|
Tuning your car with an AFC? -What is the Apex AFC? The SAFC
is a computer that modifies the vehicle’s speed density or
air flow sensor (Manifold Absolute Pressure, Mass Air Flow)
signal to the ECU of the car. This is really useful because
it can "lie" to the car’s ECU about how much air it is
getting (we will come back to this soon). Accordingly, the
ECU will give more or less fuel to the engine, thus helping
you tune. Added use of the AFC comes from the fact that you
can play with the settings throughout the RPM range and
different throttle positions. The ECU needs to calculate the
amount of fuel to shoot into the motor. In order to know how
much gasoline it needs to inject, it needs to know how much
air is coming in, and what the target air to fuel ratio (A/F
ratio) is at that point in time. This is the job of the air
metering devices, and some of the code in the ECU, which
interprets the information from these devices. The reasons
why this should be left to a professional are listed below.
If you feel comfortable continuing the install and tuning,
and are willing to risk blowing up the car, by all means,
please, continue.
As mentioned above, there are many possibilities to doing
this the WRONG way. For one, you are actually lying to your
ECU about reported air flow volume, fooling your ECU into
delivering shorter/longer fuel injector pulses to compensate
for larger injectors. Lie to it incorrectly and you will
have too short an injector pulse resulting in a lean
condition possibly leading to detonation. A leaner fuel
mixture will detonate easier, and when the engine is hot, it
will detonate just because of higher compression near the
top of the compression stroke, even without spark telling it
to. If the air/fuel mixture detonates, peak cylinder
pressures will occur before it’s optimum time, possibly
forcing the piston back down again backwards against the
force of the other pistons. This is called detonation or
pre-detonation or commonly known as engine knock. It can
melt holes in pistons, destroy piston rings, bend connecting
rods break crankshafts etc etc. With this in mind, proceed
with caution. This is just one reason they say you should
have it installed.
A very important piece of information is not what the AFC
controls, but what it inadvertently controls. You can adjust
fuel, as noted above, but as a side affect ignition timing
is changed. Now, the ignition timing change, depends on the
amount of fuel correction made with the AFC. Worst case
scenario would be leaning your car out too much while
advancing ignition timing. This alone has possibly claimed
the lives of more 4G63s than crank-walk because of
inexperienced customers reading incorrect information on
forums or listening to friends. The timing map in the ECU is
set up as such: the ECU looks at the engine speed and the
airflow or pressure, and then finds the point on the timing
map. The timing map is set up like a spreadsheet, with the
columns representing either engine speed or airflow, and the
rows representing the other. The tendency of the timing map
is that lower airflow (less load on the motor) gets more
timing advance. The effect of the AFC is that if the fuel
correction is reduced the amount of airflow that the ECU
sees will accordingly. The ignition MAP listed below can
give you a visual representation of what happens to your
ignition timing as you "lean" out your fuel mixture using an
AFC. |
