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Technology, old cars, & other stuff...


Saturday 28 January

ECU Design

With the basic Fuel Injection proven on the Mini it was time to design and build a "proper" version of the Engine Control Unit (ECU) that would be more reliable with a more capable microcontroller to allow expansion and more advanced functions. So, the Arduino 2560 was chosen for the microcontroller and a basic design similar to below was sketched up.



Using the excellent Design Spark 7.1 from Radio Spares, the circuits were drawn properly and the printed circuit board layout was designed. The power tracks had to be manually routed to ensure the shortest runs as well as some critical signals such as the crankshaft position pulse. The remainder was auto-routed then adjusted manually.

The board was manufactured by Quick Teck, a UK company but with back-end PCB fabrication done in China. The resulting PCB's were delivered on-time and turned out to be excellent quality.

Here's the first board partly assembled, fitted for a Dual Port application:


Some components are fitted to the underside to make the most of the real-estate:


This ECU has the following capabilities:

  • Opto-isolated Crankshaft and Camshaft position inputs from standard automotive Hall-Effect sensors
  • 4 Injector Outputs with Regulated Injector Supply
  • 2 Coil Pack outputs for Wasted Spark Ignition
  • Electric Cooling Fan relay control
  • Stepper motor drive for automatic idle speed control
  • Over-voltage protected inputs for Narrow Band Lambda, Throttle Position Sensor, Coolant Temperature, Air Temperature and Vehicle Voltage
  • On-board Manifold Absolute Pressure sensor
  • Synchronisation output for timing calibration
  • Additional opto-isolated digital input and expansion board capability for custom applications
  • Full 3D interpolation between map values on Fuel and Injection Maps


 Here's the unit assembled, ready to be fitted in a car:

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