GFB T9503 User Manual

Deceptor Pro II Blow-off Valve

Installation Instructions

P.O. Box 1017 Riverwood NSW 2210

Ph: [phone] Fax: [phone]

Website: www.gfb.com.au Email: [e-mail]

Fitting Instructions for GFB Deceptor Pro II (part # T9503)

(fits MY01–07 WRX, MY01-on STi, and MY05-08 Forester XT)

Included in the T9503 kit:

 Deceptor Pro II blow-off valve
 Electronic in-car volume controller

 Double sided mounting tape
 2 x stainless steel mounting bolts

Thank you for purchasing the GFB Deceptor Pro II blow off valve. We highly recommend that you familiarize
yourself with the operation and adjustments of the Deceptor Pro II before installing it.

Installing and wiring the in-car volume controller

1) Test the unit before installation by connecting the Deceptor Pro II’s plug to the in-car controller. Connect the

red wire to the positive terminal of your car’s battery or a 12V source. Connect the black wire to the negative

terminal. Upon initial power-up, the unit will perform an open/close cycle before reverting to the position
indicated on the controller dial. By turning the dial and watching through one of the valve’s venting outlets,
you will see the inner sleeve move to open or close each of the venting ports alternately, which is how the
venting volume is adjusted.

WARNING: Do not manually rotate the noise adjustment, always apply power and use the controller
to change the venting bias. When testing your Deceptor Pro II, DO NOT put fingers or foreign
objects through the trumpet or plumb back ports. Doing so may result in personal injury or damage
to the blow-off valve.

2) Find a suitable location on or around the dashboard, steering column or instrument binnacle for your in-car

volume controller. Clean both mating surfaces with Methylated Spirits or similar cleaner and secure the
controller using the supplied double-sided tape. Press hard and hold the unit for about 30 seconds, and note
that it takes up to 24 hours for the tape to develop a strong bond.

3) Using a multi-meter or voltmeter, find a suitable power wire that reads 12V only when the ignition is turned

on. Solder the end of the volume controller positive (red) wire to the 12V source. It is possible to use a wire
tap or crimp instead, but soldering is the most reliable joint. Make sure to insulate the joint properly.

4) Find a suitable bolt on the body/chassis and connect the unit’s ground (black) wire to it.

5) At this point you should plug the Deceptor Pro II back into the in-car volume controller, and test its operation

again to ensure the electrical connections are good. Make sure the unit powers on and off with the ignition.

6) Unplug the Deceptor Pro II and pass the controller’s extension lead through the firewall into the engine bay.

Often there is an existing grommet that can be used for this purpose. In any case, it is important to ensure that
the lead is protected where it passes through the firewall to prevent wear or damage.

Installing the Deceptor Pro II blow-off valve

On Impreza models without an electronic throttle, it is necessary to move the intercooler to gain access to the hose
clamp under the factory valve. It does not need to be removed completely; it just needs to slide back far enough to
reach under. These instructions take you through it step-by-step.

For Impreza models with an electronic throttle and also Forester XT models, it is usually possible to access the clamp
without shifting the intercooler. In this case, simply ignore the steps 1, 3, 4 & 5.

1) Pull the hoses from aluminium tubes that run

across the front of the intercooler (there are
two on the left and 1 on the right. See figure
1, step 1).

2) Using a 12mm spanner (wrench), undo the

bolts that hold the factory bypass valve and
remove, leaving it supported by the hose.
Take care not to drop the bolts or gasket
from behind the valve (figure 1, step 2).

3) On the short hose section between the

intercooler and throttle body, loosen the
hose clamp closest to the intercooler.
Loosen the clamp holding the hose onto the
outlet of the turbo (figure 1, step 3)

Figure 1

4) Undo and remove the two mounting bolts (again

using the 12mm spanner) that hold the intercooler
in place (figure 1, step 4).

5) Carefully slide the intercooler back just enough to

access the hose clamp under the valve (figure 2).
Take care when handling the intercooler since the
cooling fins are very fragile, and also take care not
to bend the plastic hose from the turbo too much.

6) Take note of the position of factory valve and then

use pliers to open the recirculation hose clamp
(figure 2). Remove the valve from the recirculation
hose and vacuum hose.
Figure 2

7) The Deceptor Pro II comes supplied with a new gasket that must

be used in place of the existing factory gasket. If the factory
gasket is stuck to the intercooler, use a knife blade or similar to
free one end, then carefully peel it off. Make sure there is a clean,
flat surface left for the o-ring to seal on, remove any remnants of
the gasket before proceeding.

8) Now unscrew and remove the return nozzle from the factory

valve. Fit the return nozzle to the outlet of the Deceptor Pro II as
shown in figure 3, using the screws and the o-ring from the
factory valve.
Figure 3

9) Remove the trumpet by unscrewing it in an anti-

clockwise direction from the Deceptor Pro II to allow
the mounting bolt to be inserted into the hole (see
figure 3). Once the valve has been bolted to the
intercooler you can replace the trumpet.

10) Push the return nozzle into the recirc hose in the same

way as the factory valve, and replace the hose clamp
(figure 4).

Figure 4 (earlier version Deceptor Pro shown)

11) Slide the intercooler back into position, then bolt the

valve onto the intercooler using the supplied gasket
and stainless steel screws, and tighten them with a
5mm Allen/hex key. Push the vacuum hose onto the
brass nipple, and then replace the trumpet (figure 5).

Don’t forget to replace the intercooler mounting bolts

and tighten the intercooler hose clamps.

12) Connect the Deceptor Pro II’s lead to the plug from the

controller, ensuring that the whole cable is secured in
the engine bay away from direct heat sources or
moving parts.

13) Bundle any excess cable under the dash and cable tie it

securely. Figure 5 (earlier version Deceptor Pro shown)

Adjusting the spring pre-load

Contrary to popular belief, the spring pre-load DOES NOT need to be adjusted to suit different boost levels. Unlike
other valve types on the market, the Deceptor Pro II will stay shut under full throttle conditions regardless of
boost pressure or spring pre-load.

The spring pre-load affects how easily the valve opens when you
lift off 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.

Note that there is no substitute for experimentation with the
spring setting, because different cars in different climates and
with different mods will unsurprisingly respond differently. Do
NOT be afraid to experiment to find the optimum setting, you

can’t hurt the engine or turbo by doing so. The guide below will

walk you through the steps involved.

The screw in the centre of the head is the spring pre-load adjuster
(figure 6), and the direction of adjustment is labelled (+ direction
increases spring pre-load). 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 (figure

6). Do not set the screw more than 3mm above the head (an o-ring fitted to the screw head will become visible if the
screw is wound out more than 3mm – the o-ring must remain below the head of the valve).

 Set the spring to the softest setting, and set the volume control to at least 50% atmosphere venting so you can

see the piston through the trumpet

 Start the car and let it warm up to normal operating temperature. Make sure the A/C is off
 Look at the piston through the trumpet. If it is hovering open, wind the adjustment screw in the “+” direction

until the piston closes fully. If it is already closed, proceed to the next step

 Give the engine a good hard rev and snap the throttle shut quickly. The piston should lift and vent, then close

slowly and smoothly. The harder you stab the throttle, the further the piston will open (note: it will only open
fully when driving, as the turbo does not generate boost until the engine is under load). WARNING: Keep
your face away from the trumpet opening when revving the engine. View the piston from an angle away from
the blast of air

 If the piston stays open too long, and is not closed when the revs drop back to idle, the engine will “stumble”,

or the revs will dip below idle. If this happens, wind the adjustment screw in the “+” direction one turn at a
time until the engine returns smoothly to idle after revving

 For the final fine-tune, take the car for a drive. Watch the tacho as you pull up to a stop - if the revs dip below

idle, tighten the spring 1-2 turns

 If a loud flutter is heard when lifting off sharply from full boost, wind the adjustment screw in the “-“

direction one turn at a time until the noise disappears. Note that it is not uncommon to hear a slight fluttering
at low RPM under certain conditions. This is a result of the different way in which this valve operates
compared to the factory unit, and is perfectly normal

A video example of setting up the spring pre-load can be seen at:

http://www.youtube.com/watch?v=iqQR5WUF9lc

NOTE: There is usually a range of around 4-5 turns within which your valve will operate properly, and if it is outside
this range it will be immediately noticeable in the symptoms described above. If you notice none of the symptoms
mentioned above, then simply leave it where it is.

Using the In-Car Controller

When powered up the volume dial rim will glow red, and will brighten for easy reading when you make an
adjustment, then automatically dim 3 seconds later to reduce unnecessary glare. The position of the dial is directly
proportional the venting bias - turning the dial fully anti-clockwise sets the valve to 100% recirc, fully clockwise
results in 100% atmosphere venting, and any proportion is possible between these limits.

The controller also features a program button on the rear of the casing. This can be used to limit the range of the
atmosphere-venting bias of the Deceptor Pro II. For example, if you prefer that the maximum atmosphere venting bias
is 50%, you can program the controller so that full travel on the dial gives you only 50% movement at the valve. This
is particularly useful on cars that through experimentation, find that full atmosphere venting does not agree with them.

To use this feature, set the dial in a position that you want as your maximum atmosphere-venting limit, then press and
hold the program button until the dial flashes. The unit will now record this position as the maximum atmosphere­venting limit. Now when you turn the dial fully clockwise, the Deceptor Pro II will only open as far as the point
which you have just set. For example, if you pushed the button with the dial set in the middle (50% atmosphere
venting), full travel of the dial will now move the valve from full recirc to 50% atmosphere-venting only.

Every time the button is pushed, the position of the dial will determine the maximum venting bias of your Deceptor
Pro. So to re-set the controller to allow the full range again, simply turn the dial fully clockwise and push the button.

Maintenance

All GFB valves are designed to be as maintenance free as possible. In most cars the small amount of crankcase and
rocker-cover blow-by oil that is directed into the intake system is enough to keep the piston well lubricated. However,
in some cases oil deposits or dirt can dry out and create a build-up on the piston that causes erratic operation or
sticking. If you notice a grey film on the piston or erratic venting behavior, it is a good idea to clean the valve.

This is best done with the valve removed from the car. Flush out the piston with a penetrating spray such as WD40,
whilst working the piston up and down. Using a rag, wipe off as much of the grime and build-up as possible. Re­lubricate the valve by applying a small amount of engine oil to the piston through the side outlets and the underside of
the valve, and working the piston up and down by hand. It is a good idea to keep the trumpet area clean and free from
oil, as it attracts dirt which can result in damage to the piston.

Customer Support

GFB’s engineers are always available to help with any enquiries or issues you may have with the installation or use of

your GFB products. Simply email [e-mail] or phone:

Within Australia: 02 9534 0099

International: [phone]

This product is intended for racing use only, and it is the owner’s responsibility to be aware of the legalities

of fitting this product in his or her state/territory regarding noise, emissions and vehicle modifications.

GFB products are engineered for best performance, however incorrect use or modification of factory
systems may cause damage to or reduce the longevity of the engine/drivetrain components.

GFB recommends that only qualified motor engineers fit this product. Warranty is for the period of one
year from the date of purchase and is limited only to the repair or replacement of GFB products provided
they are used as intended and in accordance with all appropriate warnings and limitations. No other
warranty is expressed or implied.

Go Fast Bits

P.O. Box 1017 Riverwood NSW 2210

Ph: [phone] Fax: [phone]

Website: www.gfb.com.au Email: [e-mail]