Its probably trying to pull down a map update or something. depending on what router you have, and your IT competency, you could log into your router and turn on any QoS (quality of service) features it has, or, look for options to limit bandwith on a specific IP and limit the bandwith of your car.
I dont know if map updates notify you like firmware updates, but if I had limited internet, the QoS or bandwith limitation on the car IP would be what I would do.