Hi, Robert-
Sorry to be so slow at entering this conversation. Been laid up for several weeks with knee replacement surgery and just beginning to get my life back.
I installed a JPI EDM 830 a year ago in my '59-250. Placed the OAT probe mid-way up the pilot's side of the fuselage, an inch or two aft of the firewall. I can heartily recommend AGAINST placing it there, at least not on an early 250 with the big muffler running across the front of the firewall. Prior to startup, the EDM readout agrees with the old original "meat thermometer" probe. Once all the engine temps have stabilized and one is cruising in level flight, the JPI probe consistently reads 1 - 2 degrees C HIGHER than the original probe. (That's right - I kept the original probe. Redundancy is a nuisance until you really wish you had it.) I suspect the JPI probe is picking up some engine compartment heat due to its location. It is an unfortunate annoyance having to apply a correction to all the readings, particularly since I have the 830 wired into my Garmin 530W.
If any questions, give me a call at (403) 823-0405 or
c-flhv@magtech.caDon Ostergard, Drumheller AB