AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 19)

Page 19 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
A high quality over-molded termination is included for USB communications. Plug one end of a
standard USB extension cable (included) into the harness connector and the other end into an
open USB port on the PC. Communications is possible only when the EMS is powered up.
CAN Connector
CAN Connector
A compact pre-terminated connector is included for use with AEM CAN enabled devices.
Injectors
Injector Basics
A fuel injector is a valve that can be opened and closed very quickly. To open the valve, current
must flow through a solenoid contained in the upper part of the injector assembly. The EMS-4
triggers the injector by providing a ground path to the negative terminal. Fused power is
provided to the other terminal from the harness.
WARNING! – The EMS-4 is compatible with high impedance injectors only. For direct
drive operation, injector coil resistance must be greater than 8 ohms. Low impedance
injectors can be used if a suitable ballast resistor box or Peak and Hold Driver module is
used such as AEM P/N 30-2710.
To determine the size of the injectors, the total engine power must be estimated or known. The
fuel pump calculations and BSFC information mentioned in the Fuel Pump Sizing section on
page 135 provides a good understanding of the fuel requirements for an engine. The following
equation will allow you to determine the requirements of your injectors: