hgerhardt
Well Known Member
Now that PlaneKool is working so well, I’ve been venturing into warmer locales where pre-A/C, I just didn’t bother to fly. But now, oil temps are making regular excursions to 225*+ F. I set up a test by using my Bluetooth HVACR refrigerant line temp probes to measure oil cooler (OC) inlet/outlet temps and compared those to indicated on my G3X. During warmup, I saw that the OC inlet was measuring within 3*F of indicated, which gave me some confidence of the BT probe’s accuracy with the less-than-ideal clamp arrangement on a hex nut. Found that indicated temp was only 6*F cooler than OC inlet temp and that there was 16F delta of OC inlet/outlet, indicating the Vernatherm (VT) wasn’t doing a good job. Problem found! Or so I thought…
Vernatherm Testing
Set up a water bath using a sous-vide heater and a height gage with a home-made ring gage, the dimensions of which I got from Lycoming SI 1316A and tested the 12-yr-old, 750-hr VT together with the original to the engine from 1980 and found the newer one didn’t even extend far enough to completely close the port. Bought a new VT, retested and made a bar graph of the results; points within the upper left quad are good. The red vertical line is design temp to close the port fully and the blue line is extension length to close the port. The original 1980 one was better than the 2008, but the new one is dramatically better. Problem solved! Or so I thought…
Vernatherm Seat Repair
Installed the new VT and flight-tested it. Not a huge amount of improvement (7F delta of OC inlet vs indicated, where previously it had been 6F). Thought about it and went back and looked at the 2008 VT and to me the seat was possibly leaking at the VT cone. I had checked the VT seat in the engine with a (low-quality) endoscope before I replaced the VT and it looked OK… however, after inspecting the 2008 VT, I saw the cone didn’t have even wear on its face. Time to clean up the seat per that same SI 1316A. The tool called out to remachine the seat is available to buy for… $2100! You gotta be kidding me… fortunately I had a couple of dead VT’s available, so I made my own from one of those plus $40 of parts from McMaster and 10 min on a lathe.
Cleaned up the seat and checked for any loose chips and went for a flight.
Results were better, but still not where I thought it should be, with 11F inlet/indicated delta. Time to do some more thinking…
Which brings us to: Ducts Matter
Vernatherm Testing
Set up a water bath using a sous-vide heater and a height gage with a home-made ring gage, the dimensions of which I got from Lycoming SI 1316A and tested the 12-yr-old, 750-hr VT together with the original to the engine from 1980 and found the newer one didn’t even extend far enough to completely close the port. Bought a new VT, retested and made a bar graph of the results; points within the upper left quad are good. The red vertical line is design temp to close the port fully and the blue line is extension length to close the port. The original 1980 one was better than the 2008, but the new one is dramatically better. Problem solved! Or so I thought…
Vernatherm Seat Repair
Installed the new VT and flight-tested it. Not a huge amount of improvement (7F delta of OC inlet vs indicated, where previously it had been 6F). Thought about it and went back and looked at the 2008 VT and to me the seat was possibly leaking at the VT cone. I had checked the VT seat in the engine with a (low-quality) endoscope before I replaced the VT and it looked OK… however, after inspecting the 2008 VT, I saw the cone didn’t have even wear on its face. Time to clean up the seat per that same SI 1316A. The tool called out to remachine the seat is available to buy for… $2100! You gotta be kidding me… fortunately I had a couple of dead VT’s available, so I made my own from one of those plus $40 of parts from McMaster and 10 min on a lathe.
Cleaned up the seat and checked for any loose chips and went for a flight.
Results were better, but still not where I thought it should be, with 11F inlet/indicated delta. Time to do some more thinking…
Which brings us to: Ducts Matter