I don't know what the NACA ducts on the 47 are for (for that matter, I don't know what the ducts on a Ferrari 308 GTB or any number of cars are for) but I do know that the vents in the TC engine cover suck air from the engine compartment into the area behind the rear window. I think the S2 is similar but the screen between the tail/brake/backup lights could alter things. Here is a video I took of the air flow in my car (
https://www.youtube.com/watch?v=aqHFg4q7jxA). I had figured that a low pressure area would form behind the back of the car but the area behind the rear window provides a much stronger low pressure area (
https://www.youtube.com/watch?v=1L4F4dEc2BQ). Possibly, if it weren't for the engine cover vents, the rear would have a stronger low pressure area.
I also understand that, as counter intuitive as it seems given the previous paragraph, that the snorkels are designed to provide cold air for the carbs actually do the job for which they are intended. In fact, a member here (Sandyman) made his own snorkel that seemed to cool the engine compartment and presumably also cool the intake charge. Here is part of a thread that discusses that (
http://www.lotuseuropa.org/LotusForum/index.php?topic=3062.msg57530#msg57530). For intake charge cooling, there are other options. One that is very effective is to snake the intake air cleaner down near the bottom of one of the fuel tanks. Here's a thread (there may be others) about it including a pdf attachment describing how our own pboedker did his (
http://www.lotuseuropa.org/LotusForum/index.php?topic=2658.0). Since I have to guess, I would guess that the NACA ducts on the 47 provide a similar function to the snorkels...
I think the idea for the radiator is put it on one side to make room for a spare tire and jack. I would also guess that Lotus sized it and decided in front of the right front tire was a good place for it. People with more aggressive engines sometimes put a larger radiator that exhausts out the top of the bonnet. This is efficient but I would imagine their spare tire is a tire patch kit and battery operated compressor or a bottle of Slime.
As I stated before, I assumed that the car would form a low pressure area behind the car so that's where I put my oil cooler. That turned out to be a mistake. An oil cooler would be better placed in front of the radiator or if you really want to get fancy, you could fence off some air for an oil cooler in front of the left front tire - the idea being not to steal too much air from the radiator. I figured that I didn't want air warmed by an oil cooler to be used to cool my water but I was too cautious in that regard. Dave Anderson had an interesting oil cooler arrangement (
https://www.prevanders.net/europa/oilsystem.html). He isn't specific about how efficient it is though. The plain fact is that I have an oil temp gauge and my oil has never been really hot. I have an oil thermostat and I'm sure it's been opened but I don't think it is a common occurrence based on the oil temp readings I see. If I knew what I know now when I built my car, I might not have bothered with an oil cooler. If my car had a lot of track time, I would probably be glad to have one, though.
As for overheating, I've never had a problem with it. I don't do much downtown stop and go traffic driving which would be harder on the cooling system. I really think that is the only time the cooling system is really marginal. I use Red Line's Water Wetter and distilled water (It rarely freezes hard here and the car is in the garage anyway so it never experiences a freeze at all) and I have an aluminum radiator with the highest CFM fan I could find. Other than that, my cooling system is not remarkable.
