AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 104)

Page 104 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
The tooth control table has many different functions. The most basic of which is to tell the ECU
what to do when it sees a significant edge on the crank sensor input. The values are plotted
versus “A Tooth”. The A Tooth count will increment on every edge the pattern. In more
complex situations, the table can be used as a translator to convert a complex pattern into a
common evenly spaced pattern of 24 fuel teeth per cycle as shown in the examples above.
A value of “5” in the table tells the ECU to process the significant edge. In other words,
increment the fuel and spark tooth count by 1. The Timing Pattern Basics diagram above
shows what the internal fuel and spark tooth counts would look like for one complete engine
cycle. These are then used as reference values for fuel and ignition phasing settings.
Fuel Phasing and Injector Setup
The fuel and spark outputs from the EMS can be defined many ways. Our example is a 4
cylinder engine with 4 injector outputs and 4 coil outputs. This is an even fire engine meaning
that the angle between each cylinder firing event is the same. A 4 cylinder even fire engine will
have a firing event every 180 degrees.
720 crank degrees total / 4 cylinders = 180 degrees per firing event
A timing pattern with 24 “fuel teeth” such as the one in the examples above means there are 30
crank degrees per “tooth” edge. If an injector must fire every 180 degrees, the outputs must be
set up to fire every 6 “teeth”.
180 degrees per event / 30 degrees per tooth = 6 teeth per firing event