Race Cover Instructions


Threaded inlet

Bullseye Powers 4th Generation patented tunable compressor cover has unique features that set it apart from any other cover on the market. Following these simple guidelines will ensure your compressor cover performs optimally and has a long service life. The compressor cover features a threaded inlet bell, which allows you to tune the map groove width for the best powerband for your engine combination. Each full turn of the inlet bell is 1/16 inch. When looking into the inlet bell, clockwise rotation closes the groove and counterclockwise rotation opens the groove. The map groove is tunable from 0 to 6 full turns. The inlet bell should always spin freely. Never apply excessive force. Do not force closed, or additional force may be required to separate the pair this can damage the cover. Due to exact machining tolerances it will seat itself shut tightly. DO NOT REMOVE THE BELL COMPLETELY! THE INLET BELL CAN EASILY GO BACK IN CROOKED 1 OR 2 TURNS AND GET CROSS THREADED. SERIOUS DAMAGE TO THE THREADS CAN OCCUR DUE TO INLET BELL REMOVAL.  

Set Screws

The 3 set screws are nylon tipped, care must be taken when locking down the inlet bell. Screws must be torqued to 15-17 inch pounds using Non-permanent (blue) thread locker. We suggest checking the screws for tightness periodically, IE: After the first few heat cycles, tire shake or a bumpy drive. Always make sure you tighten the locking screws evenly as not to force the inlet to one side of the compressor cover to avoid the compressor wheel from possible touching down.

Threaded Outlet

When using the optional screw on V-Band flange, ensure the PTFE O-ring is located before installation. Screw on and snug the flange hand tight. Do not apply excessive force. In applications where the charge pipe is not rigid and could rotate during use, you may use a small removable spot weld to secure the flange.  

Tuning tips

Once a baseline is established or after you make 3 or 4 consistent runs or pulls, start with the map groove closed. Make adjustments in 2 full turn increments unless surge is present or your really after fine tuning improvements then record performance at i full turn increments. Open the inlet bell another full turn or 1/8th inch and repeat. Once an optimal number of turns is found, the map groove width can be further tuned as precisely as desired. A permanent marker can be used to measure rotation.Good luck, have fun and be safe!