Originally Posted by Carlito2002WGN
IF these plates actually make a difference, I don't think that it would be in lower coolant temps, but rather in more efficiently lowering the coolant temp down to where it would be anyway due to the thermostat, from high temps that could result from high ambient temps and high load.
For street driving, one of these almost certainly will never be necessary. They do look nice, and I'm all about efficiency, particularly when it can be done cheaply.
If you are subjecting the engine to prolonged high loads (in other words, track days), you'll need to optimize the cooling system. Even with my N/A EJ25 the coolant temp stabilizes about 25degF above the thermostat when I do track events, and that's with an undertray and radiator shroud that both helped control temps. On my track-prepped Mustang I have the radiator almost fully boxed in so that air has no path to escape around the sides. It really starts to make a difference when you're flogging the car hard for 20 or 30min at a time.