Quick quiz.
I swapped to an electronic dizzy when we first built my engine.
From memory I never modified the wiring to give it a full 12V like I probably should have.
I was sitting thinking the other day, that this may have been the source of all my dramas with fouling plugs over the years due to a weakened spark.
To combat that issue and just because I could, I threw in an old MSD5 we had lying around and whalla, problem 99% solved.
Now because Im now running the MSD with an amplified voltage, does that mean I dont need to bother with the 9v-12v wiring change?
points to electronic dizzy (wiring change question)
Started by
orangeLJ
, Mar 17 2009 02:19 PM
10 replies to this topic
#1
orangeLJ
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Posted 17 March 2009 - 02:19 PM
#2
_NZ Toranaman_
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Posted 17 March 2009 - 03:28 PM
What I did was run a 'hot' wire from battery to key then key to coil. 13.8-14.0 volts.
The old days we could hot wire a car from battery to coil then jump a screw driver across the starter as they never had steering locks.
The old days we could hot wire a car from battery to coil then jump a screw driver across the starter as they never had steering locks.
Edited by NZ Toranaman, 17 March 2009 - 03:30 PM.
#3
Rockoz
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Posted 17 March 2009 - 04:24 PM
Would 25% extra spark be beneficial? Probably.
#4
VitcLJ
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Posted 17 March 2009 - 05:44 PM
MSD claim that the MSD5 unit will work down to 5 volts. I would still personally re- wire the resistive wire from the ignition to the coil with a plain wire. (the resistive wire is usually pink).
#5
View GaragePosted 17 March 2009 - 06:03 PM
The unit will work down to low voltage, doesn't help the coil much
#6
VitcLJ
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Posted 17 March 2009 - 08:07 PM
The MSD 5 is a capacitive discharge system It produces the sparks by dumping a high voltage charged capacitor into the coil primary via electronic switches. This high voltage (according to their advertising blurb 370V to 450V) is produced by an onboard DC/DC converter. If its well designed then it will produce the same voltage to dump across the coil at 5volts as it will at 12 volts (in theory but don't know the circuit so can't really say it does for sure, reckon this could be the advertised spread). if you look at the wiring the coil-ve that is usually connected to the points is now only connected to the MSD orange wire which is the HV output of the module.
Wiring diagram is here http://www.msdigniti....pdf?terms=5200
Wiring diagram is here http://www.msdigniti....pdf?terms=5200
#8
orangeLJ
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Posted 18 March 2009 - 08:04 AM
That was my line of thought, the MSD is meant to produce the same charge no matter what the input voltage so I havent bothered with it but I was wondering if that was the case or not.
So I can stop worrying about it and cross something off the list then.
So I can stop worrying about it and cross something off the list then.
#9
_torbirdie_
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Posted 18 March 2009 - 09:10 AM
I wouldnt be so sure.That was my line of thought, the MSD is meant to produce the same charge no matter what the input voltage so I havent bothered with it but I was wondering if that was the case or not.
So I can stop worrying about it and cross something off the list then.
This misconception that could cause trouble here is that you have 9V with the normal resistance wire.
No. The resistance of the msd unit will be most likely much lower than the points sytem coil and it will be drawing a much higher current, lowering the voltage at the end of the resistance wire even further. Do appreciate that even on a points system the coil is only getting about 6-7V across the primary circuit when there is a current going through it.
Edited by torbirdie, 18 March 2009 - 09:13 AM.
#10
orangeLJ
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Posted 18 March 2009 - 09:23 AM
That actually makes sense (I had to read it a couple times to get my head around it)
But basically you are saying that the current draw of the MSD could outweigh the capabilities of the resistance wire?
If I use the 9v wire to power a relay, I can run a 12v source from my starter (battery is in the boot) and use the original wire to click the relay on/off for 12 volts to the msd?
I left all the original wiring in the engine bay as a just in case kind of thing, but maybe once its in the new shed its time to sort it out.
But basically you are saying that the current draw of the MSD could outweigh the capabilities of the resistance wire?
If I use the 9v wire to power a relay, I can run a 12v source from my starter (battery is in the boot) and use the original wire to click the relay on/off for 12 volts to the msd?
I left all the original wiring in the engine bay as a just in case kind of thing, but maybe once its in the new shed its time to sort it out.
#11
_torbirdie_
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Posted 18 March 2009 - 09:43 AM
That actually makes sense (I had to read it a couple times to get my head around it)
But basically you are saying that the current draw of the MSD could outweigh the capabilities of the resistance wire?
If I use the 9v wire to power a relay, I can run a 12v source from my starter (battery is in the boot) and use the original wire to click the relay on/off for 12 volts to the msd?
I left all the original wiring in the engine bay as a just in case kind of thing, but maybe once its in the new shed its time to sort it out.
Yes, its likely that you could overload the resistance wire, its really only rated for 5 amps or so.
sounds like you are comfortable setting up a relay, so go with that.
This is neither here nor there but: Best to call it the resistance wire rather than the 9v wire, it will have the same voltage as all the other wires unless its passing a significant current, which it wont be if used as a trigger wire for a relay.
Edited by torbirdie, 18 March 2009 - 09:47 AM.
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