Owner's manual

Page 14
Using the F/IC
The F/IC is a very unique product, capable of precise Fuel and Ignition Control.
However, the F/IC, by design, is a “piggyback” engine controller, not a stand-alone
ECU. Because it is a piggyback controller, the F/IC relies heavily on the factory ECU. As
factory ECU’s get more and more complex, it is more difficult to sustain improved
engine performance without the factory ECU “detuning” the engine. Thus, the key to
using the F/IC is to make it work in harmony with the factory ECU.
Tuning Tips
 Tuning tips and F/IC informational videos can be viewed on AEM’s website:
http://www.aempower.com/ViewCategory.aspx?CategoryID=327. The videos will
help you become familiar with all of the powerful features the F/IC has to offer.
They contain a wealth of useful information to help you extract the maximum
from your F/IC unit.
 Tune the F/IC so the factory’s ECU’s closed-loop fuel trims are as close to zero
as possible using the fuel maps. Change the factory ECU’s closed loop target air-
fuel ratio (AFR) using the O2 table. Most factory ECU’s can sense extra fuel and
will promptly adjust the fuel trims to remove the extra fuel. For easy reference,
fuel trims can be monitored with an OBDII scanner or equivalent device. Positive
fuel trims are reduced by adding fuel. Negative fuel trims are reduced by
removing fuel.
 Keep it simple. Many times it is not necessary to use every function of the F/IC
to obtain the desired engine performance. If the desired engine performance can
be achieved by adjusting only two maps, use only the two maps. There is no
benefit to adding fuel in one map and removing it in another.
 Be conservative when making changes. A small step in the wrong direction is
less likely to damage an engine than a large step in the wrong direction.
 Use the Oxygen Sensor functions only when additional closed-loop fuel is
needed.
Absolute Pressure Explained
(Note: The F/IC reads and displays absolute pressure. Please read the
following section before tuning.)
When talking pressure, there are two common ways pressure is represented,
Gauge, and Absolute, Gauge being by far the more common way. Take a tire for
example, if the measuring gauge says 50 psi, we say the tire has 50 psi of air in it.
However, that is not 100% correct. The tire actually has air at 50 psi above atmospheric
pressure, which is known as psi gauge (psi
g
). The total pressure, or absolute pressure
(psi
a
), is actually 50 psi on the gauge plus the atmospheric pressure. So, the absolute
pressure is the gauge pressure plus the atmospheric pressure. What about boost
gauges? Most boost gauges display gauge pressure both above and below atmospheric
pressure. Pressure above atmospheric pressure is commonly referred to as “Boost”
pressure. Pressure below atmospheric is commonly referred to as “Vacuum”. So why
the lesson on absolute pressure? BECAUSE THE F/IC READS AND DISPLAYS
ABSOLUTE PRESSURE!!! For easy reference, the following formulas can be used to
determine “Boost” and “Vacuum” pressures. Atmospheric pressure can be determined
by reading the F/IC pressure with the key on and the engine off.
P
(boost)
= P
(F/IC) –
P
(atmospheric)
P
(vacuum)
= P
(atmospheric)
– P
(F/IC)