GFB T9003 User Manual

Installation Instructions for GFB Respons T9003

Applicable vehicles:

• WRX MY01-07

• STi MY02-on

• Forester XT MY05-08

NOTE: the flange on the Respons may appear to be loose, but this is normal and does not
affect its ability to seal properly – once installed the valve will be clamped firmly.

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 off the hoses from aluminium

tubes that run across the front of the
intercooler (2 on the left and 1 on the
right hand side. See figure 1, step 1).

2) Using a 12mm socket or wrench, undo

the bolts that hold the factory blow-off
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 hose between the intercooler

and throttle body, loosen the hose
clamp closest to the intercooler, and 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

with the 12mm socket or wrench) that hold the
intercooler in place (figure 1, step 4).

5) Carefully slide the intercooler back just enough

to access the hose clamp on the BOV (figure 2).
Take care when handling the intercooler since
the cooling fins are very fragile, and also take
care not to bend the 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 and vacuum hoses.
Figure 2

7) On the factory valve, remove the recirc elbow by

unscrewing the two Phillips-head screws holding it
on. Fit the recirc elbow to the outlet of the Respons
(figure 3) using the factory screws and o-ring.

8) At this point you must unscrew the trumpet from the

Respons to allow the mounting bolt to be inserted
into the flange hole (figure 3).

9) If the factory gasket is stuck to the intercooler at this

point, it should be removed. Scraping may be
required to remove all gasket material if it does not
come off cleanly. Take care not to drop any gasket
material into the intercooler.

10) Push the elbow into the recirc hose in the

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

11) Bolt the valve onto the intercooler using

the supplied stainless steel bolts and
replace the intercooler.

12) Push the vacuum hose onto the nipple on

the top of the valve. Screw the trumpet
back in place and do a final check to make
sure all bolts and clamps are tight.

Adjusting the Noise

The unique patented venting bias adjustment
feature on the GFB Respons lets you vary the
amount of air vented to atmosphere or recirc,
thereby changing the volume of the sound.

Turning the venting bias adjuster (figure 5)
clockwise will open up the trumpet outlet more,
making the valve louder, whilst anti-clockwise
will open up more of the recirc outlet for quiet
operation.

Turning the adjustment fully anti-clockwise will
close off the trumpet completely, and the valve will operate like a factory bypass. Conversely,
turning it fully clockwise will make it vent 100% to atmosphere, which is the loudest setting.

Typically, most Subaru engines will allow 100% atmosphere venting with no problems provided the
spring pre-load is set correctly (see below). However, some combinations of engine modifications
may result in backfiring when the valve vents to atmosphere, in which case the solution is simply to
dial back the amount of air vented to atmosphere until the problem is resolved – this is one of the
key benefits of the venting bias adjustment feature.

Do not be afraid to experiment with the spring and noise settings, no harm will come to the engine
if wrong setting is used.

Spring Adjustment

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 Respons 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 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 (figure 6), and the direction of adjustment
is labeled (+ 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

move the noise adjusting ring 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. The piston should lift slightly 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

Maintenance

The GFB Respons is designed to be as maintenance-free as possible. Unlike some other brands on
the market, frequent replacement of seals in order to keep the Respons in top working order is NOT
required.

The only maintenance that may be required is the occasional cleaning of carbon deposits on the
Respons’ piston that result from the oil vapour in the engine’s inlet tract. This varies from car to
car, and on some cleaning may never be required, whilst others may need to be cleaned on a regular
basis. It is easy to determine if the valve needs cleaning by visual inspection of the piston for black
carbon build-up, or if you notice the sound of the valve changing over time (e.g. slow response
time, intermittent operation).

To disassemble the Respons, put a rag under the valve to catch any parts that may drop. Remove
the four screws holding on the cap (use a 3mm metric hex key), taking care as the spring will push
upwards on the cap with approximately 5kg of force. Remove the spring and the brass piston, and
wipe any grime from the inside of the valve and the piston with a rag. Apply normal engine oil to
the piston and the inside of the bore, and re-assemble.

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/drive-train
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.