SECU-3

SECU-3 project logos
SECU-3T revCU6 USB with MAP

SECU-3[1] is an internal combustion engine control unit. It is being developed as an open source project (drawings, schematic diagrams, source code etc. are open and freely available for all). Anyone can take part in the project, and can access all the information without any registrations.

SECU-3 system controls the ignition, fuel injection and various other actuators of the internal combustion engine (ICE) and vehicle. In particular, it is capable of controlling the carburetor choke using a stepper motor (auto choke), thus controlling RPM when engine is warming up. SECU-3 manages AFR on the carburetor engines (similar to AXTEC AFR systems), idle cut-off valve and wide open throttle mode valve in carburetor systems, controls electric fuel pump and gas valves in closed loop mode according to the feedback from the oxygen sensor. The SECU-3 system provides unique opportunities for reassigning the I/O pins of the mainboard for custom uses in engine tuning. It also provides smooth speed control of the engine electric cooling fan. The system includes its own software which allows editing all major settings and fuel and ignition maps in real time (when the engine is running), and switching between 2 or 4 sets of maps. SECU-3 system has many other advanced features (listed below).

Currently, there are five modifications of the unit:

  1. SECU-3. The first version of the unit, developed in 2007, controls ignition, cooling fan and has some other functions. In the latest software releases, the support for this unit had been discontinued. History of the SECU-3 versions with photos could be accessed here
  2. SECU-3T.[2] It can control the ignition and fuel injection. It does not contain built-in power drivers for ignition coils, fuel injectors and idling air control (IAC) valve. External drivers must be used.
  3. SECU-3L.[3] It was designed for ignition control only and it can be considered as a light version of the SECU-3T unit. However, it contains built-in drivers for ignition coils, as well as manifold absolute pressure (MAP) sensor. Regarding the software, it is fully compatible with the SECU-3T unit.
  4. SECU-3 Micro.[4] Very easy-to-use and low-cost ignition controller unit in small plastic enclosure. Has only few inputs and outputs and doesn't contain built-in power drivers for ignition coils. It is the simplest SECU-3 unit.
  5. SECU-3i.[5] Full-featured, complete engine management system in metal enclosure with integrated power drivers (for ignition coils, injectors, IAC actuator etc.), with extended number of I/O and Bluetooth connectivity. The latest development of the system. This unit has double-board design.

The device is developed using the 8-bit AVR microcontroller ATMega644, with 64kB memory (ROM), 4kB random access memory (RAM), and operates at a clock frequency of 20 MHz. It includes analog and digital inputs, separate chip for preprocessing signal from the knock sensor (KS) (except SECU-3 'Lite' and 'Micro' units), a signal conditioner for VR start-pulse sensor (except SECU-3 Micro unit), a signal conditioner for the VR crankshaft position sensor (CKP), the interface with a computer, and the outputs for actuators control.

Structural diagram of the system with SECU-3T unit:

Example of wiring diagram of the SECU-3T unit for controlling of fuel injection
SECU-3 Manager v3.4 - first tab

Structural diagram of the system with SECU-3L unit is shown on the following picture: Structural diagram of the system with SECU-3 Micro unit: Example of wiring diagram of the SECU-3T unit for controlling of simultaneous or semi-sequential fuel injection on the 4-cylinder engine is shown on the picture below. Hi-z injectors and stepper IAC valve are used. On the right side of picture we can see external connector functions which should be remapped to specified values. It is done in the SECU-3 Manager software.

Example of wiring diagram of the SECU-3T unit for controlling of simultaneous or semi-sequential fuel injection. Hi-z injectors, stepper IAC
  1. ^ "Engine Management System SECU-3 / Spark Advance Controller Secu-3".
  2. ^ Shabelnikov, A.A. (2015). "Electronic control unit for internal combustion engine SECU-3". Visnik Nacional'nogo Tehnichnogo Universitetu "HPI". 156 (22). Kharkiv Polytechnic Institute: 90–95.
  3. ^ Shabelnikov, A.A. (2015). "Ignition control system for internal combustion engines SECU-3L (Lite)". BULLETIN OF THE NATIONAL TECHNICAL UNIVERSITY "KHARKIV POLYTECHNIC INSTITUTE" Series: "New Solutions in Modern Technologies". 155 (46 (1155) 2015). Kharkiv Polytechnic Institute: 115–121.
  4. ^ Alexey Shabelnikov (2016). "MICROPROCESSOR CONTROLLED IGNITION SYSTEM SECU-3 MICRO". Materiały Xii Międzynarodowej Naukowi - Praktycznej Konferencji Aktualne Problemy Nowoczesnych Nauk - 2016. 111. Sp. z o.o. «Nauka i studia»: 55–61.
  5. ^ Shabelnikov, A.A. (2016). "SECU-3i PROGRAMMABLE ENGINE MANAGEMENT SYSTEM". Technology, Energy, Agriculture Transport AIC. 112 (2(94)). Vinnytsia National Agrarian University: 67–73.