GFB DV+ (part T9352) - Manual (Page 4)

What to expect from your DV+
The DV+ is designed to offer three key improvements over the OE diverter:
Longevity:
The DV+ will outlast any version of the factory diverter. If you’ve ever replaced a factory diverter, chances are it
won’t be your last. Fitting a DV+ is good insurance and pays for itself after one or two factory diverter replacements.
Boost holding:
The diaphragm type OE diverter valves typically seal well, until they begin to fail - which is not uncommon and
almost assured on a tuned engine. The common failures of these OE valves include diaphragm punctures or tears,
piston seals detaching, or the thin plastic shroud around the diaphragm itself can become brittle and crack, which
can send pieces of plastic through the turbo.
The DV+ will seal properly even up to 35psi, ensuring all your hard-earned boost gets to the engine. Of course, the
peak boost pressure will depend entirely on the condition of the factory diverter you replace – if the factory valve is
not (yet) leaking, then there will be no increase in boost pressure from fitting a DV+.
However, if your factory valve is leaking even a small amount, fitting a DV+ may show the same peak boost, but with
an improvement in the amount of boost held to redline. This is because a small leak is easily overcome by the turbo
in the mid-range, but at higher RPM as the turbo runs out of flow, a small leak can lead to a more noticeable drop in
boost pressure. In this instance, the DV+ will result in less boost drop-off at high RPM.
And if your factory valve is leaking significantly (e.g. torn diaphragm), fitting the DV+ will result in higher peak boost
pressure, as well as less drop-off at high RPM.
Throttle response:
When using the DV+ with the main spring installed, it will preserve as much boost pressure as possible when the
throttle is lifted. This means that when you lift off to shift, or when you balance the car with the throttle mid-corner
(using slight on-off-on throttle modulation), the DV+ can help recover boost faster.
What the DV+ can’t do however, is create more boost, or cause the turbo to spool faster. Quite simply, whatever
boost the turbo makes, the DV+ will deliver to the engine, and it will also preserve as much boost pressure as
possible during a brief throttle lift-off, which is where the faster boost recovery comes from. If there is no boost to
preserve, or if boost still drops off at high RPM, that is simply highlighting the limitations of the turbo.
Notes on using the DV+
On some cars, the different operating method of the DV+ that is used to improve throttle response can result in
different sounds from the intake at low RPM. This is no cause for alarm, and does not indicate a faulty valve.
This condition is harmless to the engine and turbo, but if you find the noise objectionable, simply remove the main
spring (the left-most spring in the exploded diagram opposite) from the DV+. This will cause the DV+ to operate like
the factory diverter, which will forfeit the benefit of improved throttle response and boost recovery, but it will still
offer boost holding and longevity benefits over the factory diverter.