AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual - Manual (Page 259)

Tuning Guide 253
© 2014 AEM Performance Electronics
From observing the log, the maximum boost pressure should be the same as the wastegate
spring pressure. Keep in mind that there are other mechanical situations which can change the
outcome. For instance, an improper exhaust manifold (or turbo) wastegate port can create
"boost creep".
From the log, the proper open loop boost control duty cycle% can now be determined by viewing
the MAP and BoostControl channels. It is a good idea to make a boost log sheet. This will
speed up boost control tuning when feedback is used by giving you an idea of the duty cycle that
will achieve each boost level. The chart will be dependent on the mechanics of the turbo system,
including: wastegate spring, turbocharger, exhaust back pressure, etc. See the example below:
After the appropriate duty cycle is found that is necessary to reach the desired boost target, the
boost control feedback can be enabled. To do this, check the Boost Feedback Enable box in
the Boost Wizard. Now enter the boost target in the BoostTarget1 [% ] Table.
Below is an example of boost control on an AWD time attack vehicle (not traction limited) that
doesn't need boost-by-gear (or speed). However, there is an AEM 12-position switch (p/n 30-
2056) installed so the boost can be adjusted on the fly.
Notice that there are also several failsafe strategies that will limit boost if the charge air
temperature is too high (heatsoak) or if the coolant temp is out of range (engine too cold or
overheating). In addition, the boost target mapping for the 12-position switch only allows certain
(higher) boost levels if the Ethanol content is high enough to support the boost. The boost target
is also varied based on throttle position, to allow the driver to use the throttle for linear power
delivery, which makes the car much easier to drive on a road course where part-throttle is
common. To aid in spool, the duty-cycle is increased at lower RPM where the engine cannot
attain full boost, and at lower boost pressures, again to keep the wastegate closed as long as
possible to improve response.
The PID system on the Infinity is extremely fast and you'll notice no Derivative Gain
(BoostGain_Kd) was needed.