no surprise...
...that different manufacturers publish difference performance numbers, but I was surprised at the amount of the difference. On the graph from Scott's link there are 4 oil coolers shown. Here are the models and their heat rejection numbers based on an assumed 5" H20 pressure across the air side, along with what other sources say. All values in BTU/min/100F inlet temp difference.
Positech 20002C 335, Aero Classics graphs say 150
SW 8406 308 SW's graphs show 290
Aero 8000075 258, Aero Classics says 270
NDM 20002A 255, Aero Classics says 270
Most are pretty close except for the first one where Positech's number is more than twice what Aero Classics says. That's huge especially since 150 BTU/min is way too little for Lyc 360's. One of them has to be wrong.
I'd ask for everyone's experiences but without knowing some real numbers it would all be anecdotal evidence and with oil coolers that does not help much. I think too much has to do with where and how it's mounted (baffle or firewall) if it is set back from the baffle, and most especially the quality of the baffle and seals or a plenum.
Lycoming says the heat that needs to be removed is "not to exceed" 475 BTU/min. Assuming 100F inlet air and 250F inlet oil, that is equivalent to about 316 BTU/min/100F. According to Positech's graphs, their 20002C is the only one of these 4 to meet that criteria.
As I said above, I'm finishing installing a Aero Classics 8000081 today or this week, depending on how the rest of it goes. According to the Aero Classics data, that oil cooler should reject about 365 BTU/min/100F. I'll let everyone know how it goes but without being able to measure the inlet and outlet oil temperatures and the pressure differential on the air side I won't be able to verify their numbers. I have some ideas on how to instrument the cooler but that will have to wait until I have more time.
