What exactly does the heat shield do?

The Injen Aluminum Heat Shield will block off high-temperature air that normally gets sucked into your induction system due to the placement of your air filter. Keep the hot air out and the cold air coming in!
The Injen intake filter heat shield helps protect against heat soak as well as water that may splash over the filter. It will also keep the filter clean between re-charges for a longer period of time. Put this together with the looks and you have one great product.