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I took N6XE in for it's annual Topcare Inspection yesterday and today it is getting 6 new cylinders.
It started and ran just perfect and very smooth. I wanted to record some temperatures on the 35 min. flight to Lycon in Visalia, CA. so I took off and left it at full power for a while, leveled at 4K ft. and saw 210 Kts. IAS and 227 TAS. The highest CHT I saw was #2 at 402*. It was pumping 43.6 GPH all the EGT's and CHT's were as normal. Max EGT was 1411* at that full flow. When we took the compression it was three at 54/56 and three at 24/44 over 80 Lbs. Not good, and hearing some leakage in the exhaust. "Oh Shit" was the mechanic's response so I said the same and authorized the removal of the cylinders.
How I operated the engine? I broke the engine in hard and changed the first oil at 10 hrs. Then again at 40 hrs, or 30 on that oil. I changed it every 30 to 37 hrs. The Oil Analysis started showing high Iron and Nickel the time before the last analysis and the last one taken at 200 hrs or 15 hrs ago showed less Iron and Nickel then before but still high. I did operate Lean Of Peak and wanted to explain that in detail.
First off I am a Mechanical Engineer and an old Drag racer mechanic before getting my degree, so I take full responsibility. I have done everything to engines that could be done in the past and fully understand what is going on in the engine AND I know the risk / benefit of, LOP, temperatures, Fuel flow, and etc. I have read/copied George B. GAMI's every email and read and tried all there information, making be a believer. However, this engine did NOT have GAMI's. The TCM factory says that this engine was designed to run LOP and this one ran perfect while lean. I have the SFS EFIS and a third screen so I watched the engine very close. My biggest operational problem was keeping #2 cylinder below 410*while ROP in the climb. This was hard while on the rich side and frequently required HI Boost while in the climb to FL 250. Then I would go LOP while cruising and usually ran 1 inch. more MP than one would on the rich side. Normal cruise was 32.5/ 2500 or 2400 LOP, and climb at 33/2550 or 2600 ROP. I did lots of things to try an improve the cooling air on #2 but when it reached 420* I would use Hi Boost or lower MP or go LOP if it didn't come down. I adjusted the Fuel Flow aneroid to keep the full take off power FF over 42 but mostly up to 44 GPH. Noteworthy is that #2 cyl. was the CHT that I watched most and it had the highest compression, 56. #6 cyl., front left, was the lowest at 24 lbs. Lycon does not recommend running LOP and told me that last year. They have seen it all and even TCM calls the exhaust valve failure "Valve Stretch." This is what we expect to find when the Cyl. are removed. (I will report). The thought is that when LOP there is not enough LEAD left in 100 LL to adequately lubricate the exhaust valve stem and guide. TCM uses steel guides on the exhaust I'm told. If they are cast Iron they may have some self lubing but I don't know the material spec. I think most car engines that now use No lead have gone to a Phosphor Bronze material and maybe powdered metal to become more self lubing and hold oil. I'm not sure about this material stuff but it looks like this is the weak point on this engine running LOP. I had decided that if I got 500 hrs or more before I needed a top overhaul that LOP would be OK. Now I will have to go back to ROP and lower the MP until someone comes out with better material for valve guides and seats. By then I will have the choice of putting in the TPE 331-10 with 1000 HP and 7500 hr TBO.
Grounded,
Jim Hergert
N6XE, "An Sex Y" L4P
Flew back in a C150 in 1hr 45 min. making my first landing in one of these in 35 years---in The Dark. I'll take my L4P even with 6 weak Cyl.'s thank you.
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