AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual User Manual
Page 295
EFI Components
289
© 2014 AEM Performance Electronics
The MAP sensor provides manifold pressure information to the ECU for calibration based on
MAP vs. RPM. The MAP information is used in both the fuel and ignition Y-axis of their
respective maps. On racing engines that use individual runner manifolds, a TPS based fuel map
can be used while the ignition can be MAP based. This is desirable because the ignition should
always be load based to provide knock free operation.
A MAP sensor reads in absolute pressure, just like the name implies. The amount of pressure
indicated by the sensor depends on the amount of voltage feedback delivered to the ECU. As
the throttle is opened and closed, or boost is built up in the manifold, the sensor reacts to the
changing pressure and outputs a voltage signal to the ECU based on the given pressure.
The MAP sensor has three leads: 5V+ into the MAP sensor, a return to the ECU based upon the
resistance of the MAP sensor, and a ground. A MAP sensor MUST have a hose routed to it from
the inlet manifold in order to read manifold pressure and it MUST receive a constant pressure
signal to it at all times. If the pressure signal fluctuates, the calibration will be adversely affected
because the fuel and ignition values will cycle with the MAP signal.
To avoid varying MAP signals, the pressure line must be connected to the intake plenum. In the
case of individual runner manifolds, TPS-based mapping is best.
If a MAP sensor is used for boost compensation or load sensitive ignition timing, an accumulator
must be used. An accumulator is a common closed container that has a hose from each runner
routed to it. An accumulator dampens the pulsing commonly found in this type of manifold set up,
which will aid in the delivery of a steady MAP signal. Note: A fuel pressure regulator can have its
pressure source routed to an accumulator for the same reasons.
The AEM Infinity has a variety of MAP sensor ranges to suit everything from naturally aspirated
engines, to forced induction engines up to whatever boost can be generated by the turbo or
supercharger(s).