Trivial mod component that extends the default city maximum cultural radius from 5 to 8, by changing the default value of MAXIMUM_ACQUIRE_PLOT_DISTANCE global define. With this change, your city can now acquire (by culture expansion) tiles at 8 tiles of distance from your city. It doesn't change anything else: the default city maximum purchase radius remains at 3 tiles and the default minimum distance between cities in the same mass of land remains at 4 tiles.
I think people who likes to play OCC could greatly enjoy it. You can easily set MAXIMUM_ACQUIRE_PLOT_DISTANCE to other reasonable value if you want. I have decided to leave it at 8 because it's the maxium radius you can see in City View. There, you can also see the next tile that would be acquired in the next cultural expansion of the city, even with values greater than the default. I've tested even with a value of 10, and it seems to work properly (although with this value you can't see the next tile expansion on some cases, due to the limits of the viewable area in City View). I suppose a very long value could lead to a memory overflow or only work at a hard cap established in the DLL source code (I haven't investigated it). You can easily increase the new value of 8 by modifying it in the file "GlobalExtCityRad.xml" in the mod folder.
The related forum thread is: http://forums.civfanatics.com/showthread.php?t=514033
Civ 5 Extended City Radius 2016-10-05
Civ 5 Extended City Radius