Building An Ignition System

Discussion in 'The Projects Forum' started by RobDean, Feb 4, 2012.

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  1. RobDean

    Thread Starter New Member

    Feb 3, 2012
    Hello everyone,

    This is my first visit to your forums and it looks very knowledgable and helpful, judging from the few posts I've read when searching for previous posts that might be useful to my projects.

    By way of introducing myself, let me say that I have no real practicle experience in designing and building microcontroller projects. But I have taken a couple of personal interest courses at the local community colleges in general electrical theory, electronic and semiconductor devices, and various levels of computer programming. These were some time ago, late '90's, and have been pretty much neglected since then.

    I actually did put in some time in one of those classes learning a bit about microprocessors on a Heathkit trainer that used the 80C85. It had a small LCD screen so you could see what you were doing and a Watchdog program to keep you from doing any really bad things to the thing, I guess.

    I was introduced to the CPU instruction set then so that is not completely voodoo to me. I have programmed a bit in a couple of Basic dialects and also (still got the discs around here somewhere). I know nothing of C, Fortran, Cobol, or any of the other languages.

    So I am not a Wiz and probably never will become one. I took these classes out of curiosity and a desire to at least get a basic understanding of how computers, controllers and industrial control devices actually functioned. I probably know just enough to get myself into serious trouble if I ever tried to do any of this stuff professionally.

    I enjoy working on my old F150, except when I feel like blowing it up, and I want to make it run as good as possible. I have become increasingly unhappy with the Ford EEC-IV control box that the factory stuck in there and hope to build my own set of engine control units. One to run the ignition system, one to run the fuel injector system, and one to run the electronically controlled transmission.

    I am also becoming more interested in robotics and have a few projects I would like to have a go at, but I want to deal with my truck first. The ignition system looks like a fairly easy place to get started. The only real problem areas that I have run into while trying to think it through, in a flow chart sort of way, is the problem of trying to set off that spark plug before the actual TDC signal for that cylinder ( the ignition advance ) and the very short time between ignition events at high rpm ( the coil dwell problem ).

    I have found a set of GM LS2 truck type coil banks that I would like to use. That means 8 individual coils, and they have a dwell requirement of 5ms each to charge them. So I need 8 output lines, one for each coil, and at least one input line for the tach signal.

    Sequentially running 8 fuel injectors is essentially the same set of problems, with the opening of the injectors acting sort of like the ignition advance, and the duration of that opening acting sort of like the ignition dwell. With fuel tho, there are other considerations that must be taken into account and will require more inputs from the motor than just a tach signal. Air flow, air temp, engine temp, engine load, etc. So I'm going to save that for a bit later.

    I've used the Megasquirt site as a resource just to look at how they do things. Cool product, outstanding support forums and such. Lots of good info. But expensive and they seem to have fallen into the trap of trying to run all the aspects of powertrain control in one box, like a factory ECU. I personally want to seperate the three areas I mentioned earlier as I feel that it is easier to build, diagnose and fix problems in smaller units dedicated to a specific task. They also seem to be going a bit over the top with all kinds of CAN, LAN, daughterboards, etc, etc. Not a putdown, really, just not the way I want to do things.

    So, let me post this. I have introduced myself and outlined what I hope to accomplish and it's becoming quite long. Hopefully a few of you guys will take an interest in this and ride along. I will definitely be needing some help as this thing progresses.

  2. RobDean

    Thread Starter New Member

    Feb 3, 2012
    Let me just add that I'm a very slow typist, usually one finger, two when I really get going. I will outline the way in which I hope to accomplish this ignition system and I'm not really sure if it will work as I envision it. I am not very familiar with microcontrollers and their data sheets, nor the programmers for them. So I could use some reccomendations both about that and perhaps also about the manner in which I hope to solve these problems. Any advice and suggestions will always be appreciated.

    I have crunched some numbers pertainent to this project and will post them next, but as I said, I'm slow and it will take some time.

    I look forward to meeting everyone.

  3. RobDean

    Thread Starter New Member

    Feb 3, 2012
    This vehicle is a '92 Ford F150. 5.8L V8 w/E4OD. Currently the factory speed density computer. Recent rebuild about 3,000 miles ago. Bored 60 over, stock cam, shorty headers, dual exhaust. Normally aspirated, factory EFI, ignition, air intake, everything pretty much box stock. A 6000 rpm motor max. Probably good for another 50-60k miles before it starts smoking too bad. I have another 5.8 motor for it, newer, bit higher performance but essentially the same. This one is going to serve as the testbed just in case I really screw up and destroy stuff.

    I would like to mount the boxes that I'm going to build inside the cab and not in the engine compartment. I see no reason to subject them to the underhood environment and would actually like to have perhaps a 3 line LCD screen on each to display a little useful info while the truck is running. I can use fully shielded cables out to the coils and dist., the distances aren't bad, a few feet.

    OK, so there's the vehicle description and the environment in which I want to mount the boxes, if that makes a difference in the microcontroller selection.

  4. bertus


    Apr 5, 2008

    I am closing this thread as it violates AAC policy and/or safety issues.

    6. Restricted topics. The following topics are regularly raised however are considered “off-topic” at all times and will results in Your thread being closed without question:
    Any kind of over-unity devices and systems
    Automotive modifications
    Devices designed to electrocute or shock another person
    LEDs to mains
    Phone jammers
    Rail guns and high-energy projectile devices
    Transformer-less power supplies
    This comes from our Tos:
    Terms of Service
    There will be enough sites where automotive questions can be discussed :
    Member selected automotive forums

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