Today's Message Index:
----------------------
1. 04:54 AM - Re: Coils (TELEDYNMCS@aol.com)
2. 05:54 AM - Re: Coils (Andy Silvester)
3. 07:02 AM - Cylinder cooling issues - Guidance from Jabiru (Andy Silvester)
4. 11:10 AM - Re: Re: Coils (japhillipsga@aol.com)
5. 12:58 PM - RE : Cylinder cooling issues - Guidance from Jabiru (=?iso-8859-1?Q?J=E9rme_Delamare?=)
6. 01:40 PM - Re: RE : Cylinder cooling issues - Guidance from Jabiru (Andy Silvester)
7. 01:56 PM - Re: Re: RE : Cylinder cooling issues - Guidance from Jabiru ()
8. 02:04 PM - Re: Cylinder cooling issues - Guidance from Jabiru (Gilles Thesee)
9. 02:28 PM - Re: Cylinder cooling issues - Guidance from Jabiru (Peter Harris)
10. 02:38 PM - Re: Cylinder cooling issues - Guidance from Jabiru (Peter Harris)
11. 02:53 PM - Re: Re: Coils (Mervin Friesen)
12. 09:25 PM - Re: Re: Coils (Jim Crowder)
13. 09:45 PM - Re: RE : Cylinder cooling issues - Guidance from Jabiru (Jim Crowder)
14. 10:05 PM - Re: Re: RE : Cylinder cooling issues - Guidance from Jabiru (Jim Crowder)
15. 10:27 PM - Re: Cylinder cooling issues - Guidance from Jabiru (Gilles Thesee)
Message 1
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In a message dated 9/11/2007 2:58:42 AM Eastern Daylight Time,
jabiruengine-list@matronics.com writes:
Its very likely the coil, this problem had been occuring to earlier coils,
have
not heard much trouble since the 'leading GX' coils were replaced with the
'TEK'
ones some time ago. Also there should be fitted or retrofitted some heat
insulating
washers under the coils and air cooling tubes to cool the coils, details
in the installation instructions on dealers websites, or in the series of
articles called 'jaba chat' off the jabiru website. The 'transistorised'
parts
are inside the coil packs, just bolt in a replacement coil.
Greetings team,
FWIW, both the coils that came on my 3300 failed. My engine is 33A756,
purchased in January 05. One of the coils was dysfunctional at the first start
up,
and the other failed within about the first 20 hours or so. Both were way
out of spec when measuring the secondary side with an ohm meter. Clearly, they
were bad and it wasn't a gap issue. Both came from the factory installed with
the phenolic washers installed behind them.
I replaced both of the failed coils at my expense, at roughly $160 each, and
returned the failed coils to the dealer for warranty replacement. That was
well over a year ago and although I've mentioned it several times to the
dealer, Jabiru hasn't made good on either of the coils. In fact, they've made
no
effort to respond whatsoever. I also had a bad oil pressure sender which
failied at about 30 hours, and that, too, was replaced at my expense. I also
returned the OP sender to Jabiru for warranty replacement, but haven't heard a
peep out of them. I had expected more from Jabiru, but they seem to be following
the "Rotaxian" model of customer service.
Interestingly, the replacement coils, although appearing to be manufactured
by the same vendor, were considerably different from the ones that came on the
engine. The new coils, obtained from two different Jab dealers, were larger
and had a different orientation of the coil wire where it exits the body of
the coil. I took pictures of the differences between the old and new coils and
showed them to the dealer from whom I purchased my engine, but it didn't
seem to help my case one iota. IOW, I'm convinced that Jabiru knew they had a
problem with the original coils that came on the engine. Otherwise, they
wouldn't have changed to the larger size. The replacement coils have operated
flawlessly for about 80 hours now, but I still keep a spare on the shelf just
in
case.
Regards,
John Lawton
Whitwell, TN (TN89)
Europa N245E - Flying -107 hours
Message 2
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Hi John and Listers,
Here's the situation with coils and Jabiru: warranty replacements were available
for the 'Leading GX' types which were know to have a batch problem, some 3-4
years ago, and we as dealers made sure we replaced them as soon as the new ones
were available. Since then, Jabiru haven't recognized any subsequent failures
and refer to the following facts:
1. Engines are dyno-tested at the factory and leave in fully working order.
2. Coils break-down in over heating conditions so they recommend in their manuals
for additional air cooling to the coils from the ram-air ducts.
OK, that's the 'Jabiru' line. Of course as dealers we try to manage the interface
between the factory and customers, but if Jabiru refuse to honor a warranty
claim, the issue is with us to either resolve or not. In John's case, I did my
best to get the two coils changed under warranty, but Jabiru insisted it must
have been an installation issue. My mistake was not to keep John fully informed
of the situation and eventual decision, but it's often tricky to keep track
of these things when they drag-on for months while we wait for a factory response.
John, I will try to 'make-good' by offering you a $200 store - credit for parts,
but bear in mind this is a 'Suncoast' gesture and not from Jabiru
Andy Silvester
Suncoast Sportplanes, Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133890#133890
Message 3
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| Subject: | Cylinder cooling issues - Guidance from Jabiru |
The following information was received by Dealers from Jabiru, and is posted in
advance of being incorporated into manuals and warranty policy:
To avoid overheating problems of the Jabiru engines in non Jabiru installations,
it is vitally important that all installations provide a greater that 6 inch
of water, air pressure differential to provide enough cooling for the Jabiru
engine. Attached is a diagram of the tube placements to measure this and photos.
We are in the process of having this included in the engine manual as a condition
of warranty.
Attached is a diagram and photos that demonstrate how to perform this test.
Andy Silvester
Suncoast Sportplanes Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133901#133901
Attachments:
http://forums.matronics.com//files/kif_1152_medium_142.jpg
http://forums.matronics.com//files/kif_1151_medium_191.jpg
http://forums.matronics.com//files/kif_1150_medium_112.jpg
http://forums.matronics.com//files/kif_1149_medium_200.jpg
http://forums.matronics.com//files/kif_1148_medium_163.jpg
http://forums.matronics.com//files/9a016a0d_1_200.pdf
Message 4
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Andy, I knew you wee a standup guy when I first met you. Hurah for Andy and Suncoast!
A man and company worthy of our business. Best regards, Bill of Georgia
-----Original Message-----
From: Andy Silvester <info@suncoastjabiru.com>
Sent: Tue, 11 Sep 2007 8:53 am
Subject: JabiruEngine-List: Re: Coils
Hi John and Listers,
Here's the situation with coils and Jabiru: warranty replacements were available
for the 'Leading GX' types which were know to have a batch problem, some 3-4
years ago, and we as dealers made sure we replaced them as soon as the new ones
were available. Since then, Jabiru haven't recognized any subsequent failures
and refer to the following facts:
1. Engines are dyno-tested at the factory and leave in fully working order.
2. Coils break-down in over heating conditions so they recommend in their
manuals for additional air cooling to the coils from the ram-air ducts.
OK, that's the 'Jabiru' line. Of course as dealers we try to manage the
interface between the factory and customers, but if Jabiru refuse to honor a
warranty claim, the issue is with us to either resolve or not. In John's case,
I
did my best to get the two coils changed under warranty, but Jabiru insisted it
must have been an installation issue. My mistake was not to keep John fully
informed of the situation and eventual decision, but it's often tricky to keep
track of these things when they drag-on for months while we wait for a factory
response.
John, I will try to 'make-good' by offering you a $200 store - credit for parts,
but bear in mind this is a 'Suncoast' gesture and not from Jabiru
Andy Silvester
Suncoast Sportplanes, Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133890#133890
________________________________________________________________________
Email and AIM finally together. You've gotta check out free AOL Mail! - http://mail.aol.com
Message 5
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| Subject: | Cylinder cooling issues - Guidance from Jabiru |
Greater than 6 inch of water ! Sure ?
In my manual :" The required pressure drop across the cylinders at 1.3
Vs in
take off configuration is 4.3 cm (1.7") water gauge, minimum."
To obtain a dynamic pressure of 6 inch of water you need an Indicated
Air
Speed of 180 km/h (100 kts).
J=E9rme
-----Message d'origine-----
De : owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] De la part de Andy
Silvester
Envoy=E9 : mardi 11 septembre 2007 16:02
=C0 : jabiruengine-list@matronics.com
Objet : JabiruEngine-List: Cylinder cooling issues - Guidance from
Jabiru
<info@suncoastjabiru.com>
The following information was received by Dealers from Jabiru, and is
posted
in advance of being incorporated into manuals and warranty policy:
To avoid overheating problems of the Jabiru engines in non Jabiru
installations, it is vitally important that all installations provide a
greater that 6 inch of water, air pressure differential to provide
enough
cooling for the Jabiru engine. Attached is a diagram of the tube
placements
to measure this and photos. We are in the process of having this
included in
the engine manual as a condition of warranty.
Attached is a diagram and photos that demonstrate how to perform this
test.
Andy Silvester
Suncoast Sportplanes Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133901#133901
Attachments:
http://forums.matronics.com//files/kif_1152_medium_142.jpg
http://forums.matronics.com//files/kif_1151_medium_191.jpg
http://forums.matronics.com//files/kif_1150_medium_112.jpg
http://forums.matronics.com//files/kif_1149_medium_200.jpg
http://forums.matronics.com//files/kif_1148_medium_163.jpg
http://forums.matronics.com//files/9a016a0d_1_200.pdf
Message 6
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| Subject: | Re: RE : Cylinder cooling issues - Guidance from Jabiru |
Jerome,
Three things to point out:
1. The latest test has different reference points than before, when the pressure
was compared with ambient and at an airspeed of only 1.3 Vs.
2. The higher pressure differential reflects both pressure and suction, i.e. inside
the cooling duct is compared to a point adjacent to the cowling outlet.
3. The 6" differential will be obtained at normal cruise speeds, which is easier
to monitor in the air rather than (in my view) trying to maintain a speed of
1.3Vs and looking at the manometer.
I hope this clears-up the confusion. My advice is to use the later information
rather than that published in existing manuals - they will be updated soon.
Andy Silvester
Suncoast Sportplanes Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133956#133956
Message 7
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| Subject: | Re: RE : Cylinder cooling issues - Guidance from |
Jabiru
Someone previously posted what that 6" of water differential pressure would produce
as the reading on an ASI. Wasn't it something in the neighborhood of 60 mph?
Ed
---- Andy Silvester <info@suncoastjabiru.com> wrote:
>
> Jerome,
>
> Three things to point out:
>
> 1. The latest test has different reference points than before, when the pressure
was compared with ambient and at an airspeed of only 1.3 Vs.
> 2. The higher pressure differential reflects both pressure and suction, i.e.
inside the cooling duct is compared to a point adjacent to the cowling outlet.
> 3. The 6" differential will be obtained at normal cruise speeds, which is easier
to monitor in the air rather than (in my view) trying to maintain a speed
of 1.3Vs and looking at the manometer.
>
> I hope this clears-up the confusion. My advice is to use the later information
rather than that published in existing manuals - they will be updated soon.
>
> Andy Silvester
> Suncoast Sportplanes Inc.
Message 8
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| Subject: | Re: Cylinder cooling issues - Guidance from Jabiru |
Andy Silvester a crit :
> 1. The latest test has different reference points than before, when the pressure
was compared with ambient and at an airspeed of only 1.3 Vs.
> 2. The higher pressure differential reflects both pressure and suction, i.e.
inside the cooling duct is compared to a point adjacent to the cowling outlet.
> 3. The 6" differential will be obtained at normal cruise speeds, which is easier
to monitor in the air rather than (in my view) trying to maintain a speed
of 1.3Vs and looking at the manometer.
>
Andy, Jerome and all,
Thanks for this interesting data from Jabiru, and rather consistent with
other sources.
On a different type of engine, I'm achieving 140-150 mm H20 (5.5"- 6")
mean cylinder differential pressure (between upper and lower cowling) on
a 125-135 kt airplane.
Didn't retrieve direct Lycoming numbers, but a quick search yielded :
> Lycoming Engine Installation Manual does specify that the O-320 engine
> requires 5 - 1/2 inches of water while the O-360 engine should have 6
> - 1/2 inches pressure drop for good cooling.
(quoting from http://www.rv7-a.com/phase_1_page2.htm)
Of course, actual numbers will depend on the pressure measuring setup,
but those values are in the same ballpark.
FWIW,
Best regards,
--
Gilles
http://contrails.free.fr
Message 9
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| Subject: | Cylinder cooling issues - Guidance from Jabiru |
Andy,
Is this a requirement for cooling of the engine or for cooling the coils?
I think it would be very difficult to find a pressure differential of 6"
water at anything less than 140KTS. Can you confirm how this can be done. I
have taken measurements using a water manometer and found 4" static pressure
from a point near the cowl inlet at 120KTS.
Peter
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Andy
Silvester
Sent: Wednesday, 12 September 2007 12:02 AM
Subject: JabiruEngine-List: Cylinder cooling issues - Guidance from Jabiru
<info@suncoastjabiru.com>
The following information was received by Dealers from Jabiru, and is posted
in advance of being incorporated into manuals and warranty policy:
To avoid overheating problems of the Jabiru engines in non Jabiru
installations, it is vitally important that all installations provide a
greater that 6 inch of water, air pressure differential to provide enough
cooling for the Jabiru engine. Attached is a diagram of the tube placements
to measure this and photos. We are in the process of having this included in
the engine manual as a condition of warranty.
Attached is a diagram and photos that demonstrate how to perform this test.
Andy Silvester
Suncoast Sportplanes Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133901#133901
Attachments:
http://forums.matronics.com//files/kif_1152_medium_142.jpg
http://forums.matronics.com//files/kif_1151_medium_191.jpg
http://forums.matronics.com//files/kif_1150_medium_112.jpg
http://forums.matronics.com//files/kif_1149_medium_200.jpg
http://forums.matronics.com//files/kif_1148_medium_163.jpg
http://forums.matronics.com//files/9a016a0d_1_200.pdf
Message 10
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| Subject: | Cylinder cooling issues - Guidance from Jabiru |
Andy,
Now that I understand we are talking about differential pressure inlet vs
outlet pls disregard my last post.
But is it not sufficient to run within the required CHT ?
Peter
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Peter
Harris
Sent: Wednesday, 12 September 2007 7:28 AM
Subject: RE: JabiruEngine-List: Cylinder cooling issues - Guidance from
Jabiru
<peterjfharris@bigpond.com>
Andy,
Is this a requirement for cooling of the engine or for cooling the coils?
I think it would be very difficult to find a pressure differential of 6"
water at anything less than 140KTS. Can you confirm how this can be done. I
have taken measurements using a water manometer and found 4" static pressure
from a point near the cowl inlet at 120KTS.
Peter
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Andy
Silvester
Sent: Wednesday, 12 September 2007 12:02 AM
Subject: JabiruEngine-List: Cylinder cooling issues - Guidance from Jabiru
<info@suncoastjabiru.com>
The following information was received by Dealers from Jabiru, and is posted
in advance of being incorporated into manuals and warranty policy:
To avoid overheating problems of the Jabiru engines in non Jabiru
installations, it is vitally important that all installations provide a
greater that 6 inch of water, air pressure differential to provide enough
cooling for the Jabiru engine. Attached is a diagram of the tube placements
to measure this and photos. We are in the process of having this included in
the engine manual as a condition of warranty.
Attached is a diagram and photos that demonstrate how to perform this test.
Andy Silvester
Suncoast Sportplanes Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133901#133901
Attachments:
http://forums.matronics.com//files/kif_1152_medium_142.jpg
http://forums.matronics.com//files/kif_1151_medium_191.jpg
http://forums.matronics.com//files/kif_1150_medium_112.jpg
http://forums.matronics.com//files/kif_1149_medium_200.jpg
http://forums.matronics.com//files/kif_1148_medium_163.jpg
http://forums.matronics.com//files/9a016a0d_1_200.pdf
Message 11
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I'm impressed! Thanks Andy for the care you give to Jabiru engine owners.
Mervin Friesen
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Andy
Silvester
Sent: September 11, 2007 7:53 AM
Subject: JabiruEngine-List: Re: Coils
Hi John and Listers,
John, I will try to 'make-good' by offering you a $200 store - credit for
parts, but bear in mind this is a 'Suncoast' gesture and not from Jabiru
Andy Silvester
Suncoast Sportplanes, Inc.
1:37 PM
Message 12
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"Jabiru haven't recognized any subsequent failures
and refer to the following facts:
1. Engines are dyno-tested at the factory and leave in fully working order.
2. Coils break-down in over heating conditions so they recommend in their
manuals for additional air cooling to the coils from the ram-air ducts."
And if they fail with the additional cooling? So much for honoring their
warranty! I'm not impressed.
Jim Crowder
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com]On Behalf Of
japhillipsga@aol.com
Sent: Tuesday, September 11, 2007 12:09 PM
To: jabiruengine-list@matronics.com
Subject: Re: JabiruEngine-List: Re: Coils
Andy, I knew you wee a standup guy when I first met you. Hurah for Andy
and Suncoast! A man and company worthy of our business. Best regards, Bill
of Georgia
-----Original Message-----
From: Andy Silvester <info@suncoastjabiru.com>
To: jabiruengine-list@matronics.com
Sent: Tue, 11 Sep 2007 8:53 am
Subject: JabiruEngine-List: Re: Coils
<info@suncoastjabiru.com>
Hi John and Listers,
Here's the situation with coils and Jabiru: warranty replacements were
available
for the 'Leading GX' types which were know to have a batch problem, some 3-4
years ago, and we as dealers made sure we replaced them as soon as the new
ones
were available. Since then, Jabiru haven't recognized any subsequent
failures
and refer to the following facts:
1. Engines are dyno-tested at the factory and leave in fully working order.
2. Coils break-down in over heating conditions so they recommend in their
manuals for additional air cooling to the coils from the ram-air ducts.
OK, that's the 'Jabiru' line. Of course as dealers we try to manage the
interface between the factory and customers, but if Jabiru refuse to honor a
warranty claim, the issue is with us to either resolve or not. In John's
case, I
did my best to get the two coils changed under warranty, but Jabiru insisted
it
must have been an installation issue. My mistake was not to keep John fully
informed of the situation and eventual decision, but it's often tricky to
keep
track of these things when they drag-on for months while we wait for a
factory
response.
John, I will try to 'make-good' by offering you a $200 store - credit for
parts,
but bear in mind this is a 'Suncoast' gesture and not from Jabiru
Andy Silvester
Suncoast Sportplanes, Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133890#133890
----------------------------------------------------------------------------
--
Email and AIM finally together. You've gotta check out free AOL Mail!
Message 13
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| Subject: | Cylinder cooling issues - Guidance from Jabiru |
Andy Silvester
Suncoast Sportplanes Inc. writes:
"To avoid overheating problems of the Jabiru engines in non Jabiru
installations, it is vitally important that all installations provide a
greater that 6 inch of water, air pressure differential to provide enough
cooling for the Jabiru engine. Attached is a diagram of the tube placements
to measure this and photos. We are in the process of having this included in
the engine manual as a condition of warranty.
Attached is a diagram and photos that demonstrate how to perform this test."
On slow moving aircraft this may be very difficult to achieve. I will do my
best on my Kitfox 5, but for those of us who have already purchased our
engines and paid for them, this is an unfair position for Jabiru to take,
and a warranty amended after purchase is likely un-enforceable. The
warranty at the time of purchase is a part of our contract and cannot be
amended unilaterally. Let new buyers beware!! I want to be happy and will
do my best to achieve the 6 inch of water differential, but this does not
feel good.
Jim Crowder
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com]On Behalf Of Jrme
Delamare
Sent: Tuesday, September 11, 2007 1:58 PM
To: jabiruengine-list@matronics.com
Subject: RE : JabiruEngine-List: Cylinder cooling issues - Guidance from
Jabiru
Greater than 6 inch of water ! Sure ?
In my manual :" The required pressure drop across the cylinders at 1.3 Vs
in take off configuration is 4.3 cm (1.7") water gauge, minimum."
To obtain a dynamic pressure of 6 inch of water you need an Indicated Air
Speed of 180 km/h (100 kts).
Jrme
-----Message d'origine-----
De : owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] De la part de Andy
Silvester
Envoy : mardi 11 septembre 2007 16:02
: jabiruengine-list@matronics.com
Objet : JabiruEngine-List: Cylinder cooling issues - Guidance from Jabiru
<info@suncoastjabiru.com>
The following information was received by Dealers from Jabiru, and is
posted in advance of being incorporated into manuals and warranty policy:
To avoid overheating problems of the Jabiru engines in non Jabiru
installations, it is vitally important that all installations provide a
greater that 6 inch of water, air pressure differential to provide enough
cooling for the Jabiru engine. Attached is a diagram of the tube placements
to measure this and photos. We are in the process of having this included in
the engine manual as a condition of warranty.
Attached is a diagram and photos that demonstrate how to perform this
test.
Andy Silvester
Suncoast Sportplanes Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133901#133901
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Message 14
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| Subject: | Re: RE : Cylinder cooling issues - Guidance from |
Jabiru
Andy,
You say: "3. The 6" differential will be obtained at normal cruise speeds,
which is easier to monitor in the air rather than (in my view) trying to
maintain a speed of 1.3Vs and looking at the manometer."
It now sounds like I may have jumped the gun with my previous posting, but
Jabiru's idea of warranty is suspect as in the case of the coils. My
previous engine was water cooled which presented its own problems. I will
see how this all plays out. I do appreciate your getting out in front of
these issues. As I previously stated, I will do my best to be happy.
Jim Crowder
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com]On Behalf Of Andy
Silvester
Sent: Tuesday, September 11, 2007 2:40 PM
Subject: JabiruEngine-List: Re: RE : Cylinder cooling issues - Guidance
from Jabiru
<info@suncoastjabiru.com>
Jerome,
Three things to point out:
1. The latest test has different reference points than before, when the
pressure was compared with ambient and at an airspeed of only 1.3 Vs.
2. The higher pressure differential reflects both pressure and suction, i.e.
inside the cooling duct is compared to a point adjacent to the cowling
outlet.
3. The 6" differential will be obtained at normal cruise speeds, which is
easier to monitor in the air rather than (in my view) trying to maintain a
speed of 1.3Vs and looking at the manometer.
I hope this clears-up the confusion. My advice is to use the later
information rather than that published in existing manuals - they will be
updated soon.
Andy Silvester
Suncoast Sportplanes Inc.
--------
www.suncoastjabiru.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133956#133956
Message 15
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| Subject: | Re: Cylinder cooling issues - Guidance from Jabiru |
Peter Harris a crit :
> But is it not sufficient to run within the required CHT ?
>
Peter,
Of course it is.
Adequate cooling is certainly achievable with less than 5" in the case
of the Jabiru. I've seen adequately cooled Jabirus with less than
optimal intake diffusers and exits.
The mass flow through the fins is proportional to the square root of the
pressure differential. 4" would provide about 90 % of the flow at 5", so
things are not so critical.
By asking for optimal pressure drops, Jabiru is protecting itself
against warranty claims related to overheating.
Best regards,
--
Gilles
http://contrails.free.fr
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