What is a boost bypass valve?

The bypass valve is integrated in the supercharging system. When low engine power is required, the bypass allows air to enter the engine without passing through the supercharger. The supercharger bypass valve operates in the following manner:
  • Under normal engine operating condition vacuum is supplied to the bypass valve. The valve opens, diverting excess airflow back into the air plenum. This prevents the supercharger from “cavitating.”
    1. Cavitating causes reduced performance, increased temperature, and poor fuel economy.
  • At high engine demands, vacuum is removed from the bypass valve causing it to close. This directs all airflow from the supercharger to the intake manifold.
  • The supercharger boost (SCB) solenoid is used to control intake manifold vacuum to the vacuum bypass actuator. The PCM transmits an output signal to the SCB solenoid, which activates the solenoid to bypass vacuum when the engine is under maximum boost, reducing the boost pressure by up to 3 PSI.
  • Supercharger airflow diagram:
Purpose of a "Boost Bypass Modification"

The purpose of a "Boost Bypass Modification" is to supply continuous boost from your supercharger when engine is under maximum boost limits set by the factory. When acceleration exceeds factory limits (8 psi).

With our boost bypass modification, you will now be able to keep your boost at the maximum level when under WOT usage. The term “boost bypass” is a bit misleading by all those dealers advertising this kit for a price. Its true name should be, WOT bypass eliminator kit . . . This modification does not effect normal engine operation and is designed for modifying boost bypass at WOT only. (WOT= wide open throttle)


Below are the easy to follow instructions detailing how to maximize your boost performance on your Ford supercharged vehicle. Unlike other companies, RPM will provide these detailed instructions at no cost to you. At RPM Outlet, we do not charge you for knowledge.

found at any auto parts store

image 1

Step 1. Locate the boost bypass actuator solenoid and the boost actuator. It’s on the driver’s side of your supercharger towards the back of the engine.
found at any auto parts store

image 2

Step 2. The boost bypass actuator solenoid has two vacuum lines and a two wire plug right above the lines. Take the vacuum line connected to the top of the solenoid and unplug it.

found at any auto parts store

image 2
found at any auto parts store

image 3
Step 3. Disconnect the vacuum line (red circle) connected to the boost actuator. Step 4. Take the line from step 2 and plug it into the boost actuator (red arrow).

found at any auto parts store

image 4
found at any auto parts store

image 5
Step 5. Now take the line from step 3 and plug it into the boost by-pass actuator solenoid (red arrow). Finished. That all there is to it! We still can’t believe shops are charging for this! This modification is nothing more than bypassing the bypass solenoid. One last thing … you can also switch the rubber boots around for a cleaner looking installation.