Ignition physics for regular guys like me.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Hey man, I running a 1227730 speed density comp, and having issues with my L98 basic engine, they are on a LT1 manifold with an HEI up top where God intended....cause sparks and water don't mix and recently the driveability has been lousy due to misfires badly at idle to the point of putting the automatic in gear may well kill the engine.....so I have to be super quick on the gas.....computer is custom chip, no EGR, injectors sound identical with stethoscope......30-40 lbs on the adj. regulator steady reading......
so having the computer HEI on it, what is a prime failure with a set of symptoms like that???
HEI chip/HV coil? main reg coil under button, everything looks normal.....timing at 10*
any suggestions?? been through vacuum leaks....no go there....
so having the computer HEI on it, what is a prime failure with a set of symptoms like that???
HEI chip/HV coil? main reg coil under button, everything looks normal.....timing at 10*
any suggestions?? been through vacuum leaks....no go there....
Cruising
Joined: Aug 2017
Posts: 13
Likes: 0
No battery votage to the Coil !!!
Good morning, Question ; I lost Battery voltage on my 68 to the coil, and think the fusable link opened !!!! Engine turns over , but there's no spark. How do I rewire the problem, is there a way to do this without replacing the harness with a jumper wire .... all sugestions welcomed !!!! thanks
7th Gear
Joined: May 2019
Posts: 7
Likes: 0
Hello Mike,
This has been an excellent thread, I posted to it in 2019 and you were very helpful. A few more questions have come up.
1. How does the secondary affect the primary, if at all, both points and electronic systems, or is the primary totally independent of the secondary? That is, can items such as spark plugs, HT wires, rotor, etc. cause the primary to react in various ways. It seems to me in a transformer (which the coil is), the load on the output circuit will affect the input draw of the transformer. Can what is happening in the secondary effect the primary current? It seems to me the load on the ignition coil secondary would affect the primary current. I cannot find any solid information on this. I do see in your post #1 this thread, item 11 where you seem to indicate it does, but I may be interpreting that incorrectly.
2. In that same line of thought, whether the secondary load does or does not affect the actual primary circuit, will the secondary load affect the overall load on the coil, read as will it affect the heat of the coil. Can a secondary circuit issue cause the coil to overheat.
Thanks for any help you can provide.
Tom
This has been an excellent thread, I posted to it in 2019 and you were very helpful. A few more questions have come up.
1. How does the secondary affect the primary, if at all, both points and electronic systems, or is the primary totally independent of the secondary? That is, can items such as spark plugs, HT wires, rotor, etc. cause the primary to react in various ways. It seems to me in a transformer (which the coil is), the load on the output circuit will affect the input draw of the transformer. Can what is happening in the secondary effect the primary current? It seems to me the load on the ignition coil secondary would affect the primary current. I cannot find any solid information on this. I do see in your post #1 this thread, item 11 where you seem to indicate it does, but I may be interpreting that incorrectly.
2. In that same line of thought, whether the secondary load does or does not affect the actual primary circuit, will the secondary load affect the overall load on the coil, read as will it affect the heat of the coil. Can a secondary circuit issue cause the coil to overheat.
Thanks for any help you can provide.
Tom
Thread Starter
Tech Contributor
Joined: Jun 2004
Posts: 20,913
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
hello mike, Hey Tom. Thanks for the interesting questions below. I'll just put my answers in this, as I'm less likely to miss or forget one.
this has been an excellent thread, i posted to it in 2019 and you were very helpful. A few more questions have come up.
1. How does the secondary affect the primary, if at all, both points and electronic systems, or is the primary totally independent of the secondary? Well, they both can and will affect each other during the different phases of the ignition cycle of each cylinder event. that is, can items such as spark plugs, ht wires, rotor, etc. Cause the primary to react in various ways. Yes. The spark plug gap size and the cylinder pressure at the time of ignition are the two main determiners (if that's a word) of the magnitude of the secondary high voltage (flyback) pulse. The coil may try to output a higher voltage, but the plug gap breakdown voltage level/requirement will clamp the coil output from going any higher. it seems to me in a transformer (which the coil is), the load on the output circuit will affect the input draw of the transformer. True for a transformer, but remember the coil, with its secondary open-circuited due to the rotor gap and plug gap, is used as an energy storage component, not a real-time energy transfer component like a transformer. The current in the coil primary is therefore essentially determined by the inductance and resistance of the primary windings, and the time allotted for the dwell charge period. can what is happening in the secondary effect the primary current? It seems to me the load on the ignition coil secondary would affect the primary current. The secondary load won't affect the primary current, as there's no load on the secondary during the primary current dwell period. But, when the coil "fires", the secondary voltage ramps up until it gets high enough to cause the plug gap to break down, and then spark current flows. The primary experiences a similar voltage ramp up (flyback), but it will be noticeably less than the secondary voltage (the turns ratio makes the primary flyback voltage smaller). This flyback voltage on the primary windings is what causes points to arc over while the points are trying to move apart from each other. (As I mentioned in IIRC Page One, the condenser is therefore needed to supply an alternative path for the interrupted primary current to go into, rather than across the points.) I cannot find any solid information on this. I do see in your post #1 this thread, item 11 where you seem to indicate it does, but i may be interpreting that incorrectly.
2. In that same line of thought, whether the secondary load does or does not affect the actual primary circuit, will the secondary load affect the overall load on the coil, read as will it affect the heat of the coil. Can a secondary circuit issue cause the coil to overheat.
Thanks for any help you can provide.
Tom
this has been an excellent thread, i posted to it in 2019 and you were very helpful. A few more questions have come up.
1. How does the secondary affect the primary, if at all, both points and electronic systems, or is the primary totally independent of the secondary? Well, they both can and will affect each other during the different phases of the ignition cycle of each cylinder event. that is, can items such as spark plugs, ht wires, rotor, etc. Cause the primary to react in various ways. Yes. The spark plug gap size and the cylinder pressure at the time of ignition are the two main determiners (if that's a word) of the magnitude of the secondary high voltage (flyback) pulse. The coil may try to output a higher voltage, but the plug gap breakdown voltage level/requirement will clamp the coil output from going any higher. it seems to me in a transformer (which the coil is), the load on the output circuit will affect the input draw of the transformer. True for a transformer, but remember the coil, with its secondary open-circuited due to the rotor gap and plug gap, is used as an energy storage component, not a real-time energy transfer component like a transformer. The current in the coil primary is therefore essentially determined by the inductance and resistance of the primary windings, and the time allotted for the dwell charge period. can what is happening in the secondary effect the primary current? It seems to me the load on the ignition coil secondary would affect the primary current. The secondary load won't affect the primary current, as there's no load on the secondary during the primary current dwell period. But, when the coil "fires", the secondary voltage ramps up until it gets high enough to cause the plug gap to break down, and then spark current flows. The primary experiences a similar voltage ramp up (flyback), but it will be noticeably less than the secondary voltage (the turns ratio makes the primary flyback voltage smaller). This flyback voltage on the primary windings is what causes points to arc over while the points are trying to move apart from each other. (As I mentioned in IIRC Page One, the condenser is therefore needed to supply an alternative path for the interrupted primary current to go into, rather than across the points.) I cannot find any solid information on this. I do see in your post #1 this thread, item 11 where you seem to indicate it does, but i may be interpreting that incorrectly.
2. In that same line of thought, whether the secondary load does or does not affect the actual primary circuit, will the secondary load affect the overall load on the coil, read as will it affect the heat of the coil. Can a secondary circuit issue cause the coil to overheat.
Thanks for any help you can provide.
Tom
That's my thoughts this late in the evening. If I've missed or overlooked something (or if it just doesn't make sense) please let me know.
Regards,
Mike
7th Gear
Joined: May 2019
Posts: 7
Likes: 0
Thanks for the response. Obviously, I have some follow up questions!
1. " True for a transformer,but remember the coil, with its secondary open..."
Yes, I can follow the opens you mention. I was more concerned about the points opening and assumed the condenser in the primary would pass the varying current. Okay. If I look at an oscilloscope showing the secondary, it graphs the voltage. That voltage, in the early portion of the trace builds to a high level. No current flow yet. Then the current flows and the spark jumps. So to be clear, then the rest of the trace showing the voltage swinging up and down has no current flow associated with it?
So, if the spark required is high energy, I assume that high energy is supplied by high electrical usage. If the spark required is low energy, I assume the electricity usage is low. So if sometimes we use more energy, sometimes less to create the spark, and the coil primary input is fairly constant then it must always be drawing enough to meet the maximum energy needed? What happens to the maximum drawn by the primary when the secondary does not need maximum? (Not sure I am being clear???)
2. Then I have trouble following- sorry. You first say they can and will affect each other. Then you seem to say it is minimal. Then I hear they are separate, but when the spark fires the flyback is reflected in the primary?? I am sure it is me, but could you be more specific?
3. Part of the reason this had come up in my mind years ago was with a problem with repeated Nipon Denso distributor module failures. The modules were failing every few weeks. The initial assumption was too high primary current- and one possible cause too high alternator voltage. In checking the voltage at the coil + post, I noticed a spark jumping to my voltmeter lead, something I did not expect with 14volts. I also noticed the spark would even jump to a screwdriver tip. Someone had replaced the plug wires with copper wires. After replacing those with OEM suppression wires, the jumping spark at coil+ and the module failures both disappeared. I did not take this as coincidence, but I took it as the secondary clearly affecting the primary. Do you believe that was a valid conclusion? Is that what you are saying in your second to last paragraph? And would you have any clearer explanation?
Thanks again,
Tom
1. " True for a transformer,but remember the coil, with its secondary open..."
Yes, I can follow the opens you mention. I was more concerned about the points opening and assumed the condenser in the primary would pass the varying current. Okay. If I look at an oscilloscope showing the secondary, it graphs the voltage. That voltage, in the early portion of the trace builds to a high level. No current flow yet. Then the current flows and the spark jumps. So to be clear, then the rest of the trace showing the voltage swinging up and down has no current flow associated with it?
So, if the spark required is high energy, I assume that high energy is supplied by high electrical usage. If the spark required is low energy, I assume the electricity usage is low. So if sometimes we use more energy, sometimes less to create the spark, and the coil primary input is fairly constant then it must always be drawing enough to meet the maximum energy needed? What happens to the maximum drawn by the primary when the secondary does not need maximum? (Not sure I am being clear???)
2. Then I have trouble following- sorry. You first say they can and will affect each other. Then you seem to say it is minimal. Then I hear they are separate, but when the spark fires the flyback is reflected in the primary?? I am sure it is me, but could you be more specific?
3. Part of the reason this had come up in my mind years ago was with a problem with repeated Nipon Denso distributor module failures. The modules were failing every few weeks. The initial assumption was too high primary current- and one possible cause too high alternator voltage. In checking the voltage at the coil + post, I noticed a spark jumping to my voltmeter lead, something I did not expect with 14volts. I also noticed the spark would even jump to a screwdriver tip. Someone had replaced the plug wires with copper wires. After replacing those with OEM suppression wires, the jumping spark at coil+ and the module failures both disappeared. I did not take this as coincidence, but I took it as the secondary clearly affecting the primary. Do you believe that was a valid conclusion? Is that what you are saying in your second to last paragraph? And would you have any clearer explanation?
Thanks again,
Tom
Last edited by tommd; Oct 10, 2022 at 10:02 PM.
Thread Starter
Tech Contributor
Joined: Jun 2004
Posts: 20,913
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
thanks for the response. Obviously, i have some follow up questions!
1. " true for a transformer,but remember the coil, with its secondary open..."
yes, i can follow the opens you mention. I was more concerned about the points opening and assumed the condenser in the primary would pass the varying current. Okay. If i look at an oscilloscope showing the secondary, it graphs the voltage. That voltage, in the early portion of the trace builds to a high level. No current flow yet. Then the current flows and the spark jumps. So to be clear, then the rest of the trace showing the voltage swinging up and down has no current flow associated with it? Yes and No. There's two scenarios that will give you that waveform. One is with a points setup where the coil inductance and the condenser capacitance form an oscillator, which will give you the waveform you describe. It looks neat on a 'scope, but there's energy loss every time the coil output voltage switches polarity in those swings. The second scenario is when swirl/turbulence in the cylinder blows the plug arc out under some conditions. In both situations, if the coil still has sufficient energy in it (the magnetic field hasn't entirely diminished) the collapsing field will build up the secondary voltage (again) and try to initiate another plug gap arc. Depending on how much energy is in the coil initially, and how much the oscillation or swirl tries to extinguish the arc, it's possible that there may be multiple secondary voltage/current peaks and valleys.
so, if the spark required is high energy, i assume that high energy is supplied by high electrical usage. Yes. if the spark required is low energy, i assume the electricity usage is low. Yes, if the engine does not need a lot of energy to initiate combustion, then the manufacturer would design or select an ignition setup that supplies only a modest amount of energy to the plugs. so if sometimes we use more energy, sometimes less to create the spark, and the coil primary input is fairly constant then it must always be drawing enough to meet the maximum energy needed? Correct. what happens to the maximum drawn by the primary when the secondary does not need maximum? (not sure i am being clear???) You're clear. The simple answer is that in that scenario an excess of spark energy will be delivered to the plug gap. Not a big concern. If the plug doesn't need much energy at the moment, it's almost always because there's a light load on the engine (and attending lower cylinder pressures). Lower cylinder pressures reduce the flyback voltages that the primary and secondary windings are subjected to, reducing the stress on the coil insulation/dielectric. The coil output current duration will be increased a bit, as it takes longer to "empty" the coil under lower secondary voltage conditions. (Energy = voltage x current x time. For a constant energy amount, if you reduce the voltage then the time/duration must go up to make both sides of the equation match.)
2. Then i have trouble following- sorry. You first say they can and will affect each other. Then you seem to say it is minimal. Then i hear they are separate, but when the spark fires the flyback is reflected in the primary?? I am sure it is me, but could you be more specific? Yes. During primary current dwell time the coil is "charging" up. There is a magnetic field being built up in the coil. This building field surrounds both the primary and secondary windings. When the dwell stops (when the points open), the magnetic field collapses. The field collapse induces a rising voltage in both the secondary and the primary windings. When one of the sides finally initiates an arc (which will be the secondary on a properly working system, and the primary on a points system with a defective condenser), the rising voltages stop climbing. A typical/normal situation might be 20,000V on the secondary, and 200 V on the primary (with a typical 100:1 turns ratio coil).
3. Part of the reason this had come up in my mind years ago was with a problem with repeated nipon denso distributor module failures. The modules were failing every few weeks. The initial assumption was too high primary current- and one possible cause too high alternator voltage. In checking the voltage at the coil + post, i noticed a spark jumping to my voltmeter lead, something i did not expect with 14volts. I also noticed the spark would even jump to a screwdriver tip. Someone had replaced the plug wires with copper wires. After replacing those with oem suppression wires, the jumping spark at coil+ and the module failures both disappeared. I did not take this as coincidence, but i took it as the secondary clearly affecting the primary. Do you believe that was a valid conclusion? Is that what you are saying in your second to last paragraph? And would you have any clearer explanation?
Thanks again,
tom
1. " true for a transformer,but remember the coil, with its secondary open..."
yes, i can follow the opens you mention. I was more concerned about the points opening and assumed the condenser in the primary would pass the varying current. Okay. If i look at an oscilloscope showing the secondary, it graphs the voltage. That voltage, in the early portion of the trace builds to a high level. No current flow yet. Then the current flows and the spark jumps. So to be clear, then the rest of the trace showing the voltage swinging up and down has no current flow associated with it? Yes and No. There's two scenarios that will give you that waveform. One is with a points setup where the coil inductance and the condenser capacitance form an oscillator, which will give you the waveform you describe. It looks neat on a 'scope, but there's energy loss every time the coil output voltage switches polarity in those swings. The second scenario is when swirl/turbulence in the cylinder blows the plug arc out under some conditions. In both situations, if the coil still has sufficient energy in it (the magnetic field hasn't entirely diminished) the collapsing field will build up the secondary voltage (again) and try to initiate another plug gap arc. Depending on how much energy is in the coil initially, and how much the oscillation or swirl tries to extinguish the arc, it's possible that there may be multiple secondary voltage/current peaks and valleys.
so, if the spark required is high energy, i assume that high energy is supplied by high electrical usage. Yes. if the spark required is low energy, i assume the electricity usage is low. Yes, if the engine does not need a lot of energy to initiate combustion, then the manufacturer would design or select an ignition setup that supplies only a modest amount of energy to the plugs. so if sometimes we use more energy, sometimes less to create the spark, and the coil primary input is fairly constant then it must always be drawing enough to meet the maximum energy needed? Correct. what happens to the maximum drawn by the primary when the secondary does not need maximum? (not sure i am being clear???) You're clear. The simple answer is that in that scenario an excess of spark energy will be delivered to the plug gap. Not a big concern. If the plug doesn't need much energy at the moment, it's almost always because there's a light load on the engine (and attending lower cylinder pressures). Lower cylinder pressures reduce the flyback voltages that the primary and secondary windings are subjected to, reducing the stress on the coil insulation/dielectric. The coil output current duration will be increased a bit, as it takes longer to "empty" the coil under lower secondary voltage conditions. (Energy = voltage x current x time. For a constant energy amount, if you reduce the voltage then the time/duration must go up to make both sides of the equation match.)
2. Then i have trouble following- sorry. You first say they can and will affect each other. Then you seem to say it is minimal. Then i hear they are separate, but when the spark fires the flyback is reflected in the primary?? I am sure it is me, but could you be more specific? Yes. During primary current dwell time the coil is "charging" up. There is a magnetic field being built up in the coil. This building field surrounds both the primary and secondary windings. When the dwell stops (when the points open), the magnetic field collapses. The field collapse induces a rising voltage in both the secondary and the primary windings. When one of the sides finally initiates an arc (which will be the secondary on a properly working system, and the primary on a points system with a defective condenser), the rising voltages stop climbing. A typical/normal situation might be 20,000V on the secondary, and 200 V on the primary (with a typical 100:1 turns ratio coil).
3. Part of the reason this had come up in my mind years ago was with a problem with repeated nipon denso distributor module failures. The modules were failing every few weeks. The initial assumption was too high primary current- and one possible cause too high alternator voltage. In checking the voltage at the coil + post, i noticed a spark jumping to my voltmeter lead, something i did not expect with 14volts. I also noticed the spark would even jump to a screwdriver tip. Someone had replaced the plug wires with copper wires. After replacing those with oem suppression wires, the jumping spark at coil+ and the module failures both disappeared. I did not take this as coincidence, but i took it as the secondary clearly affecting the primary. Do you believe that was a valid conclusion? Is that what you are saying in your second to last paragraph? And would you have any clearer explanation?
Thanks again,
tom
I'll just have to ask you to let me mull this over for a while. I will admit it's a curious scenario.
7th Gear
Joined: May 2019
Posts: 7
Likes: 0
Yes, I would be interested in any further thoughts you might have on the HT wires and modules failing. Per my memory, we had the same problem with several Pertronix Ignitor modules. They would fail repeatedly until we switched to resistor wires. Coincidence? Guess it could have been, but it did not seem so.
thanks,
Tom
thanks,
Tom
