GFB Respons TMS Valve (part T9001) - Manual (Page 3)

Typically, most Subaru engines will allow 100% atmosphere venting with no problems. However, some
combinations of modifications can 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. 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
(figure 4). 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 4). Do not set the screw more than 3mm above
the head.
•
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 – because of the electronic throttle, you will need a helper
to do this whilst you watch the piston. 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”. 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 and then rise again, tighten the spring 1-2 turns
•
If a loud flutter is heard when lifting off sharply after accelerating hard above 3500RPM,
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