This video shows a device that can compare airflow of different air filters. This Air Flow Demonstrator uses electric fans inside an acrylic box to pull air through an air filter raising a ping pong ball enclosed in the air exit tube mounted on top of the unit. In the first phase of the demonstration, the Air Flow Demonstrator is set to the ON position without placing an air filter in the front of the box. The ping pong ball shoots straight to the top of the tube because there is no restriction holding it back.
The second segment of the demonstration is done with a disposable paper air filter installed on the front of the box. When turned on, the ping pong ball does not shoot right to the top of the tube. The restriction of the standard OEM paper filter prevents much of the air from being pulled in by the fans.
In the last stage of the demonstration the paper filter is replaced with a K&N high flow air filter. The K&N air filter allows more air flow into the box pushing the ping pong ball right back to the top of the tube. This demonstrates that the K&N air filter has less restriction than typical disposable OEM paper filters.
It would be interesting to see how different aftermarket air filters compare against each other as well using this device. Also notice how the woman in the video seems to get pretty excited when the ping pong ball gets it up.