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Re: ? about Mopar elect. dist. [Re: B1MAXX] #2868698
01/03/21 11:28 PM
01/03/21 11:28 PM
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most likely, it's just a trigger so the ECU knows when to fire the coil. Back in the days of points the points would both charge the coil and cause it to fire when they opened. With the advent of electronic ignition the ECU would charge the coil and the pickup would trigger the ECU to fire the coil.

Re: ? about Mopar elect. dist. [Re: dragon slayer] #2868914
01/04/21 04:03 PM
01/04/21 04:03 PM
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Originally Posted by dragon slayer
Once you added a computer and the conditioned 5V power source going a different route was easier. The cars where not built to be performance racers, heck the first version still used points, but with a CD ignition system and the points only fired a simple transistor at low current. Then it was crank triggers.


You are right as I remember looking at how some of the point operated electronic and CD ign was wired. I believe Mopar , Ford and GM all had point triggered electronic CD ign in the later 60's. And you are also right about the basic ECU not having the 5 volt system that once they went to a Fuel injected PCM they had to have a 5 volt circuit. Ron

Re: ? about Mopar elect. dist. [Re: 383man] #2868944
01/04/21 05:03 PM
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To be honest, they didn't have to have a 5v setup. there are ways to have conditioned the old style signal to be compatible, but it was cheaper to go the way they did if they were already adding a bunch of sensors and such that used 5v. I am putting a dual TBI setup on my 51 Plymouth's flathead and am using the old school mopar electronic ignition distributor guts from a /6 in my 51's distributor as the ignition trigger.

Re: ? about Mopar elect. dist. [Re: Sniper] #2869173
01/05/21 01:02 AM
01/05/21 01:02 AM
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[quote=Sniper]To be honest, they didn't have to have a 5v setup. there are ways to have conditioned the old style signal to be compatible, but it was cheaper to go the way they did if they were already adding a bunch of sensors and such that used 5v. I am putting a dual TBI setup on my 51 Plymouth's flathead and am using the old school mopar electronic ignition distributor guts from a /6 in my 51's distributor as the ignition trigger. [/quote

I just meant once they went to 5 volts to work all the sensors as you said then it was easy to go with Hall Effect. Good luck with your 51 as it sounds like a cool ride. Ron

Re: ? about Mopar elect. dist. [Re: 383man] #2869215
01/05/21 09:35 AM
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I said that originally. As I also stated points where used to trigger CD type box. Points are opening against a higher current flow for a normal point system, hence the blue spark and wear to contact surface. In the petronix race set up the points no longer directly fired the coil. The coil is charged and discharged through the large power transistor that is heat sunk on the large hunk of aluminum. The points just handled a much smaller milliamp lever of current to fire a circuit to turn the power transistor off. That is why they moved to the shorter and smaller contact surface points. They could handle much higher rpm without bounce. If you used them as normal points though, they would wear out much faster because of the smaller contact area.

Through resistors, capacitor you can create electronic filters (high or low freq pass). So that AC input signal that looks like DC pulses but is considered AC because it reverse polarity can be cleaned up to simple negative pulses never even seeing the positive voltage spike. Early transistors needed a higher Vbase typically to fire. .5 to .7V range. New stuff much lower voltages, plus the move to FETs and who know what now. Let alone what can now be done by a microchip controller.

Re: ? about Mopar elect. dist. [Re: dragon slayer] #2869319
01/05/21 02:15 PM
01/05/21 02:15 PM
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Originally Posted by dragon slayer
I said that originally. As I also stated points where used to trigger CD type box. Points are opening against a higher current flow for a normal point system, hence the blue spark and wear to contact surface. In the petronix race set up the points no longer directly fired the coil. The coil is charged and discharged through the large power transistor that is heat sunk on the large hunk of aluminum. The points just handled a much smaller milliamp lever of current to fire a circuit to turn the power transistor off. That is why they moved to the shorter and smaller contact surface points. They could handle much higher rpm without bounce. If you used them as normal points though, they would wear out much faster because of the smaller contact area.

Through resistors, capacitor you can create electronic filters (high or low freq pass). So that AC input signal that looks like DC pulses but is considered AC because it reverse polarity can be cleaned up to simple negative pulses never even seeing the positive voltage spike. Early transistors needed a higher Vbase typically to fire. .5 to .7V range. New stuff much lower voltages, plus the move to FETs and who know what now. Let alone what can now be done by a microchip controller.



Your right as I understood right away that the points in the electronic CD ign only carried a low current compared to normal point ign systems. That was one of the good features about them way less point wear and much more point life with more spark. Ron

Re: ? about Mopar elect. dist. [Re: 383man] #2871043
01/08/21 12:38 PM
01/08/21 12:38 PM
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Just a update I did get it to run on falling edge.....The dist. had to be advanced significantly from where it was at rising edge.

Re: ? about Mopar elect. dist. [Re: B1MAXX] #2871177
01/08/21 03:56 PM
01/08/21 03:56 PM
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was there any increase in performance doing that ?
beer

Re: ? about Mopar elect. dist. [Re: moparx] #2871515
01/09/21 10:34 AM
01/09/21 10:34 AM
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Not sure yet from a run through the gears, full throttle stab...but It did change the idle, sounds better, and if I hold it steady at 5000 It sounds different now too. The timing, after adjustment, seems to be the same but the idle is completely different. Don't know why. If I had to guess it would be that the trigger point is more consistent, event though I couldn't see it in the light. It could have been a rotor phasing issue before also with a different trigger point. They will run both ways though.

Re: ? about Mopar elect. dist. [Re: B1MAXX] #2871628
01/09/21 02:07 PM
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What do you mean by rotor phasing? At low RPM your giving a cleaner signal in to the box as discussed earlier; off that falling voltage. So I imagine it did clean up your idle. That is what the box wanted. You had to reposition the distributor to get the correct timing for the back side of the reluctor tip.

Re: ? about Mopar elect. dist. [Re: dragon slayer] #2871655
01/09/21 02:41 PM
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Same box here - Pertronix digital HP, and I set mode 9 to 4000 for "magnetic trigger falling edge". Still using stock dizzy but I replaced the Mopar ecu with this box. Timing was nearly same as it was before. Using this box because it has start retard which is mode 7- and I set that to 4500. My initial is 24 degrees.

Re: ? about Mopar elect. dist. [Re: dragon slayer] #2871997
01/10/21 10:10 AM
01/10/21 10:10 AM
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Originally Posted by dragon slayer
What do you mean by rotor phasing? At low RPM your giving a cleaner signal in to the box as discussed earlier; off that falling voltage. So I imagine it did clean up your idle. That is what the box wanted. You had to reposition the distributor to get the correct timing for the back side of the reluctor tip.


Position of rotor to term. in cap at time of spark. Was thinking changing trigger point would move this.

These replaced MSD's. I wonder if MSD is a rising edge set up? Because just changing the box leaving all else the same it would only run on rising edge.

Re: ? about Mopar elect. dist. [Re: B1MAXX] #2872351
01/11/21 12:34 AM
01/11/21 12:34 AM
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I remember having a RB motor on a engine dyno that had aftermarket magnetic pick up distributor female plug that wouldn't plug into the Mopar ECU boxs so I adapted a Mopar type male mag pickup plug onto it and I didn't know the color code of the Mopar mag pick up versus the after market and of course I got them reversed. the motor wouldn't start on he dyno until I retarded the distributor a bunch.
Luckily the dyno operator recognize the symptoms and we fixed it, it was 40 crankshaft degrees difference in having it wired the correct way and having it reversed shock


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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