Today's Message Index:
----------------------
1. 12:14 AM - Tiger Annual update. (TeamGrumman@AOL.COM)
2. 07:08 AM - Re: Tiger Annual update. (FLYaDIVE@AOL.COM)
3. 09:27 AM - Re: Cowling Update. 8.0 (bhauskne@san.rr.com)
4. 11:38 AM - (TeamGrumman@AOL.COM)
5. 06:08 PM - Re: Tiger Annual update. (TeamGrumman@AOL.COM)
Message 1
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| Subject: | Tiger Annual update. |
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
I mentioned a Tiger that came in for an annual.
I took the cylinders to LyCon for inspection. No serious cracks, just some
small stress cracks. That was the good news. The bad news was that the
valve guides were all blown out. To the tune of 0.020. Several exhaust valves
had sunk into the head quite a way. Ken said it looked like the engine had
been running on auto fuel. ALL of the intakes were tulipped; that is, they
had been run so hot that they were deformed. Ken said it looked like the
engine had been run real lean.
However. The owner has placed this plane on lease back and placarded the EI
CHT/EGT gauge to say " DO NOT LEAN for an EGT HIGHER THAN 1200 degrees. "
or something to that effect. When I asked him about it, he said if the EGTs
were kept the CHTs would be cool. Nice in theory.
My experience is that a rich mixture has very little effect on keeping the
CHTs down. Mixture has a big effect on EGT though.
The cylinders in question have less than 600 hours on them. And, they are
trashed. #3 was pulled at 200 hours and had the valves reground and
reinstalled. These cylinders WERE new ECI cylinders with Cermi-Nil. The cylinders
had
0.003 choke. It's supposed to be 2-3 times that. All of these cylinders
had a lot of excess flashing between the fins. The area between the valves
(under the plug) was about 70-80% blocked off by flashing. The spaces between
the fins on the head otherwise were also partially blocked with flashing.
Add to this very poor baffling and I think this engine had been run really hot
for a long time.
I suspect that even though the EGT was kept below 1200, the CHTs were high
enough to cause serious damage to the engine. I discussed with Ken the
possibility of instrumenting a head to measure the exhaust valve guide temperature.
I would be curious to see if a mixture lean enough to make the CHT go down
and the EGT to peak would make the guide temperature to go down. Maybe even
install several EGT probes in the riser and exhaust pipe to see if the high EGT
is across the length of the pipe or more localized.
Just to recap. I leaned aggressively during a takeoff from Bakersfield a
few weeks ago and brought the CHTs down from 440+ to 417. The temp difference
between the 4 CHTs was less than 2 degrees. Ken (at LyCon) could not be
pinned down as to whether the lower CHT was helping the valve guides or not.
Does anyone have an idea how to measure the temp on the face of a valve while
it's running?
Gary
Message 2
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| Subject: | Re: Tiger Annual update. |
--> TeamGrumman-List message posted by: FLYaDIVE@aol.com
In a message dated 10/29/04 3:15:00 AM Eastern Daylight Time,
TeamGrumman@AOL.COM writes:
> --> TeamGrumman-List message posted by: TeamGrumman@aol.com
>
> I mentioned a Tiger that came in for an annual.
>
> I took the cylinders to LyCon for inspection. No serious cracks, just
some
> small stress cracks.
----------------------
Where were the stress cracks? Are they visible with out Die Penetrant
Inspection?
=================================================
That was the good news. The bad news was that the
> valve guides were all blown out. To the tune of 0.020. Several exhaust
> valves had sunk into the head quite a way. Ken said it looked like the
engine had been running on auto fuel. ALL of the intakes were tulipped; that
is, they
> had been run so hot that they were deformed. Ken said it looked like the
> engine had been run real lean.
------------------------------------------
WHO'S make cylinders were they - Manufacture?
ECI and Superior have stated that the valve seat material has been changed so
as to handle MoGas.
And it is a known fact that Lycoming has had SOFT castings which will result
in valve seats sinking into the cylinder.
=============================================
> However. The owner has placed this plane on lease back and placarded the
> EI CHT/EGT gauge to say " DO NOT LEAN for an EGT HIGHER THAN 1200 degrees.
" or something to that effect. When I asked him about it, he said if the
> EGTs were kept the CHTs would be cool. Nice in theory.
>
> My experience is that a rich mixture has very little effect on keeping the
> CHTs down. Mixture has a big effect on EGT though.
>
> The cylinders in question have less than 600 hours on them. And, they
are
> trashed. #3 was pulled at 200 hours and had the valves reground and
> reinstalled. These cylinders WERE new ECI cylinders with Cermi-Nil.
The
> cylinders had 0.003 choke. It's supposed to be 2-3 times that. All of
these
> cylinders had a lot of excess flashing between the fins. The area
between the valves
> (under the plug) was about 70-80% blocked off by flashing. The spaces
> between the fins on the head otherwise were also partially blocked with
flashing.
> Add to this very poor baffling and I think this engine had been run really
> hot for a long time.
-----------------------------------------------
AHhhhh BINGO ... POOR BAFFLING and BAD FLASHING ... That will do it all the
time.
BUT! I thought ECI had one of the BETTER castings on the market along with
Superior. Were these ECI cylinders or just REWORKED cylinders by ECI?
Is this a fact: ECI does Cermi-Nil? I was not aware of that. I thought
their calm to fame was they do either Through Hardening (Flame Hardening) or
Nitrating?
================================================
> I suspect that even though the EGT was kept below 1200, the CHTs were high
> enough to cause serious damage to the engine. I discussed with Ken the
> possibility of instrumenting a head to measure the exhaust valve guide
> temperature.
> I would be curious to see if a mixture lean enough to make the CHT go down
> and the EGT to peak would make the guide temperature to go down. Maybe
> even install several EGT probes in the riser and exhaust pipe to see if the
high
> EGT is across the length of the pipe or more localized.
>
> Just to recap. I leaned aggressively during a takeoff from Bakersfield a
> few weeks ago and brought the CHTs down from 440+ to 417. The temp
> difference between the 4 CHTs was less than 2 degrees. Ken (at LyCon)
could not be pinned down as to whether the lower CHT was helping the valve
guides or not.
>
> Does anyone have an idea how to measure the temp on the face of a valve
> while it's running?
NO WAY in this world. But! Why not clamp a thermocouple wire to the Stem of
the valve and one next to depression of the valve guide and casting. Coat
both with RTV to isolate them from the Oil Temp. The readings you get will
answer EGT Vs CHT temperatures... My money is on, EGT increases - CHT increases.
If the heat inside the cylinder increases because of leaning the CHT will
increase.
BUT!!! If the CHT increases due to Detonation you will see a small increase
in EGT. That is because detonation occurs before the normal firing cycle and
the exhaust ports are open allowing the burnt gases to escape over a longer
period of time.
As for High/Low temps helping or hurting valve guides ... That would depend
on what material is being used for the guide and whether expansion of the
material is used to aid in the valve clearance.
Operational valve clearance during operation is not the same as with the
Valve Wobble Test. MOST ... NOT ALL ... materials expand with heat. So the
clearance you see during the SB388 is not what the engine sees during operation.
If you can find out EXACTLY the type of material the guide is made from you
can go to a material web site and determine the coefficient of expansion both
linear and transverse.
Barry
"Chop'd Liver
===================================================
>
> Gary
Message 3
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| Subject: | Cowling Update. 8.0 |
--> TeamGrumman-List message posted by: "bhauskne@san.rr.com" <bhauskne@san.rr.com>
>> I'll be interesting. For sure.
Yes, yes you are! Looking forward to hearing the results on the latest
version. Are you approaching the "Gold" release that may actually be STC'd
and sold?
--Brian
Tiger N28289
Message 4
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--> TeamGrumman-List message posted by: TeamGrumman@aol.com
Yes, yes you are! Looking forward to hearing the results on the latest
version. Are you approaching the "Gold" release that may actually be STC'd
and sold?
I'll keep you posted
Message 5
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| Subject: | Re: Tiger Annual update. |
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
In a message dated 10/29/04 7:11:02 AM, FLYaDIVE@AOL.COM writes:
> Where were the stress cracks?=A0 Are they visible with out Die Penetrant
> Inspection?
>
yes, they were visable to the eye. They lightly sand blasted the surface.
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