Today's Message Index:
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1. 05:42 AM - Re: Thom, Chris or Jabiru owners (Thom Riddle)
2. 05:47 AM - Re: Thom, Chris or Jabiru owners (Thom Riddle)
3. 06:05 AM - Re: Thom, Chris or Jabiru owners (Jack B. Hart)
4. 06:09 AM - Re: Thom, Chris or Jabiru owners (Thom Riddle)
5. 09:14 AM - Re: Thom, Chris or Jabiru owners (ces308)
6. 09:31 AM - Re: Thom, Chris or Jabiru owners (Thom Riddle)
7. 11:55 AM - Re: Thom, Chris or Jabiru owners (ces308)
8. 12:33 PM - Re: Thom, Chris or Jabiru owners (Thom Riddle)
9. 01:11 PM - Re: Thom, Chris or Jabiru owners (ces308)
10. 01:24 PM - Re: Thom, Chris or Jabiru owners (Thom Riddle)
11. 03:26 PM - Re: Thom, Chris or Jabiru owners (tkben002)
12. 04:02 PM - Re: Thom, Chris or Jabiru owners (Thom Riddle)
13. 04:29 PM - Re: Thom, Chris or Jabiru owners (tkben002)
14. 04:48 PM - Re: Re: Thom, Chris or Jabiru owners (Thom Riddle)
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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.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352645#352645
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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)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352648#352648
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Subject: | Re: Thom, Chris or Jabiru owners |
At 02:45 PM 9/18/11 -0700, you wrote:
.........................................
>
>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.
>
..................................
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
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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)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352649#352649
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Subject: | Re: Thom, Chris or Jabiru owners |
Thom...
Do you have any pictures of the scoops/baffles??
Thanks,
chris ambrose
M3X/Jab
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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)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352669#352669
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Subject: | Re: Thom, Chris or Jabiru owners |
Thom...
Am I headed in the right direction??
chriis ambrose
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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)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352684#352684
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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
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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.
[Embarassed]
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)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352695#352695
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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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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.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=352717#352717
Attachments:
http://forums.matronics.com//files/bing_94_cut_away_440.jpg
http://forums.matronics.com//files/scaled_jabiru_rt_rear_144.jpg
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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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http://forums.matronics.com/viewtopic.php?p=352720#352720
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Subject: | Re: Thom, Chris or Jabiru owners |
Travis,,
My BRS is just like yours and located just like yours.
Thom
On Sep 19, 2011, at 7:31 PM, "tkben002" <tkben002@bellsouth.net> wrote:
>
> 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
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=352720#352720
>
>
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