Ive been thinking about ignition systems lately after installing the pertronix ignitor II on my GS. Seems to run a little smoother using the stock coil, but no power increase or anything that i can tell. I thought about how a large majority of newer vehicles are switching to coil on plug ignition systems for increased spark energy and reliability and such, which led me to think about making such a system for my car. Tell me if you think this will work. Modify the distributor cap and rotor to have rotor ride along a ring inside of the distributor, having a solid contact with the terminal ends, say with another stainless sprung contact like for the coil wire in the center of the rotor, but use this on the outer terminals instead of a spark gap. Then hook up what was the coil terminal to a solid ground connection. Then hook up small wires from each cylinders ign. terminal in the dist. cap, and run each wire to the coresponding ignition coil mounted on the valve covers. This way when the ground is made up by contacting one of the terminals inside of the cap, it will charge the correct coil, and when it loses contact with the terminal the coil will fire the plug, just like how points work. I could modify the terminals inside of the distributor cap to increase coil charging time by making the terminals contact for a larger degree of rotor travel. I could use regular type ignition coils i guess, or if E-core coils are more energy efficient i would rather use those since they are a smaller package and offer more spark energy. Has anyone done this before? Would it even work? Am i getting all of the picture here? This is just something i thought sounded cool, and would possibly make a newer style ignition setup pretty cheap to build & adapt to the older cars. Please reply with your thoughts. Thanks
Possibilites exist using this idea, however, there are several problems. One is that the coil used will require a specific waveform to trigger it, rather than a simple switch. The original coil, condenser, and points create a "resonant" circuit, which is necessary to properly match the coil being used. The second is that, when the coil fires, the primary voltage will may rise fast enough to cause crossfiring. In this case, the primary winding becomes the secondary, which is how the OBDII ignitions check ignition performance.
What would be the benefit? I think the newer systems are used to control spark advance on individual cylinders for knock control.
I really cant say that there would be much added benifit other than slightly smoother running, more spark energy at higher RPMs possibly, less plug wire length for less resistance, etc. I used to own a RX7 and a big thing to do with the earlier cars was to switch it over to use individual coils per rotor on the leading plugs which resulted in smoother power and more torque due to increased spark energy from longer coil charge times? The 2nd generation RX7s incorporated this from the factory. Nothing really necessary, im just always up for trying new ideas to see how things work out. Cant hurt to try it, ive got time. How exactly does this resonant circuit work? Could you describe it to me or give me a link? I might be able to figure out a way to make it work if i understood a little more about how the normal system works. Thanks for the input.
Yeah, I know what you mean. i like to think about doing stuff like this too. I just don't think you could beat an msd system for a good hot spark.
Actually i figured i would end up using a msd type system with the multiple coils if it were possible. Definately ignition system overkill. I was hoping to maybe have enough spark energy to use surface gap spark plugs, or clipping the ground electrode off so i could have more spark exposure and still have a extremely hot thick spark. Later
RABarrett, if your still around would you mind explaining to me the resonant circuit idea? Its something i'd like to understand. thanks
Resonance is the concept driving ALL frequency sensitive components. It simply means that any frequency sensitive component will respond better to some frequencies than others. Capacitors, inductors, and transformers are frequency sensitive, meaning that they are optimized to a particular frequency, usually where most used. HEI, for example, is optimized for low rpm use, where it is most used. The result is that thios system's resonance is better at these frequencies, or rpm, usually below 3500 rpm. Above this rpm, the spark tends to slowly lose energy, reducing the spark intensity. It is fine for stock applications, where the effective compression is limited. When using power adders, such as different camshafts, or a blower or nitrous, the demand for spark can exceed supply, causing missing, backfire or complete shutdown of the engine. The concept of the individual coils mainly reduces the demand on the coil, requiring only charging one spark plug, instead of all of them. It also allows misfire monitoring, which I will explain in the next submission. Ray
Update Alright, ive been pretty busy with schoolwork over the past month or two and havent been able to get much done on the cars, but ive managed to build the prototype for the ignition system using a modified stock cap and rotor. I drilled out the terimals in the cap and in their place, i installed some sprung "tappets" that extend up out of the top of the cap and sit on small stainless disks that act as extention limiters to restrict the vertical travel. Each tappet has brass screw terminals on the end to attatch to the negative coil leads. They have about a quarter inch of vertical movement at the moment, which is more than enough. I have some springs for check valves coming from 1/3 psi, 1 psi, and 5 psi check valves which should be a good start. I made a set of stacked disks with a small "window" cut out to break the ground. This area will be filled with epoxy to maintain a level surface for the tappets to ride along. Each terminal will have its own capacitor, although i havent purchased the capacitors yet. Ill probably use standard points caps for the first tests. Only downside is the material used is mainly aluminum, which will most likely wear out soon. However the project has only cost about 10 dollars at the moment, so if it proves to have great potential i can have stainless components made. I still dont know if it will work, but lets hope it does. Ill post some pictures someday when i get the chance, and update whenever i feel like it as well. Later :3gears:
I imagine that at some speed there won't be enough time for the sprung tappets to return to their starting position. Going one step further to eliminate the mechanicals, one could use an LED and opto reciever to trigger it electronically. A power switching transisitor would then be used to switch each coil on and off.
Well, with the current design the tappets do not move. They more or less just ride along the plate with the spring pressure keeping them in contact. The plate is smooth with no bumps or anything, so i shouldnt have any trouble with what we could consider "ignition tappet float"
Since most of you are looking at mechanical means of triggering, a lot of wear would occur. The use of a transistor would require the use of a computer to control the coil fired, depending on firing order. Some of the present ignitions use the coil high voltage as an output, using it as a point signal to the ignition. Though the idea is a good one, the main reason it is used on new vehicles is to determine misfire, should it occur. It is used mainly by the OBDII system for emission control. Ray
True that. Thats the only downside that i can really see with a mechanical setup is wear. I think with enough engineering it could function nearly as accurately as an electronics setup, any difference would be negligable. Its just free of all the wires/clutter and is cheaper to maintain. Im basically reverting back to a points type ignition i guess. If it works, replacing the stuff should only happen every oil change or two, which isnt bad to me. On the mechanical stuff, ill be using twin bosch K-jetronic mechanical fuel injection systems from audi 5000 turbo's. Already have them ready to go, just need to fab up an intake. RABarrett, Since you know about how all this stuff functions together, do you have any tips on optimizing the ignition system ive discussed? Anyone having any insight into the size of the gap in the rotor(the one that breaks the ground) it would be nice to have some other peoples opinions. Later
I applaud your work. I love it when people think out side the box and do not relie on a credit card and a summit catalog. It is a little more satisfying when you can make it your self rather then just opening up your wallet.
