monitoring temps in the engine compartment

I recently installed a Pmag replacing my right magneto and decided to explore temperatures within the engine compartment a bit before committing to adding a blast tube.

Armed with an infrared thermometer I had previously probed temperatures after shutdown on the magnetos, firewall, engine, and just about anything that I could reach and consistently saw highs around 165 near the engine with temperatures fading rapidly the farther away towards the firewall. The question of what kind of temperatures are there in flight was kicking around for me... with the Pmag installed I decided to find out.

The Dynon SkyView has two auxiliary contacts for thermocouples with the engine module (along with extra CHT and EGT contacts that can be used for a 5th and 6th cylinder).

The SkyView has built in tables to handle type J and K thermocouples. I poked around with Google for a bit and found several companies that specialize in temperature measurement that offered so many different probes it was like shopping for cereal at the grocery store. I ended up selecting a heavier gauge thermocouple wire terminated in a molded silicon end with 2 meter leads to give the most flexibility in moving them around and mounting them.





I used some silicon rescue tape to fasten one to the engine mount below the magneto in the exhaust stream from the oil cooler figuring that this might be the hottest spot and another I attached directly to the top of the Pmag.



The sensor has a foil tape on one side but it did not stick... I used some gorilla tape that was okay for testing but left some residue that needed to be cleaned up afterwards.



I also tried using some RTV to bed the sensor, but it did not setup well so I tested several more locations that were easier to mount to. After I finish exploring the temperature profile a bit more I will mount them more permanently.

What am I seeing for temperatures?
Lower than I expected in flight... at the Pmag the highest that I have seen was 144, with a stabilized modest cruise the temp was just 133. The hottest temp in flight was 165 under extended high cruise after climb at the oil cooler discharge area near the engine underneath the magneto. In the pattern and on final temperatures were down in the 110 range and stayed there by the Pmag during taxi but rose to 165 as a max at the oil cooler discharge (much lower in the engine as well).

Interesting to get this data and nice to have it displayed with my other engine data in flight. All of this testing so far has been with mild outside temperatures around 50 so I do expect to see things heat up quite a bit on our trip across country to sun-n-fun.

I have the same question on this for the magnetos and mecanical fuel pump to put or not blast tube or a shroud in the pump, so in my own opinion the shroud and the blast tubes isnt nessesary

Best Regards,

Stephen,
Great post, thank you ... good advertisement for Dynon Skyview as well, very impressive screen layout with a wealth of information!

I have a 'cowling air temp' reading on my Vision Microsystems EPI-800 with the temp senor near the oil cooler. I never see more than 71C/159F even on warm days in climb or cruise, typical numbers are around 65C/149F ... on the ground taxi back on really hot days I've seen up to 80C/176F.

Regarding blast tubes, I do not have one for the magneto (EI on the other side) but do have it going to the fuel pump on my Lyc IO-360.
Reggie

Cool. I wondered about the same thing. The FWF plans for the -10 do have you install a single blast tube for each magneto. However, i wondered what part of the magneto would you aim the blast of air since the magneto itself is fairly large compared to a 3/4" stream of air.

I do recall finding the mags themselves extremely hot after shutdown. Much much too hot to touch. One day I need to measure the temp of the magneto with an IR temp gun to get some hard numbers and see if they match your finding.

Jae

I have temp labels on mags, fuel pump, alternator and starter. Alternator reads 300F due to radiant exhaust heat from #1. This does not mean internal temp reached that, otherwise it would not be generating 55-59 amps after start up charging two odyssey batteries. Fuel pump has reached 225F but this label was not in direct view of #6 exhaust. I did recall having low fuel pressure reading at idle a few flights back after hot start and then was fine after boost pump was turned on for 15 sec and back off.

I also installed 250F furnace limit switch near cowl outlet to energize an led on the panel in case of fire. You may not realize there is a fire until flames come through the floor. Max temp flown so far was 80F. I did not install mag or alt blast tubes. I will see how the 250F limit does this summer.