GFB Deceptor Pro II (part T9500) - Manual (Page 2)

Installing the blow-off valve
Covered vehicles:

WRX/STi MY99-00

Forester GT MY98-02

Forester XT MY03-04
The Deceptor Pro II (part # T9500) is designed to be a direct factory replacement, and
installation is as simple as removing the factory valve and replacing with the Deceptor Pro II as
follows:
1)
Loosen the hose clamps from the recirc and vacuum hoses on the existing factory bypass
valve, then pull the hoses free.
2)
Using a 12mm socket, remove the two bolts holding the factory bypass valve to the
intercooler, and remove the valve entirely.
3)
Making sure the factory gasket is still in place, re-install the two bolts and screw them in
about 3 turns each. The Deceptor Pro II can now be installed by inserting the lower slot on
the flange onto the lower bolt, then rotate the valve so the upper slot fits onto the upper
bolt.
4)
Tighten both bolts, then fit the recirc and vacuum hoses onto the Deceptor Pro II and
replace the hose clamps.
5)
Connect the servo motor plug to the wiring loom from the controller, and make sure the
cable is securely routed through the engine bay away from exhaust or turbo parts.
Spring Adjustment
Contrary to popular belief, the spring pre-load DOES NOT need to be adjusted to suit different
boost levels. The valve will stay shut under full throttle conditions regardless of boost pressure or
spring pre-load.
Rather, the spring pre-load affects how easily the valve opens when you lift the throttle, and how
long it stays open when it vents. Adjusting the spring is a simple matter of ensuring the valve opens
enough to release the air, but not long enough to cause idling problems. The guide below will walk
you through the steps involved.
The screw in the centre of the head is the spring
adjuster (shown opposite). Use the supplied 5mm
hex key for this screw.
The softest spring setting is achieved when the top of
the adjustment screw is 3mm above the head of the
valve. Do not set the screw more than 3mm above
the head.
Note that the spring adjusting screw may be obscured by the coil pack when installed, so if
adjustments need to be made it is easiest to simply loosen the two valve mounting bolts only enough
to rotate the valve up high enough to access the spring adjustment screw, rather than remove the
valve entirely.