #2 and 4 with #4 being the hottest.  My coldest is #3.  It seems weird that my hottest cylinder is the one in front (fartherest away from the prop).



Travis Bennett

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sun Sep 18, 2011 5:47 pm Post subject: Re: Thom, Chris or Jabiru owners

Travis...



That is strange......I don't get it.....lets see what Thom thinks...Hmmmm...



chris ambrose

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Sep 19, 2011 4:40 am Post subject: Re: Thom, Chris or Jabiru owners

Travis,



I just got back from the Jabiru Engine seminar at Great Barrington, Mass. last night and learned a good bit from this excellent class which was far better than the Rotax 912 class I went to about 6 years ago.



Both the CHTs and EGTs are important but must be addressed separately. Let start with the EGTs.

1) The float bowl vent nipple MUST be connected to the clean side of the air cleaner for the carb to have stable mixture.

2) The location of the Carb directly behind the BRS (just like on my Slingshot) is not an issue, so ignore what "someone said " in this regard.

3) My carb has the original Bing Jet Needle in it, not the newer Jabiru designed needle.

4) I tried changing the main jet to reduce EGTs at WOT climb. Mine was not as bad as yours but too high. This helped a little but not enough, even with two sizes bigger main jet.

5) I changed to smaller needle jet to increase cruise EGTs, again it helped some but not enough. Mine were not as bad as yours.

6) Pete Krotje told me at the seminar that the jet changes are not as effective with the old Bing needle as they are with the Jabiru needle so changing that will be my next step and I suggest that be yours too, if you have the Bing needle.



You can easily tell which needle you have by looking at it. The Bing needle has the straight (linear) taper. The Jabiru needle has a visually obvious step, no sharp edges but a rather quickly changing taper. You can see this without dismantling the carb. Remove the air filter, stick you finger in the inlet throat and raise the piston/slide to see the needle. If your carb already has the Jabiru needle and you change the jets and it doesn't work, your next step is to call for technical help from Shelbyville. 



Attached is an image from the Carb Tuning service bulletin JSB018-2 which shows which jets/needles are recommended base on your serial number and carb size and lifter type. Take these as a starting point and make small changes from there.

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_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Sep 19, 2011 4:45 am Post subject: Re: Thom, Chris or Jabiru owners

Travis,

I forgot to ask what prop you have on your Jabby and what rpms you are seeing during WOT climb at Vy and WOT in straight and level. These are an important part of EGT tuning.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

jbhart(at)onlyinternet.ne
Guest

Posted: Mon Sep 19, 2011 5:05 am Post subject: Thom, Chris or Jabiru owners

At 02:45 PM 9/18/11 -0700, you wrote:

 	  Quote: 	
		  

........................................
	


 	  Quote: 	
		  

Now, the harder part.  My egt's have been about 100f apart and pretty 

consistent around 1100 on cylinders 2 and 4 and 1200 on cylinders 1 and 3.  
	


Last weekend a friend at the airport (with a sonex and 3300) noticed that I 

did not have a tube from the carb to the air filter and recommended that I 

put one in so, I did.  Yesterday when I flew all was as usual except when I 

reached 100ft altitute my red light on the eis was going off and I was not 

expecting that.  The EGT on cylinders 1 and 3 was up to 1450-1460 in full 

power climb and the egt on cylinders 2 and 4 what around 1380.  As I began 

to throttle back and egts reduced when at pattern altitude and around 2700 

rpm.  The egt on cylinders 1 and 3 took longer and a little lower rpm to 

cool off back in the 1368 or less range.  

 	  Quote: 	
		  

.................................
	


Travis,



I am not a Jabiru engine owner, but I can explain part of what happened to 

you.



The reason you experienced higher EGT's is because you lowered the air 

pressure over the fuel in the float bowl.  This action will cause a leaner 

running engine.  In addition the pressure is controlled by the pressure drop 

of the air passing through the filter medium.  And, as you open the 

throttle, this pressure drop increases as the engine rpm goes up too.



I experimented with an air scoop on the Victor 1+ try and recover some of 

the air pressure lost while flowing through the filter.  Check out 

http://jackbhart.com/firefly/firefly147.html, especially the first data 

column.  At maximum rpm there was almost a six inch water pressure drop 

across the filter when the ram air pressure was applied.  Your result will 

be similar depending on the filter size relative engine displacement, and 

filter dirt load.



Jack B. Hart FF004

Winchester, IN

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Sep 19, 2011 5:06 am Post subject: Re: Thom, Chris or Jabiru owners

Travis,



CHTs are the other issue which in an uncowled pusher can be addressed only by modifying the baffles within the air ducts on top of the cylinder heads. 



At the inlet of the ducts there should be an aluminum baffle that blocks the bottom half of the cylinder head of #3 and #4. If you don't have one there, make and install one. If it covers more than the bottom half or less than the bottom half, modify it so that it stops at the middle of the cylinder head.



If you already have these baffles as specified, the next step is to add/modify the upper baffles (attached to the inside of the upper surface of the air ducts. These should be angled about 45 degrees to deflect incoming air downwards. Jabiru makes them by adding molding in fiberglass baffles but I don't see why aluminum riveted in place would not work as well. There should be one above the center of cylinder #3 and #4. After ensuring the inlet baffles are correct, you increase the CHT of the cold cylinder by shaving off the upper baffle above that cylinder about 1/8" at a time (to allow more air to pass above) before flight testing. To lower the CHT on the hot cylinder, you add to the upper baffle above that cylinder about 1/8" at a time (to direct more air down around the hot head) between flight tests.



Since you don't have CHT sensor on cylinders #1 and #2, you don't know what modifications to make. I suggest you fix the #3 and #4 then move the senors to #1 and #2 and repeat the process.



This can be time consuming and tedious but worth the effort. Once you get them right you won't have to fuss with them ever again, under normal circumstances. 



I was lucky. My CHTs are perfect because the builder of my Slingshot carefully went through this process. 



Back to EGTs:

Once I get my Jabiru needle installed I'll report back on the changes to my EGTs at during climb and cruise.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Mon Sep 19, 2011 8:10 am Post subject: Re: Thom, Chris or Jabiru owners

Thom...



Do you have any pictures of the scoops/baffles??



Thanks,

chris ambrose

M3X/Jab

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Sep 19, 2011 8:27 am Post subject: Re: Thom, Chris or Jabiru owners

Chris,



I should have taken some photos of the Jabiru J230 (3300) engine that was at the seminar, but did not. Sorry. The upper deflectors (better term than baffle, I think) attached to the upper surface inside the Jabby air ducts supplied with the engine are full width inside the duct but tend to be shorter(height) in the front and longer(deeper) in the back cylinders.  On the J230 I would guess that the front cylinder air deflector was probably less than 1" top-to bottom so that a good bit of air is allowed to pass on to the aft cylinders. The 2nd deflector (centered over the second row of cylinders was perhaps 1/2" longer. I did not measure these so these are pure guesses from my visual memory.



Each engine/airframe combination must have these deflectors  customized for optimum results. It is actually easier on our pushers because we don't have to mess with cowl inlet and outlet pressure ratios.  It is trial and error but definitely worth the effort, in my opinion. 



All of my CHTs normally are within 20F of each other in cruise but a bit more than that in WOT climb, which is pretty close. Mine normally read around 260F -280F during cruise with spark plug CHT rings (not some other technique used by others).

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Mon Sep 19, 2011 10:52 am Post subject: Re: Thom, Chris or Jabiru owners

Thom...



Am I headed in the right direction??



chriis ambrose

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Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Sep 19, 2011 11:29 am Post subject: Re: Thom, Chris or Jabiru owners

Chris,

It is difficult to tell from your photos but the last one looks like it is about right for the rearmost cylinder. The front cylinder air deflectors should be no more than half that height (maybe less?), as a starting point. 



Keep in mind that the goal is to have approximately equal amounts of air flow downwards around both cylinders on each side. Make your deflectors such that they look like they might do that and that should be a good first start. The one thing that I did notice is that the deflectors are mounted directly above the centerline of the cylinder at approximately 45 degrees from the straight back airflow (like full flaps on the wing) thus deflecting part of the air downwards.



What have your CHTs been running in cruise? How much difference between hottest and coolest? What about oil temp?

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Mon Sep 19, 2011 12:08 pm Post subject: Re: Thom, Chris or Jabiru owners

Thom..



front cylinders were running 260-270----and the rears low 300....oil temp since the cooler  is 160-170...I will start with the rears  and see what happens...are yours straight across or contoured to the fins??



chris

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Sep 19, 2011 12:21 pm Post subject: Re: Thom, Chris or Jabiru owners

Chris,

You have asked me an embarrassing question. Although I've had my air ducts off numerous times, to do head bolt torque checks and valve clearance adjustments, I've never examined the deflectors. Since the CHTs have always been close to each other and all in normal range, I never bothered to look at them closely.   



My advise is based on what I learned in the Jabiru class I attended this past weekend. The rear most deflector on the 3300 powered J230 (factory built) I saw this weekend was contoured to the heads, like your rear one.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

tkben002

Joined: 06 Jul 2011
Posts: 54
Location: Alexandria, LA

Posted: Mon Sep 19, 2011 2:24 pm Post subject: Re: Thom, Chris or Jabiru owners

Thom,

The prop is a warp drive 58" ground adjust.  The most rpm I have gotten in a climb is 3k but mostly 2900 to 2950.  (when the tube was attached to the carb is when I saw the 3k).  I do not have any baffles in my air scoops at all (picture attached).  Can you give more info on the front baffles and rear baffles, I think I understand how to make the top baffles pointing down on the plugs.  If making a fence on the front of the front 2 cylinders how do you attach it to the cylinders ( just screw into/between the fins with the right size screw?)



I checked my needle in the carb and it is straight as an arrow, no taper that I could see.  Is that hard to change?



Travis Bennett

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Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Sep 19, 2011 3:00 pm Post subject: Re: Thom, Chris or Jabiru owners

Travis,

The first thing I notice looking at the photo you posted is that the spark plug wires should NOT be routed through the opening of the air ducts. They are blocking a lot of air flow. Mine are routed over the top. See attached photo.



The jet needle can be changed easily by removing the top(27 in drawing) of the carb (4 screws - 28 in drawing) and pulling the diaphragm/slide out. Once the slide(19)/diaphragm is on your bench take the largest common screw driver that will fit down in the center hole of the slide and remove the aluminum plug from the slide. This threaded plug (22 in drawing) holds in the jet needle. The needle is held in the slide with a tiny circlip(21 in drawing). In the Bing needle there are 4 annular grooves that the circlip can be located in. Normal position is third from the top (2nd from the bottom).  Replace this with the latest Jabiru needle for the 4 cylinder engines. The Jabiru needle has only one annular groove for the circlip. All this assumes that some idiot did not put too much torque on the aluminum plug when screwing it in OR applied permanent loctite on the threads so you can't get it out. MINE was like that so I got another slide/diaphragm from a surplus Bing 94 carb which I can remove the aluminum threaded plug from. I do not use loctite when replacing this plug because it is aluminum and therefore has a high coefficient of friction and will not back out by itself. Don't overtorque it or you won't get it out again. 



When you've replaced the Bing jet needle with the Jabiru jet needle (call Jabiru USA for this part) in the slide and the aluminum threaded plug, it is time to replace the slide/diaprhagm into the carb top. The bottom of the diaphragm has a protrusion on one side and one side of the carb body has a matching depression in which the diaphragm protrusion fits into. These must be aligned carefully when re-fitting the carb top.



Hope this helps.

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_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

tkben002

Joined: 06 Jul 2011
Posts: 54
Location: Alexandria, LA

Posted: Mon Sep 19, 2011 3:26 pm Post subject: Re: Thom, Chris or Jabiru owners

Thom,

Do you have any pix of the front of your baffle installation?  Where is your BRS rocket mounted?



I kinda figured the spark plug wires should not be run thru the opening I just havent gotten around to moving them yet, but I will probably do that first.  Still thinking I should probably just call Jabiru and buy some new ramair ducts as mine seem a little on the small side.



Travis Bennett

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