1999 f355 bypass valve

The bypass valve is a butterfly style valve, it rotates 90 degrees to fully open and is actuated by vacuum. The OEM bypass valve is normally closed and require a vacuum source to open, you’d have to either:
A: have a constant vacuum source
B: remove the bypass valve assembly, remove the lever arm, weld the metal plate in place
C: remove the butterfly valve inside the assembly
D: get a capristo valve which is normally open, it uses a different actuator that works in reverse. Open at low vacuum, closes at mid vacuum, open at high vacuum

Picture of the capristo attached
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I don’t know why you’d want to do this, but good luck!


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There are two more options,
1. You can simply use a copper wire to hold the valve in the open position externally.
2. Buy a capristo or Forza exhaust valve controller.
I have the capristo one on my car, it allows me to either leave the valve open all the time, or leave it in the factory setup
I absolutely love it

 

No. I did this for a while, basically loop the copper wire from the actuator arm up to the bracket when the valve is in the open position.
Do note, you will get a check engine light if you have a thermocoupler after the bypass. You can avoid this just by removing that thermocoupler and zip tieing it out of the way and capping the hole

 

You should be able to do this relatively easy by re-routing the vacuum tubes near the bypass solenoid (as long as they are in good condition). You may need a "T" piece to join up the tubes.

I've been told that manually manipulating the linkages on vacuum operated valves can damage the diaphragm in the vacuum capsule if you go beyond its normal range. You should be ok if the valve is currently set up properly.

Some folks have had varying degrees of success with the Check Engine Light after doing this modification.

 

If you decided to use vacuum (instead of lockwire on your valve)....

Just attach pipe 35 to pipe 11 or to the "T" piece directly.
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