---------------------------------------------------------- TeamGrumman-List Digest Archive --- Total Messages Posted Fri 10/29/04: 5 ---------------------------------------------------------- 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 _____________________________________ Time: 12:14:15 AM PST US From: TeamGrumman@AOL.COM Subject: TeamGrumman-List: 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 _____________________________________ Time: 07:08:28 AM PST US From: FLYaDIVE@AOL.COM Subject: Re: TeamGrumman-List: 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 _____________________________________ Time: 09:27:42 AM PST US From: "bhauskne@san.rr.com" Subject: RE: TeamGrumman-List: Cowling Update. 8.0 --> TeamGrumman-List message posted by: "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 _____________________________________ Time: 11:38:27 AM PST US From: TeamGrumman@AOL.COM --> 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 _____________________________________ Time: 06:08:21 PM PST US From: TeamGrumman@AOL.COM Subject: Re: TeamGrumman-List: 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.