Let's see if I can kill off the WRX style (air to air I/C in the engine bay) first, just moving the standard I/C to the front results in a 10 degree C reduction in inlet air temp and an extra 10 kw. That's on the dyno in a temperature controlled room with 2 fans, one for radiator and one for the I/C, simulating driving at 100 kph.
Often the extra net weight f the water to air I/C is offset by the weight of the much larger air to air I/C plus the larger radiator that they often mandate. Net there is commonly not a lot in it. Plus the advantage of the water to air system is the weight is further back in the chassis, mostly within the wheelbase.
An efficient air to air I/C is going to reduce the inlet air temp to around half of the difference between the compressor outlet temp and the ambient air temp ie; 80 degrees compressor outlet temp + 25 degrees ambient = 55 degrees inlet air temp. A really super efficient air to air I/C with spray might get that down to 40 degrees. Compared to an ice water to air I/C that can get below ambient (until the ice melts).
Personally in hillclimb environment I'd pass on an air to air I/C which does next to nothing while queuing and sitting waiting for the green light and water sprays are frowned on. That especially applies to one in the engine bay suffering from heat soak. Water to air has so many advantages and an esky full of ice will last most of the day.
Cheers
Gary
Golf Mk7.5 R, Volvo S60 Polestar, Skyline R32GTST
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