Building an Engine Controller: The Interfaces

With the distributor signal capture, conversion and subsequent use by the microprocessor the injectors and plugs have to be mated to the processor. A similar thing has to be done for the relays for the monitor board. For the relays there are any number of Arduino compatible relay boards available. Typically these contain opto-isolators so you have to take the output pin LOW to turn the relay on. That's the case here. For the fuel injectors I am using high impedance ones so they can be turned on and off with a MOSFET without a  resistor in-line. For the Coil on Plugs (COP) there are usually 2 and 3 wire systems. I'm using a 3 wire set-up so that the TC4469 gate driver can drive them directly.

Building an Engine Controller: The microprocessor

Obviously to run the whole thing I need a microprocessor. There are some great products out there to help in a build like this. Most of the work I have done in the past has been using PIC products. This required working in Assembly which I don’t particularly care for. I don’t know what the current state of affairs is with PIC these days so I really can’t say. Fortunately there are a number of suites to build a system using C++ as the programming language. I’ve used both the ST Micro STM32 system and the Arduino based system in various builds. I prefer the Arduino system because a lot of work has been done by other people and various routines are freely available. I also like the Arduino IDE suite. One other important factor is the footprint required. I chose to use two Arduino Nano boards for this build.

Building an Engine Controller: The Signal

Any engine control unit uses crankshaft and camshaft position to determine the timing of the various events needed to run an engine. The D16 series Honda engine has three variable reluctance (VR) wheels located in the distributor. The first wheel has one tooth on it which provides an index for the other two wheels. The second has 4 teeth on it and are positioned such that the pistons are at top dead center (TDC) when the tooth is positioned over the magnet. Finally the third wheel has 16 teeth on it to provide a crankshaft position signal (CPS). A photo of the interior of the distributor and a three dimensional drawing of the Honda VR wheels is shown.

Building an Engine Controller

As part of my longstanding planning for having independent back-up services for my property I wanted to develop a standalone power unit for running a generator head with enough capacity to run the well, the house and outbuildings, and some extra capacity. A quick back of the envelop calculation told me I needed about a 20kW generator (40 HP input required using gasoline for fuel). Generators like this can be purchased but I wanted a power unit with the following characteristics. Any new parts needed for it can be readily replaced at low cost and can be held in storage with a small storage volume. It should have multi-fuel capability. It needs to be robust and have a long service life under difficult conditions.