Ignition options?
10-02-01, 07:49 PM
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Ignition options?
Ok, the car is a 79, so this means it still has points and low voltage coils. I want to convert to direct fire, but do I need to get rid of the points first? Can I bolt in igniters from a newer car or do I have to change the whole dist? Should I just slap an MSD on it? and trigger it by points? That sounds like a REALLY bad idea but its an option 
Can I run the stock coils at 12v or will they fry?
What should I do?
Can I run the stock coils at 12v or will they fry?What should I do?
10-03-01, 12:26 AM
#2
RicanRider
You will need to upgrade your ignition by upgrading the complete distributor. You will not be able to use the same coils. You will need either the MSD or a replacement for electronic ignition system. So before you can convert to direct fire you need to take care of upgrading to an electronic iginiton system first....
10-03-01, 12:33 AM
#3
8krpm is not enough
that's not 100% true. The MSD box CAN be triggered by a points system. You just connect the leading coil's old negative line to the white trigger wire of the MSD box and then use a pair of 12V coils like paul yaw / max7's site shows.
It's probably a BETTER IDEA to convert to electronic ignition because you get the benefit of the better dizzy, higher voltage leading ignition (better emissions and gas milage there alone), no more adjusting the points now and then, and you can use Jeff20B's dual leading ignitor direct fire system if you like instead of the MSD box.
converting to an 81+ style electronic ignition isn't that hard nor that expensive if you can find the parts at a junk yard / on ebay.
just my .02.
--matt
It's probably a BETTER IDEA to convert to electronic ignition because you get the benefit of the better dizzy, higher voltage leading ignition (better emissions and gas milage there alone), no more adjusting the points now and then, and you can use Jeff20B's dual leading ignitor direct fire system if you like instead of the MSD box.
converting to an 81+ style electronic ignition isn't that hard nor that expensive if you can find the parts at a junk yard / on ebay.
just my .02.
--matt
10-03-01, 01:46 AM
#4
No, you can't bolt in ignitors on a points dizzy.
I'll get to that.
When you ask if the coils could run at 12V, I'm sure they could, for a while. It's the points I'm worried about. You have an ignition switch that has two seperate 12V ON wires. One is on when the key is on. The other is on only when the key is in the start position. Rather, two wires are switched on in the start position. They are part of a single throw double pole switch which means the starter motor is engaged at the same time that the points are getting a full 12V - during cranking. As soon as the engine starts you let go of the key and it witches to the ballast resistor circuit. This lowers the 12V down to something like 9 or 8 or possibly 6 volts to try to keep points from burning/pitting too much. Heh, it can and will still happen though if other things in the circuit aren't working well.
I suspect racers in the olden days tossed the ballast resistors so the coils (and points) got a full 12V (or 13.8V or whatever) during a race. Then before the next race they would swap the used points with new points and set them properly and be ready to go again. Any old racers out there care to comment?
Mazda could have gone with a points triggered CD ignition system like some auto manufacturers did in the 60s and 70s, but didn't. It would have lengthened the points' life considerably because of the much lower amount of electricity required to switch a transistor. Only rubbing black wear would be a factor (possibly other pointsy issues too that I don't care to think about like floating/bouncing at high RPM/vibration). The technology was out there, and Mazda most likely would have used it if they knew it would be good to use on a rotary, what with emissions laws getting stricter every years and all (look at how good they improved the rotary engine from the early 70s' 10A to the '79 RX-7 12A). Why? Because the nature of a CD spark is a short, high voltage but low amperage spark. That is the most likely reason why Mazda kept using points and never used a CD spark ignition system. Or maybe their ignition department was full of Boeing employees (the lazy B). Hah, I doubt it. Look at the '73 12A. It has dual distributors. Look at the '76 Cosmo, it has a dizzy with 3 points in it. Huh?
To get back to your question...
I wonder if points could handle the amount of amps necessary to fire two coils in direct fire. A ballast resistor lowers the voltage through the points, but does it really lower the amps? I bring this up because there is a way to run direct fire with points using stock coils. I'm just not sure whether to hook dual 13J or 13E coils (I forget which one is Leading) to the Leading points in series or parallel. Is it the volts or amps that burns points? (hey, I didn't use any apostrophies with all those plurals. So why do so many others use them? Oops, that's a topic drifter right there. I only sometimes mess up its and it's)
I've still got to recommend against using an MSD on a rotary, even one with points. The spark duration of points is still longer than the MSD capacitive discharge spark (it's that whole 3 grand thing and the RPM where a rotary spends most of it's life reving in/above). Oh sure you can hook an MSD to your points coil or coils and it will work as well as expected, but chances are you will end up spending money on only one MSD box because justifying the purchase of a second MSD for Trailing would be rather expensive. The Leading/Trailing split might be a steady 8* at idle, but check it again at 6kRPM.
An MSD greatly improves an old '68 "Camro" with a stock points distributor, but it degrades a rotary with an '81-'85 distributor.
Do yourself a favor. Spend your money on an '81-'85 distributor and 3 Diamond (or other similarly rated) coils and 3 J109 ignitors. You'll most likely be able to get all those for the same price of a single MSD box. I know I did.
Since you're kinda new at this, the dizzy should already have 2 ignitors on it, unless the seller has already removed them to sell seperately. I wouldn't blame him, those things are in high demand because of the high profit margin. Try to get a good deal.
I'll get to that.
When you ask if the coils could run at 12V, I'm sure they could, for a while. It's the points I'm worried about. You have an ignition switch that has two seperate 12V ON wires. One is on when the key is on. The other is on only when the key is in the start position. Rather, two wires are switched on in the start position. They are part of a single throw double pole switch which means the starter motor is engaged at the same time that the points are getting a full 12V - during cranking. As soon as the engine starts you let go of the key and it witches to the ballast resistor circuit. This lowers the 12V down to something like 9 or 8 or possibly 6 volts to try to keep points from burning/pitting too much. Heh, it can and will still happen though if other things in the circuit aren't working well.
I suspect racers in the olden days tossed the ballast resistors so the coils (and points) got a full 12V (or 13.8V or whatever) during a race. Then before the next race they would swap the used points with new points and set them properly and be ready to go again. Any old racers out there care to comment?
Mazda could have gone with a points triggered CD ignition system like some auto manufacturers did in the 60s and 70s, but didn't. It would have lengthened the points' life considerably because of the much lower amount of electricity required to switch a transistor. Only rubbing black wear would be a factor (possibly other pointsy issues too that I don't care to think about like floating/bouncing at high RPM/vibration). The technology was out there, and Mazda most likely would have used it if they knew it would be good to use on a rotary, what with emissions laws getting stricter every years and all (look at how good they improved the rotary engine from the early 70s' 10A to the '79 RX-7 12A). Why? Because the nature of a CD spark is a short, high voltage but low amperage spark. That is the most likely reason why Mazda kept using points and never used a CD spark ignition system. Or maybe their ignition department was full of Boeing employees (the lazy B). Hah, I doubt it. Look at the '73 12A. It has dual distributors. Look at the '76 Cosmo, it has a dizzy with 3 points in it. Huh?
To get back to your question...
I wonder if points could handle the amount of amps necessary to fire two coils in direct fire. A ballast resistor lowers the voltage through the points, but does it really lower the amps? I bring this up because there is a way to run direct fire with points using stock coils. I'm just not sure whether to hook dual 13J or 13E coils (I forget which one is Leading) to the Leading points in series or parallel. Is it the volts or amps that burns points? (hey, I didn't use any apostrophies with all those plurals. So why do so many others use them? Oops, that's a topic drifter right there. I only sometimes mess up its and it's)
I've still got to recommend against using an MSD on a rotary, even one with points. The spark duration of points is still longer than the MSD capacitive discharge spark (it's that whole 3 grand thing and the RPM where a rotary spends most of it's life reving in/above). Oh sure you can hook an MSD to your points coil or coils and it will work as well as expected, but chances are you will end up spending money on only one MSD box because justifying the purchase of a second MSD for Trailing would be rather expensive. The Leading/Trailing split might be a steady 8* at idle, but check it again at 6kRPM.
An MSD greatly improves an old '68 "Camro" with a stock points distributor, but it degrades a rotary with an '81-'85 distributor.
Do yourself a favor. Spend your money on an '81-'85 distributor and 3 Diamond (or other similarly rated) coils and 3 J109 ignitors. You'll most likely be able to get all those for the same price of a single MSD box. I know I did.
Since you're kinda new at this, the dizzy should already have 2 ignitors on it, unless the seller has already removed them to sell seperately. I wouldn't blame him, those things are in high demand because of the high profit margin. Try to get a good deal.
Last edited by Jeff20B; 10-03-01 at 01:49 AM.
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