Setting The Boost Pressure; Duty Cycle - GFB G-Force III Installation Instructions Manual

duty cycle

STOP
The duty cycle setting controls the peak boost pressure, and is adjustable from 10-100%, where 10 represents the
lowest possible boost pressure your turbo system is capable of running (commonly referred to as "base" or "wastegate"
pressure), and 100 represents the highest.
See page 19 for a detailed description of what duty cycle is and how it works.
The duty cycle must be increased carefully and incrementally until you arrive at a setting that results in the target boost
pressure that you want to achieve.
1. Select the boost preset that you want to adjust (see page 7).
2. Tap "SETTINGS" once to navigate to "Duty Cycle" - the screen will scroll "DUtY", followed by the current duty
cycle setting, then "PEAK", followed by the current peak boost recorded for that duty cycle setting. DO NOT
EXIT the menu until the boost setup process is complete.
3. Tap the up/down buttons to adjust the duty cycle setting - it is safest to start at 10 so you can see your car's
minimum boost pressure, and make adjustments from there. NOTE: whenever you make adjustments to the
duty cycle, the "PEAK" boost value will clear to 0.
4. Drive the car to record the peak boost – you will need to ensure that you perform a full throttle run, sweeping
through the engine's peak torque RPM in the highest gear possible/practical to ensure the controller records
the true peak boost - you can do this as many times as you like until you're sure you've recorded the true peak
boost.
5. After lifting off the throttle, the display will alternately show the duty cycle and the peak boost. If the peak boost is
lower than your desired target, increase the duty cycle, then drive the car again (using the same method as
above to ensure consistency) to record the new peak boost.
6. Continue to make adjustments until the peak function displays your desired target boost pressure, and do NOT
make any further duty cycle adjustments or the peak value will reset to 0.
7. Tap "SETTINGS" to move on to GAIN, or hold "SETTINGS" to exit. In either case, the duty cycle setting and
peak boost will be saved to the boost preset that you are currently in. The G-Force III will use these stored
values for the GAIN and SENSITIVITY features. If you do not record a peak boost, the controller will still work,
but GAIN and SENSITIVITY will not be able to make any closed-loop corrections.
8. Repeat this procedure for any other boost presets you may wish to set up.
NOTES:
At 10% duty cycle, the solenoid valve is effectively completely switched off, and above 95% it is effectively fully switched on. It is
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not possible to run less boost than what you can achieve with 10% duty unless you change the wastegate. To run higher boost
pressures than what you can achieve with 95% duty, you must change the turbo or wastegate, or use a 4-port solenoid valve
(available from GFB, part # 3845).
It is not unusual for duty cycle values up to 20% to make little change to the boost pressure, because the solenoid valve response
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is non-linear. That is why the minimum duty cycle in all boost presets is 10%. You may find it necessary to adjust duty as high as
25% before you start to notice an increase in boost pressure - this is completely normal.
The higher the required duty cycle to achieve your target boost, the harder boost is to control - it is more likely that boost will taper
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at high RPM and vary more according to atmospheric conditions with duty cycles in the upper end of the range.
For the reason above, it may be difficult to run high and low boost pressures that are vastly different from each other, for example a
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low boost of 10psi and a high boost of 30psi simply may not be possible with the turbo and wastegate.

8 - setting the boost pressure

BEFORE adjusting duty cycle, it is HIGHLY recommended that you first set
up the OVERBOOST feature (see page 12 for more information).
OVERBOOST is a "global" setting that will turn off the solenoid if boost
pressure exceeds the overboost setting (regardless of the boost preset
currently being used), which is intended to prevent damage to your engine
if the controller is adjusted incorrectly or accidentally.
The factory default setting is 100kPa (1 bar, 14.5psi).