GFB G-Force2 - Manual (Page 9)

The Sensitivity setting controls a closed-loop correction factor that attempts to correct any difference between the
actual boost and the target boost pressure. This is useful on a turbo that tends to drop boost pressure as RPM
rises (boost taper), and can also help pull boost pressure up to the target when it is rising very slowly (such as in a
very high gear).
NOTE: the sensitivty setting requires a target “peak” boost to be set up in duty cycle. If you adjust duty
cycle without performing a boost run, the target boost will be 0 and sensitivity will not perform closed-loop
corrections.
Boost taper is common on small factory turbos, because they are typically sized for mid-range response rather than
top end power, and as such they tend to “run out of puff” at high RPM.
The Sensitivity feature can help curb the boost drop-off. It is adjustable between 0-100, where 0 results in no
closed-loop correction at all, and 100 is the strongest correction possible.
If the setting is too high, the boost pressure might start getting unstable, so this is another setting that should be
tested experimentally to find what works best for your turbo.
If you notice that boost pressure falls away at high RPM and you want to try to correct this behaviour, follow the
steps below:
1.
Make sure duty cycle has first been adjusted and peak boost set, as per page 7. It is not necessary to set
gain for sensitivity to work, but if you do plan to use gain you should set it before adjusting sensitivity.
2. Select the boost preset that you want to adjust (see page 6), then navigate to the “Sensitivity” menu (tap
“MENU” three times from Running Mode) – the screen will scroll “SEnS”, followed by the current Sensitivity
setting (default is 0).
3. Drive the car in such a way that the boost pressure falls off at high RPM, and take note of the highest
pressure drop and the RPM, e.g. boost falls from 18psi at 5000RPM to 15psi by 7000RPM.
4. Now increase the Sensitivity setting using the up/down buttons, then drive the car again (using the same
method as above to ensure consistency).
5. Note how the boost taper rate changes, and continue to adjust the Sensitivity setting to achieve the desired
result. If you notice that boost starts to become unstable (i.e. oscillates or goes up and down rapidly),
reduce the sensitivity setting until stable boost pressure is achieved. It may not always be possible to
completely eliminate boost taper depending on how severe it is, but this setting will at least ensure that
everything the turbo system is capable of is being delivered.
6. When done, tap “MENU” to move on to the next menu item, or hold “MENU” to exit. In either case, the
Sensitivity setting will be saved to the boost preset that you are currently in.
7.
Repeat this procedure for any other boost memories you may wish to set up.
NOTE: the Sensitivity function is automatically turned off when making boost pressure adjustments (in Duty Cycle)
so that you can record the true peak boost, however it will be reactivated when you return to Running Mode.
There are limits to what the G-Force II can do with the turbo and wastegate – if the duty cycle setting is already
quite high, there is not much adjustment left for the controller to make if boost drops off – once the closed-loop
corrections reach 100% duty cycle, there's nothing more the controller can do as this is the turbo system's limit.
Because of this, it may not always be possible to completely eliminate boost taper, although it should be able to be
reduced at the very least. The only solution (in this case) to hold more boost is a larger turbo, different wastegate
spring, or both.
9 - setting the boost pressure
Sensitivity