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bbradburry(at)bellsouth.n
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 Posted: Wed Sep 02, 2009 8:11 am Post subject: rigging a thermocouple on a certified plane |
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My son owns a Mooney. He can not lean it past about 50-100 degrees rich of
peak with out it starting to miss. He is burning about 12 Gal/Hr at cruise
when I think he should be able to get to about 10. He could benefit from
some type of injector balancing like from GAMI. Problem is he doesn't have
the necessary EGT probes to get the information for each cylinder and
installing a certified rig to do this would be too expensive.
My thought is that he could clamp probes to the outside of the exhaust
manifold tubes for each cylinder and run them to a reader head in the
cockpit to get "close enough" information for this application. I have
thermocouple wire and could make the probes. Where could he come upon an
inexpensive reader head for thermocouples.
What is the community take on this? Would it work? Is it legal if it is not
permanently attached to the plane?
Name withheld to protect the currently innocent! :>)
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stein(at)steinair.com
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| Posted: Wed Sep 02, 2009 8:54 am Post subject: rigging a thermocouple on a certified plane |
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Hi Bill,
My take would be that you're flying a Mooney - it's not an Ercoupe (meaning
it's not a super cheap airplane to begin with). It cost about $1600 to get
one of the best systems out there (Electronics International), or you can go
cheaper and get a JPI for about $1300. If you start down the GAMI path it's
not going to be cheap anyway...I'd spend the bucks and get a good EGT/CHT
monitor. If you want to keep the engine happy and fly it right, you should
have one anyway....just to see what the engine is doing. Why go through all
the work of balancing the cylinders with some cobbled together system, only
to remove it later?? Makes little sense to me, but that's just my opinion.
My 2 cents as usual.
Cheers,
Stein
_________________________________________
The information transmitted is intended only for the person or entity to
which it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you receive
this in error, please contact the sender and delete the material from any
computer.
[quote]--
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mprather(at)spro.net
Guest
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| Posted: Wed Sep 02, 2009 9:11 am Post subject: rigging a thermocouple on a certified plane |
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Here's a dedicated K-type meter:
http://www.virtualvillage.com/digital-thermometer-for-k-type-thermocouples/sku003920-016
If the above wraps, try this:
http://tinyurl.com/kloqam
Matt-
| Quote: |
<bbradburry(at)bellsouth.net>
My son owns a Mooney. He can not lean it past about 50-100 degrees rich
of
peak with out it starting to miss. He is burning about 12 Gal/Hr at
cruise
when I think he should be able to get to about 10. He could benefit from
some type of injector balancing like from GAMI. Problem is he doesn't
have
the necessary EGT probes to get the information for each cylinder and
installing a certified rig to do this would be too expensive.
My thought is that he could clamp probes to the outside of the exhaust
manifold tubes for each cylinder and run them to a reader head in the
cockpit to get "close enough" information for this application. I have
thermocouple wire and could make the probes. Where could he come upon an
inexpensive reader head for thermocouples.
What is the community take on this? Would it work? Is it legal if it is
not
permanently attached to the plane?
Name withheld to protect the currently innocent! :>)
|
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mprather(at)spro.net
Guest
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| Posted: Wed Sep 02, 2009 9:11 am Post subject: rigging a thermocouple on a certified plane |
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|
It sounds like you might have a malfunction in either the ignition or fuel
delivery systems on the engine. Maybe an air leak (around an intake tube
where it goes into the sump)? Does the fuel flow match what's published
in the operating manual for the airplane?
I can't speak to the legality of temporarily installing additional
instrumentation. My guess is that if it were battery powered or driven by
the cigar lighter there wouldn't be a problem. Likely nobody wouldn't
find out unless the airplane were involved in an accident while the system
were in the airplane.
Functionally, the temperature measured would be slightly more dependent on
the CHT than would a properly installed EGT probe, as the exhaust stacks
are cooled by their attachment to the cylinders. Regardless, I think you
might get useful data. Depending on how little wiring and soldering you
want to do, it could be fairly clunky to use, but as a diagnostic tool,
temporarily installed, it should be effective enough.
Another thought is that the probes are the 'cheap' part of the certified
system, and the display is the expensive part. Install the probes, and
then use a temporary instrument to read the data from them..
To read the data, I know it's fairly common for the cheap Harbor Freight
multimeters to include an input and display mode for a thermocouple probe.
I can't recall the wire type that mine is designed for, but I'd think it
would be perfectly adequate. Keep in mind, the absolute accuracy isn't
all that important. You need decent repeatability only. The only thing
you really need to find is the order in which each cylinder reaches peak
EGT. The first to peak is the leanest cylinder, and the last to peak is
the richest.
Here's a mutlimeter from Harbor Freight that includes input for a
temperature probe.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=37772
You could choose to install some sort of switching system (Aircraft Spruce
sells a rotary switch), or you could just route all of the probe leads
into the cockpit and plug each one into the meter in turn and record the
necessary data.
If you are really ambitious, and your time isn't worth that much, Analog
Devices makes an IC designed to read thermocouples. You could use these
IC's in a home grown meter..
BTW, how do the spark plugs look?
Matt-
| Quote: |
<bbradburry(at)bellsouth.net>
My son owns a Mooney. He can not lean it past about 50-100 degrees rich
of
peak with out it starting to miss. He is burning about 12 Gal/Hr at
cruise
when I think he should be able to get to about 10. He could benefit from
some type of injector balancing like from GAMI. Problem is he doesn't
have
the necessary EGT probes to get the information for each cylinder and
installing a certified rig to do this would be too expensive.
My thought is that he could clamp probes to the outside of the exhaust
manifold tubes for each cylinder and run them to a reader head in the
cockpit to get "close enough" information for this application. I have
thermocouple wire and could make the probes. Where could he come upon an
inexpensive reader head for thermocouples.
What is the community take on this? Would it work? Is it legal if it is
not
permanently attached to the plane?
Name withheld to protect the currently innocent! :>)
|
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ainut(at)hiwaay.net
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ainut(at)hiwaay.net
Guest
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| Posted: Wed Sep 02, 2009 11:30 am Post subject: rigging a thermocouple on a certified plane |
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|
We're using the Analog Devices thermocouple IC's and it's not really all
that hard if you use their engineering advice. Very inexpensive, too.
You can bring the outputs of their IC's (AD 494 and AD 495) to feed many
types of readers. We bring the 0-5v into a Labjack USB input into a
laptop for logging and trending. The Labjack U12 is the older model but
that's what we use. It's around $100. There are even cheapers ways to
do the A/D but they take a *lot* more time and engineering.
David M.
Matt Prather wrote:
| Quote: |
It sounds like you might have a malfunction in either the ignition or fuel
delivery systems on the engine. Maybe an air leak (around an intake tube
where it goes into the sump)? Does the fuel flow match what's published
in the operating manual for the airplane?
I can't speak to the legality of temporarily installing additional
instrumentation. My guess is that if it were battery powered or driven by
the cigar lighter there wouldn't be a problem. Likely nobody wouldn't
find out unless the airplane were involved in an accident while the system
were in the airplane.
Functionally, the temperature measured would be slightly more dependent on
the CHT than would a properly installed EGT probe, as the exhaust stacks
are cooled by their attachment to the cylinders. Regardless, I think you
might get useful data. Depending on how little wiring and soldering you
want to do, it could be fairly clunky to use, but as a diagnostic tool,
temporarily installed, it should be effective enough.
Another thought is that the probes are the 'cheap' part of the certified
system, and the display is the expensive part. Install the probes, and
then use a temporary instrument to read the data from them..
To read the data, I know it's fairly common for the cheap Harbor Freight
multimeters to include an input and display mode for a thermocouple probe.
I can't recall the wire type that mine is designed for, but I'd think it
would be perfectly adequate. Keep in mind, the absolute accuracy isn't
all that important. You need decent repeatability only. The only thing
you really need to find is the order in which each cylinder reaches peak
EGT. The first to peak is the leanest cylinder, and the last to peak is
the richest.
Here's a mutlimeter from Harbor Freight that includes input for a
temperature probe.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=37772
You could choose to install some sort of switching system (Aircraft Spruce
sells a rotary switch), or you could just route all of the probe leads
into the cockpit and plug each one into the meter in turn and record the
necessary data.
If you are really ambitious, and your time isn't worth that much, Analog
Devices makes an IC designed to read thermocouples. You could use these
IC's in a home grown meter..
BTW, how do the spark plugs look?
Matt-
>
> <bbradburry(at)bellsouth.net>
>
> My son owns a Mooney. He can not lean it past about 50-100 degrees rich
> of
> peak with out it starting to miss. He is burning about 12 Gal/Hr at
> cruise
> when I think he should be able to get to about 10. He could benefit from
> some type of injector balancing like from GAMI. Problem is he doesn't
> have
> the necessary EGT probes to get the information for each cylinder and
> installing a certified rig to do this would be too expensive.
> My thought is that he could clamp probes to the outside of the exhaust
> manifold tubes for each cylinder and run them to a reader head in the
> cockpit to get "close enough" information for this application. I have
> thermocouple wire and could make the probes. Where could he come upon an
> inexpensive reader head for thermocouples.
> What is the community take on this? Would it work? Is it legal if it is
> not
> permanently attached to the plane?
>
> Name withheld to protect the currently innocent! :>)
------------------------------------------------------------------------
Checked by AVG - www.avg.com
|
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khorton01(at)rogers.com
Guest
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| Posted: Wed Sep 02, 2009 2:57 pm Post subject: rigging a thermocouple on a certified plane |
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|
On 2 Sep 2009, at 12:10, Bill Bradburry wrote:
| Quote: |
>
My son owns a Mooney. He can not lean it past about 50-100 degrees
rich of
peak with out it starting to miss. He is burning about 12 Gal/Hr at
cruise
when I think he should be able to get to about 10. He could benefit
from
some type of injector balancing like from GAMI. Problem is he
doesn't have
the necessary EGT probes to get the information for each cylinder and
installing a certified rig to do this would be too expensive.
My thought is that he could clamp probes to the outside of the exhaust
manifold tubes for each cylinder and run them to a reader head in the
cockpit to get "close enough" information for this application. I
have
thermocouple wire and could make the probes. Where could he come
upon an
inexpensive reader head for thermocouples.
What is the community take on this? Would it work? Is it legal if
it is not
permanently attached to the plane?
|
I predict that the response time of thermocouples clamped to the
outside of the exhaust pipes would be so slow as to make them
essentially useless. I won't comment on legality.
It sounds like you are spending a lot more on fuel than would be
needed if the aircraft was running correctly. Given the cost of this
extra fuel, and the cost of top overhauls if you cook a cylinder(s)
due to poor EGT data, I recommend you spend the bucks to install an
approved, reasonable quality four cylinder EGT and CHT system. It
would likely prove to be a false economy to go too cheap here.
Good luck.
--
Kevin Horton
RV-8 (Flight Test Phase)
Ottawa, Canada
http://www.kilohotel.com/rv8
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Wed Sep 02, 2009 4:10 pm Post subject: rigging a thermocouple on a certified plane |
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There is something definitely wrong with the engine, assuming it is
Lycoming 200hp fuel injected. Many 200hp Mooneys will run fine LOP with
stock injectors. I'd be looking at plugs, mags and injectors for
starters. Also, a wobble check on the exhaust valves, and a leak check
on the intake tubes.
If it is the 180hp carbureted engine, check for intake leaks, and try
some carb heat to help.
SteinAir, Inc. wrote:
[quote]
Hi Bill,
My take would be that you're flying a Mooney - it's not an Ercoupe (meaning
it's not a super cheap airplane to begin with). It cost about $1600 to get
one of the best systems out there (Electronics International), or you can go
cheaper and get a JPI for about $1300. If you start down the GAMI path it's
not going to be cheap anyway...I'd spend the bucks and get a good EGT/CHT
monitor. If you want to keep the engine happy and fly it right, you should
have one anyway....just to see what the engine is doing. Why go through all
the work of balancing the cylinders with some cobbled together system, only
to remove it later?? Makes little sense to me, but that's just my opinion.
My 2 cents as usual.
Cheers,
Stein
_________________________________________
The information transmitted is intended only for the person or entity to
which it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you receive
this in error, please contact the sender and delete the material from any
computer.
> --
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD |
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mprather(at)spro.net
Guest
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| Posted: Wed Sep 02, 2009 4:15 pm Post subject: rigging a thermocouple on a certified plane |
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Kevin,
I agree that compared to buying engine parts, instrumentation is a fair
deal. However, certainly people were able to diagnose engine malfunction
before multipoint CHT/EGT existed. If the POH says the engine should be
able to do something that this engine isn't doing, a good mechanic should
be able to track it down.
Regards,
Matt-
| Quote: |
<khorton01(at)rogers.com>
On 2 Sep 2009, at 12:10, Bill Bradburry wrote:
>
> <bbradburry(at)bellsouth.net
> >
>
> My son owns a Mooney. He can not lean it past about 50-100 degrees
> rich of
> peak with out it starting to miss. He is burning about 12 Gal/Hr at
> cruise
> when I think he should be able to get to about 10. He could benefit
> from
> some type of injector balancing like from GAMI. Problem is he
> doesn't have
> the necessary EGT probes to get the information for each cylinder and
> installing a certified rig to do this would be too expensive.
> My thought is that he could clamp probes to the outside of the exhaust
> manifold tubes for each cylinder and run them to a reader head in the
> cockpit to get "close enough" information for this application. I
> have
> thermocouple wire and could make the probes. Where could he come
> upon an
> inexpensive reader head for thermocouples.
> What is the community take on this? Would it work? Is it legal if
> it is not
> permanently attached to the plane?
I predict that the response time of thermocouples clamped to the
outside of the exhaust pipes would be so slow as to make them
essentially useless. I won't comment on legality.
It sounds like you are spending a lot more on fuel than would be
needed if the aircraft was running correctly. Given the cost of this
extra fuel, and the cost of top overhauls if you cook a cylinder(s)
due to poor EGT data, I recommend you spend the bucks to install an
approved, reasonable quality four cylinder EGT and CHT system. It
would likely prove to be a false economy to go too cheap here.
Good luck.
--
Kevin Horton
RV-8 (Flight Test Phase)
Ottawa, Canada
http://www.kilohotel.com/rv8
|
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and are quite reasonable in prices.
