I wasn't that impressed with the induction filter Vans supplied so I did some research on what was available for homebuilts. Reviewing some other builders web pages I found the induction system that was developed by Rod Bower Aviation. The system consists of a round aluminum can that encases the filter. The system also includes a ram air valve that allows the air to bypass the filter with a straight shot to the fuel servo. Since my engine uses a vertical mounted servo, Rod has an elbow that will place the ram air system in the correct position. The ram air kit also includes a modified induction scoop that takes the place of the scoop on the Vans cowling. The scoop can be permanently installed or installed with camlocs. Since I have a 3 blade prop, I decided to go with the camlocs. This will make removing the cowling a lot easier concerning the 3 blade prop.
The ram air valve is closed during the ground operation mode (takeoffs, landings. With the valve closed, air is supplied through the reed valves around the perimeter of the can body. A filter is used during the ground operation. In flight the valve is opened to bypass the filter and provide a direct route of the incoming air to the fuel servo.
The ram air valve is controlled by a push/pull cable. I used a Mac servo and a switch on the console to control the valve. When the valve is opened an annunciator light illuminates to remind you to close the valve for landing.