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John T
11-19-1999 13:39:18
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Re: J.D. G Ignition system (Need Advice John T.) in reply to Gman, 11-19-1999 06:59:39
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G man, well Im gonna tell you how they work and in so doing maybe we can figure the answer, but I think one MSD control unit for sure and one or two magnetic pick up coils (regardless if in 1 or 2 distributors) will do the trick. OK, you definitely wanna run elec ignition instead of points and you already said that. Well, in elec ignitions, the points are replaced by a magnetic pickup coil of wire that gets a voltage pulse each time a magnet on the distributor lobe passes near it just like when the cam opens the points to fire the coils. Each time the coil of wire gets a voltage impulse from the pickup coil in the distributor, the elec control unit fires the coil and any plugs attached to them via a distributor. One control unit will fire both plugs (it fires 8 in a V8 easy enough), because when the coil fires, its the distributor rotor tip that directs it to one certain plug. And it fires when the dist magnet tells it to, so Im not even sure why you want dual distributors at all, as the MSD control unit and their high energy coils can deliver more spark energy than you will ever need and they are plenty fast to fire 8 cylinders at 8000 rpm so they can sure as hell fire two at 3000. The trick is to get a distributor or one made with its magnetic lobes in the right place at right time to fire each cylinders plug at that darn 0 and 180 then 540 coast times. Now another limiting factor we need to think about it sounds like your gonna try and fire two or more plugs at same time right??? Well, if you wire more than one plug to one coil in parallel, if one plug had a much lesser gap resistance, it may well fire first leaving a wimpy firing on the other under certain circumstances. If your gonna fire a bunch of plugs at same time, Id rather see each have its own coil like they do on marine engines but I think you may be overkilling a bit here. Then the question is, whats the current rating on the elec control unit and does it have the capacity to supply multiple coils in parallell?? MSD can answer that and I suspect it may handle two coils in parallel, but not 3 or 4. The elec control unit is a current supplier, thats what fires the coils and plugs, current. On race cars one unit fires one coil but it does it 4 times per crank revolution. The reason people went to Mallory dual point distributors in the old days was the fast rpms made it difficult to stop point float, so two points only had to open and close 1/2 the time but you have no such crucial times when only firing two cylinders even at 3000 rpm. Why not go with one MSD control unit, one coil, and an over the counter high performance after market elec pickup type distributor?? Ive wired Chrysler and Fords all cross bred and any old magnetic dist unit always fired any control unit I hooked to it, so Im saying the MSD unit and its high energy coil SHOULD work with anybody elses elec pickup distributor if you want more spark energy that the cheaper unit supplies. Now, if you go to dual distributors, each one has its own mag pick up and either of its signals would fire a single MSD unit just fine. I guess then you would have a coil for each distributor right??? But then, each coil would fire each time the other one did (if the MSD can supply 2) but isnt that the same thing a Wico mag does anyway to fire each time up even if on exhaust stroke?? Hell this is gettin too deep, I say fire only one plug per coil and see how many coils the MSD control unit can supply, then we can talk again. I think two plugs per cylinder is all you need, The head is far superior than the cylinder wall side (like the Old Chrysler Hemis) and I fear two explosion shock waves from two different directions may cancel each other out and spark knock anyway, so I would put two plugs (if you insist) only in the head. So one MSD unit could work, but its figurin out how many coils it can fire, but with only one unit, it would still have to fire each cylinders coil banks even on their exh stroke it looks like. Since it fires them all them, if u had two on each side, thats 4 coils youre tryin to fire with one unit (too many) so you prob would need two units if you insist on two plugs and two coils per cylinder. Enough, Im confused, just try a single elec distributor with a single MSD unit and high energy coil with a single plug in the head, and I bet you wont tell the difference ?? I think its compression and rpm (HP = function of torque x rpm) more so than ignition, after you got MSD type high energy anyway, it works in race cars at high rpm and high compression just fine. Let me know how bad I confused you. Ol John T in Indiana never at a loss for words (Im also an attorney remember)
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