tonyplane(at)bellsouth.ne
Guest
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 Posted: Thu Dec 07, 2006 8:04 am Post subject: JabiruEngine cooling |
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Rick,
| Quote: | From my archives,
see below.
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Tony Graziano
Zodiac 601XL/Jab3300A SN33A644, N493TG 179 hrs
Submitted By:
charles.long(at)gm.com
Email List:
Zenith-List
Name:
Charles F. Long
Date:
Oct 23 2005
Subject:
Cooling improvements on the Zenith 601HDS w/Jabiru 3300
Description:
During my first few hours of flight, I experienced elevated cylinder
head temperatures on my Zenith 601HDS with Jabiru 3300A engine. Also had
issues with Exhaust Gas Temperature imbalance at full throttle. The
following is a summary of changes made to improve the situation. This really
just builds on the recommendations of Jabiru and Zenith to provide plenty of
cooling for the 6 cylinder engine. I would like to thank Jeff Small, Fred
Hulen, Stan Challgren as well as Pete Krotje at US Jabiru and Andy Sylvester
at Sun Coast for their contributions. As a place to start, US Jabiru
provides some good cooling suggestions at their website:
My aircraft has the following modifications:
1) Fuel Economy Carb Kit as supplied by Jabiru.
2) Gull wing baffles between cylinders as recommended by Jabiru
3) Full deflectors angled down between the spark plugs of cylinder #5
& #6 as recommended by Jabiru.
4) Smaller deflectors angled down between the spark plugs of #3 & #4.
These middle cylinder deflectors usually need some tuning. Would suggest
starting with 3/4" tall. On #3, I stayed at 3/4", on #4 ended up trimming
down to 1/2".
5) The inlet to the ram air ducts has a gap between the duct and the
cylinders at the bottom. This allows air to escape downward without doing
any useful work. I added some .025" aluminum plates that butt up against
cylinder's #1 & #2 to prevent this from happening. To reduce the over
cooling of the front two cylinders and force more air upward to the rear
cylinders, I angled the material upward about an 2-3กจ. The exact height
needs to be determined by trial end error. The new XL cowl has openings that
are quite small and located high on the cylinders. My modification attempts
to duplicate the XL cowl openings and seems to work quite well. At the
onset, this change appears to be counter-intuitive. Just keep it mind, the
goal is to get as much use out of every air molecule as possible!
6) Small baffles mounted between valve tappet covers. This prevents
more air from escaping without doing any useful work.
7) There is a temptation to add an L angle to the bottom rear of each
ram duct. I tried this change and it elevated my temps rather than reducing
them.
 The oil cooler inlet is keep quite small to allow more air to find
it's way through the cylinders. I ended up with about a 1.75" x 4.00"
opening. The Jabiru website provides a good discussion on this. I tried a
much bigger opening as can be seen in the picture and it provided very
little benefit.
9) Don't forget to keep your oil level midway between the Full and Add
mark. Jabiru indicates that overfilling can cause high oil temps.
My #1 cylinder was running much cooler than the #2 cylinder with
identical intake openings. I rotated the bottom of the carb 5-10 degrees
towards #1 and that took care of it. The main jet feeds the carb at the
bottom so if the carb is tilted, it can direct more fuel towards one bank of
cylinders than the other.
At full throttle, EGT's from left to right bank were 150 F different.
I suspected that air entering the carb through the 90 degree intake elbow
was piling up on the outside of the curve. I installed a vertical divider in
the elbow to keep left side air separated from the right side air. This
worked beautifully. My EGT's are now balanced within roughly 50 F at all
throttle settings including WOT. The divider was fabricated out of a piece
of 6061T6 aluminum - 5.25" x 3" x .016". The upper and lower edges were
rolled around a 1/16" cable to add stiffness and prevent cutting of the
rubber elbow. Finished height is just slightly over 2.25 inches so it fits
snuggly within the elbow. After rolling the edges, the part was bent 90
degrees to fit the elbow contour by wrapping around a 2" diameter plastic
pipe. After it springs back, you end up with a 2" bend radius whichis
equivalent to the center radius of the elbow. Once the part is finished, the
cable can be removed (prevents a potential corrosion issue). The rubber
elbow is quite pliable in the free state, so the flow divider installs quite
easily. After installation, the divider is trapped pretty well in all
directions.
With the Aid of my Engine Information System from Grand Rapids
Technology, I was able to monitor my progress for each Cylinder Head
Temperature: I now have the following readings at 60 F ambient temperature
(my engine has 28 hours TT, so temps have fallen after break-in):
--------------------------------------------------------------------
RPM IAS CHT1 CHT2 CHT3 CHT4 CHT5 CHT6 EGT5 EGT6
--------------------------------------------------------------------
2600 110 247 228 259 247 272 245 1465 1423
2700 120 242 221 253 239 265 240 1486 1451
2800 125 242 226 252 242 265 244 1512 1498
2900 130 253 246 260 260 268 262 1482 1538
WOT 138 288 293 293 298 301 297 1463 1482
--------------------------------------------------------------------
This was a quickie test and temps/speeds were not totally stabilized.
Oil temps varied from 200-230F depending on Throttle setting. This is an
area where a NACA inlet could improve Oil Cooler efficiency. The new XL cowl
incorporates one of these. The Flight Test was run at 3500 ft MSL and an
ambient of 60F. Wheel pants and gear fairings are installed with an
otherwise stock airframe.
The Jabiru is running very nice. I'm happy with the installation,
power and smoothness after getting through these initial teething problems.
Fuel burn at lower cruise settings is estimated at a miserly 4 gph. With the
fat wing, I suspect fuel burn will go way up at the higher cruise speeds.
Chuck Long
Zodiac 601HDS
N601LE, 28 hr TT
=Big5BQmV0d2VlbiBDeWxpbmRlci5qcGc==.jpg
Photo 1
=Big5BT2lsIENvb2xlciBPcGVuaW5nLkpQRw===.jpg
Photo 2
=Big5BUmFtIER1Y3QgRGVmbGVjdG9yLmpwZw===.jpg
Photo 3
=Big5BUmlnaHQgUmFtIER1Y3QuSlBH=.jpg
Photo 4
=Big5BVmVydGljYWwgRmxvdyBEaXZpZGVyLkpQRw===.jpg
Photo 5
---------------
[quote] Time: 06:47:53 AM PST US
From: "rick tedford" <rick.tedford(at)sympatico.ca>
Subject: Re: RE: JabiruEngine-List Digest: 0 Msgs -
12/02/06
Hello ET : I had similar problems , but , when I purchased the cowl from
JabUSA my cht,s went down substantially . I now run at about 250F.on #6
and
with very little variation on the others .
My original cowl came from Aus.and I was not happy with same .
Hope this helps
Rick
DO NOT ARCHIVE
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