OP, rather than taking direct measurements, or getting folks on the forums to do the same, have you tried searching for existing automotive research papers that already have such data that you can reference instead? I'm thinking papers published by SAE (Society of Automotive Engineers), ASME (American Society of Mechanical Engineers), etc...
I did a quick Google for the term "intercooler performance papers" and this is the first one that came up. Looks like it has exactly the kind of baseline data you're looking for (Temp in vs. Temp out). There may be more relevant data out there, but I don't have the time to dig further
http://www.academia.edu/3806153/DESI...AN_INTERCOOLER