Today's Message Index:
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1. 09:47 AM - Re: Re: EGTs and fuel quality (Andy Silvester)
2. 11:30 AM - Re: Re: EGTs and fuel quality (Lynn Matteson)
Message 1
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| Subject: | Re: EGTs and fuel quality |
Lynn,
Good work on the improvements! I'm sure many of us have found the same
situation of not knowing *exactly* what brings better performance,
especially when we are talking about a few % only, but those RPM increases
are significant. A note about SCEET ducting; I've used it with success on
the intake. Someone once told me that SCAT ducting has an equivalent
resistance of 23, meaning that 1 foot of SCAT ducting has the same
resistance to airflow as 23 feet of smooth-bore pipe! SCEET will be better,
but bear in mind one down-side which I'm sure won't affect you. The inner
'skin' of the duct can perish and suck flat if given enough time and bad
maintenance. It's a fair point, and a few A&Ps have told me it's a no-no to
use it on anything below ambient pressure, i.e. a carburettor intake. My
response (while being sympathetic to the argument) was that most
Experimental aircraft get better maintenance than certificated types(!) and
therefore the idea of a piece of duct not being internally inspected for
(say) 5 years or more is less likely in our world (.....or is it??!!)
Keep up the good work, Andy
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Lynn
Matteson
Sent: 19 April 2008 14:36
Subject: Re: JabiruEngine-List: Re: EGTs and fuel quality
Chuck-
I just flew my newly-modified and installed air duct (from airbox to
carb) and it works fine. I'd say great, but it didn't even out the
EGT's like I hoped, but it did *seem* to give me more WOT rpm. Of
course the weather has changed since I last checked for WOT rpm, but
before I'd have to point the nose down just a little to get 3000 rpm.
Today I could fly level and get 3130 rpm. Again, the air density
might have something to do with it. I'm also climbing out at about
90-100 rpm higher. It's a bitch to take down performance figures in
the cold air, and by the time the changes are made, the weather does
an "about face," and you have squat to compare to. Suffice it to say,
the engine runs good now, so be it air-straightening vanes or better
weather, I'm happy. One other thing I'm going to try...just for
kicks...is to swap the SCAT hose for some SCEET hose from airbox to
the vaned air duct. I just saw some SCEET hose, and that stuff is
smooth inside! For just a few bucks more per foot, I'm going for it.
After the initial flight today, I also changed to a 2.78 needle jet,
up from the original 2.76 jet. (I had done this a few weeks ago, but
changed float level too, and the combo had the engine stumbling, so I
removed it at the time) That didn't change the EGT's all that much,
but it did chase the hot EGT from #4 over to #3. I wasn't in the mood
to write down a bunch of figures at the time, but I will, and report
what I find.
My carb had the 2005 Economy Kit on board when I bought it, and the
jet and needle sizes were etched on the side of the carb. My needle
number ended in -1, meaning one groove, as I understand it, and
indeed it was a one-groove needle.
Lynn Matteson
Grass Lake, Michigan
Kitfox IV Speedster w/Jabiru 2200
flying w/490+ hrs
Message 2
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| Subject: | Re: EGTs and fuel quality |
Thanks for the input, Andy....I sure didn't know about, or probably
would not have thought about, the inner skin sucking in, but it makes
sense. I'll give that one some thought, but like you said, maintain
it and it'll probably be OK.
Lynn Matteson
Grass Lake, Michigan
Kitfox IV Speedster w/Jabiru 2200
flying w/490+ hrs
On Apr 20, 2008, at 12:43 PM, Andy Silvester wrote:
> <andy@suncoastjabiru.com>
>
> Lynn,
>
> Good work on the improvements! I'm sure many of us have found the same
> situation of not knowing *exactly* what brings better performance,
> especially when we are talking about a few % only, but those RPM
> increases
> are significant. A note about SCEET ducting; I've used it with
> success on
> the intake. Someone once told me that SCAT ducting has an equivalent
> resistance of 23, meaning that 1 foot of SCAT ducting has the same
> resistance to airflow as 23 feet of smooth-bore pipe! SCEET will be
> better,
> but bear in mind one down-side which I'm sure won't affect you. The
> inner
> 'skin' of the duct can perish and suck flat if given enough time
> and bad
> maintenance. It's a fair point, and a few A&Ps have told me it's a
> no-no to
> use it on anything below ambient pressure, i.e. a carburettor
> intake. My
> response (while being sympathetic to the argument) was that most
> Experimental aircraft get better maintenance than certificated types
> (!) and
> therefore the idea of a piece of duct not being internally
> inspected for
> (say) 5 years or more is less likely in our world (.....or is it??!!)
>
> Keep up the good work, Andy
>
> -----Original Message-----
> From: owner-jabiruengine-list-server@matronics.com
> [mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of
> Lynn
> Matteson
> Sent: 19 April 2008 14:36
> To: jabiruengine-list@matronics.com
> Subject: Re: JabiruEngine-List: Re: EGTs and fuel quality
>
> <lynnmatt@jps.net>
>
> Chuck-
> I just flew my newly-modified and installed air duct (from airbox to
> carb) and it works fine. I'd say great, but it didn't even out the
> EGT's like I hoped, but it did *seem* to give me more WOT rpm. Of
> course the weather has changed since I last checked for WOT rpm, but
> before I'd have to point the nose down just a little to get 3000 rpm.
> Today I could fly level and get 3130 rpm. Again, the air density
> might have something to do with it. I'm also climbing out at about
> 90-100 rpm higher. It's a bitch to take down performance figures in
> the cold air, and by the time the changes are made, the weather does
> an "about face," and you have squat to compare to. Suffice it to say,
> the engine runs good now, so be it air-straightening vanes or better
> weather, I'm happy. One other thing I'm going to try...just for
> kicks...is to swap the SCAT hose for some SCEET hose from airbox to
> the vaned air duct. I just saw some SCEET hose, and that stuff is
> smooth inside! For just a few bucks more per foot, I'm going for it.
>
> After the initial flight today, I also changed to a 2.78 needle jet,
> up from the original 2.76 jet. (I had done this a few weeks ago, but
> changed float level too, and the combo had the engine stumbling, so I
> removed it at the time) That didn't change the EGT's all that much,
> but it did chase the hot EGT from #4 over to #3. I wasn't in the mood
> to write down a bunch of figures at the time, but I will, and report
> what I find.
>
> My carb had the 2005 Economy Kit on board when I bought it, and the
> jet and needle sizes were etched on the side of the carb. My needle
> number ended in -1, meaning one groove, as I understand it, and
> indeed it was a one-groove needle.
>
> Lynn Matteson
> Grass Lake, Michigan
> Kitfox IV Speedster w/Jabiru 2200
> flying w/490+ hrs
>
>
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