Quote:
Originally Posted by new2subaru
Why would you expect your oil to be below water temps? 200F is not to be expected with any cooler.
I've read that the stand alone oil cooler is "better" but haven't seen any evidence as to why.
I've also read people praising the JR combo, so, yeah...
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Okay, here goes some theory-craft based on thermodynamics:
Cooling efficiency depends on a couple of factors and the biggies are 1. surface area and 2. temperature differences between the hot and cold places.
Both the coolant and the oil share responsibility for cooling the engine, so with the heat exchanger you're dumping the cooling responsibility of the oil into the coolant and if you don't increase the efficiency of your radiator (make it bigger, add more fins, etc) you'll just max out the radiator faster under heavy load. Water/coolant can retain lots of heat but that's a double edged sword, and once you've started to boil your coolant you're going to have a bad day. If you go with the heat exchanger, you'll need to upgrade your radiator and fans to see any significant benefits at the track.
With an air to oil OC, you've added extra surface area to cool stuff off and since the oil is hotter than the coolant, more heat is shed with the same radiator area (one of the reasons why OC's are smaller than radiators). The oil also retains less heat than water/coolant and changes temperature faster (lower specific heat and density). Adding a "normal" oil cooler is all you have to do to get the desired benefits.
Both strategies can be viable as long as you are aware of your needs and the limitations of whichever you choose. If you don't want or need to upgrade your radiator, the air to oil coolers are the way to go; however, if you are in the process of replacing or upgrading your radiator anyway you could get away with a Forester type heat exchanger (the heat exchangers also help heat cold oil up to operating temps faster, whereas the other type will increase the warm up times).