Diode across coil?

[MrTube]

Hey,

Sorry, long time no post!

Is there any reason we can't or shouldn't use a large diode across the coil instead of a capacitor across the points?


If the capacitor is there merely to keep the points from burning I would think a diode could do a far better job and take up less room and last a whole lot longer as well as being easier to hide.

Sourcing quality parts would also not be a problem as it is with the capacitors.

[Mike V. Florida]

Originally Posted by MrTube

Hey,

Sorry, long time no post!

Is there any reason we can't or shouldn't use a large diode across the coil instead of a capacitor across the points?


If the capacitor is there merely to keep the points from burning I would think a diode could do a far better job and take up less room and last a whole lot longer as well as being easier to hide.

Sourcing quality parts would also not be a problem as it is with the capacitors.

There is the problem, the cap also discharges into the coil adding to the efficiency of the coil.

[MrTube]

Originally Posted by Mike V. Florida

There is the problem, the cap also discharges into the coil adding to the efficiency of the coil.

How does it do that?
When the points are closed the capacitor has both ends connected to ground. When the points are open the coil discharges and while the cap charges at this point it gets discharged as soon as the points close?

I cannot see the capacitor effecting the output of the coil at all but I may be missing something.

[newshirt]

A helpful description from Les Andrews, Model A Ford Troubleshooting & Diagnostics (blue book), page 4-3

Points and condenser: The distributor points are made of tungsten to reduce the transfer of metal from one contact to the other caused by arcing. When the points open, the ignition primary circuit is interrupted. But the flow of current cannot be stopped instantaneously. The current continues to flow and arc across the points. To stop this flow, a condenser is connected across the points so that when the points start to open, the current surges into the condenser. By the time the condenser is fully charged, the points are open wide enough to prevent an arc and the current flow stops and the magnetic field in the coil collapses quickly. The speed of collapse is aided by the discharge of the condenser back through the coil primary windings in reverse direction.Therefore, the purpose of the condenser is to reduce arching at the points, thereby increasing point life, and to speed up the collapse of the magnetic field of the coil.

[Mike V. Florida]

Thanks newshirt and 1930coupe.

[Purdy Swoft]

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[QUOTE=MrTube;935064]Hey,

Sorry, long time no post!

Is there any reason we can't or shouldn't use a large diode across the coil instead of a capacitor across the points?


If the capacitor is there merely to keep the points from burning I would think a diode could do a far better job and take up less room and last a whole lot longer as well as being easier to hide.

Sourcing quality parts would also not be a problem as it is with the capacitors.[/QUOTE

You may be on to something good !!! I've got an open mind. I admit that I know next to nothing about diodes. My only experience with diodes is installing the ones that Brattons and Snyders sell to be installed in old cutout shells. My experience with diods in old cutouts have been excellent and never a problem. Still some say that they can't work because of heat, this hasn't been a problem for me. You seem to be pretty sharp on electrical stuff. I have no idea of how to try a diode in place of the condenser. You should try it and tell us how it works and how to do it . I have people telling me that hooking the condenser to the coil won't work, even after I have done it for over eight years and have shown pictures of the set up.

[MrTube]

[QUOTE=Purdy Swoft;935103]

Originally Posted by MrTube

Hey,

Sorry, long time no post!

Is there any reason we can't or shouldn't use a large diode across the coil instead of a capacitor across the points?


If the capacitor is there merely to keep the points from burning I would think a diode could do a far better job and take up less room and last a whole lot longer as well as being easier to hide.

Sourcing quality parts would also not be a problem as it is with the capacitors.[/QUOTE

You may be on to something good !!! I've got an open mind. I admit that I know next to nothing about diodes. My only experience with diodes is installing the ones that Brattons and Snyders sell to be installed in old cutout shells. My experience with diods in old cutouts have been excellent and never a problem. Still some say that they can't work because of heat, this hasn't been a problem for me. You seem to be pretty sharp on electrical stuff. I have no idea of how to try a diode in place of the condenser. You should try it and tell us how it works and how to do it . I have people telling me that hooking the condenser to the coil won't work, even after I have done it for over eight years and have shown pictures of the set up.

This is my thought.
The diode would not conduct while the points are closed, but in theory would conduct when the points open to protect the points.

It seems, according to others this is not the only purpose of the capacitor though.

[newshirt]

Originally Posted by MrTube

The diode would not conduct while the points are closed, but in theory would conduct when the points open to protect the points.

My guess... as soon as the points open, the coil's primary winding is shunted by the diode. The primary field never collapses. No voltage is developed in the secondary.

[Kurt in NJ]

If you use theA&L condenser you won't have any condenser problems, I have cooked mine hot enough to melt solder---- and it is still good , so far 25 years of abuse

[MrTube]

Originally Posted by newshirt

My guess... as soon as the points open, the coil's primary winding is shunted by the diode. The primary field never collapses. No voltage is developed in the secondary.

I'm curious how modern ignition systems work? But I can't seem to find a schematic anywhere.

It's very possible you are 100% right.

[Tom Wesenberg]

It won't work because about 5 years ago I tried it just to demonstrate that the condenser has a dual purpose. I also tried a light bulb in place of the condenser. Both the light bulb and diode kept the points from arcing, but they also kept the secondary windings from developing the high voltage needed to fire the plug.

[Kevin in NJ]

Modern ignition circuits likely use some low resistance mosfets to turn on the coils.

The reason why a condensor at the coil is bad is because there is resistance in the wires and it will cause some arcing at the points. Is you have any marginal connection you increase the chance of the engine not quite working right or damage to the points. Keep in mind you may not see any problems, but that does not mean they are not there. Since you do not drive a lot then you may not see a real problem at the points.

The fact is you are best to use the A&L condensor in the dist as they use a very high quality capacitor that can handle the heat and last for decades.

Quite frankly. Given the wide body of positve results I think one would unwise to not use the A&L units since they are so stinking cheap and they just work.

[MrTube]

Originally Posted by Tom Wesenberg

It won't work because about 5 years ago I tried it just to demonstrate that the condenser has a dual purpose. I also tried a light bulb in place of the condenser. Both the light bulb and diode kept the points from arcing, but they also kept the secondary windings from developing the high voltage needed to fire the plug.

Interesting!

Originally Posted by Kevin in NJ

Modern ignition circuits likely use some low resistance mosfets to turn on the coils.

Wouldn't you still need the capacitor if it does indeed have a dual purpose? I would also expect the coil to fry any mosfets without some sort of protection same as the points no?

[Pete]

Originally Posted by MrTube

I'm curious how modern ignition systems work? But I can't seem to find a schematic anywhere.

I did a simple search for "Ignition coil resonance" and found enough reading material to last for several days.

[tbirdtbird]

U gotta have a capacitator. Just ask Charlie Kettering who invented the L-C circuit we know as the ignition circuit. That it keeps the points from burning is true but irrelevant and overrated. A "myth" to hang onto since none of us other than Charlie understands what the hell an L-C circuit does

Once Charlie did that he put the magneto boys out of business.

U don't have to mount the capacitator inside the dizzy if U don't want to. It can be anywhere. I have slapped a spare one on the firewall when I was caught short and in a hurry. Just as long as it is on the points side of the coil it will work fine, and could be in Arkansas and would still work

I know ppl who have put it on the firewall deliberately to keep heat away from it

[Patrick L.]

That extra couple feet of wire means nothing to a condenser/capacitor installed on the firewall. Electrons are pretty quick little critters. They get where want to go in less than a nano-second.
All I can say is, if you think a diode will work in place of the condenser then try it and post the results. I'd recommend having an extra condenser and set of points on hand for when you decide to drive the car somewhere though.
Plus I think about the only folks that can understand this are Charles Kettering or Nickola Tesla.

[jmeckel]

Originally Posted by 1930 coupe

NO IT WILL NOT WORK!!
A diode and a capacitor are completely different animals and not interchangeable.
The capacitor does more than prevent arcing at the points, it also forms a L-C resonant circuit to boost the voltage. If you remove the capacitor your engine will die or run very bad.
The L-C osculations also make the spark last longer.

http://en.wikipedia.org/wiki/LC_circuit

This is correct, if you do not understand electronic theory, trust us that have had to learn it in depth and can do this type of circuit design in our sleep, the capacator is needed for the LC circuit, that is its primary purpose, the fact that it helps reduce point arc is a secondary benefit. A diode in this particular LC circuit will not work. There are LC circuits that use for example, a PIN Diode, but those are in high frequency RF systems, not automotive ignition systems.

[marc hildebrant]

As others have noted, the cap is used to both reduce the arc and to boost the coil voltage. It's a L-C circuit and it's invention was a great step forward for good ignition systems.

In order to understand the operation, you need to study L-C circuits.

Diodes are used often as "snubbers" with relays in order to stop the sparking, but it's not the same as an ignition coil.

Marc

[Pete]

"A "myth" to hang onto since none of us other than Charlie understands what the hell an L-C circuit does."

Speak for yourself.

"Once Charlie did that he put the magneto boys out of business."


A magneto needs a capacitor just like a battery ignition.

[Chuck Sea/Tac]

Originally Posted by 1930 coupe

NO IT WILL NOT WORK!!
A diode and a capacitor are completely different animals and not interchangeable.
The capacitor does more than prevent arcing at the points, it also forms a L-C resonant circuit to boost the voltage. If you remove the capacitor your engine will die or run very bad.
The L-C osculations also make the spark last longer.

http://en.wikipedia.org/wiki/LC_circuit

Interestingly enough, there is an animal called a quench arc, that is a combination of a diode and a capacitor. Not for cars tho, but to stop a collapsing field from tripping a gfi.

[tbirdtbird]

Pete, maybe a magneto does need a cap. Won't argue. But I have worked on a lot of early mags like from 1910 and if there was a cap it sure was hidden away.....

[tbirdtbird]

I'm sure of it. Maybe one of them can give a quick synopsis that the rest of us can understand

[Tom Wesenberg]

IGNITION WITHOUT A CAPACITOR

Some of the old hit and miss engines used what was known as low tension ignition. The contact points are inside the combustion chamber and connected to a 6 volt battery and coil wired in series. When the points open a spark is created by the coil's collapsing field, and this fires the gas mixture. In this case you want a big spark across the points, so no condeser is used.

[Mike V. Florida]

Originally Posted by Tom Wesenberg

IGNITION WITHOUT A CAPACITOR

Some of the old hit and miss engines used what was known as low tension ignition. The contact points are inside the combustion chamber and connected to a 6 volt battery and coil wired in series. When the points open a spark is created by the coil's collapsing field, and this fires the gas mixture. In this case you want a big spark across the points, so no condeser is used.

Also see Wright Bros. first engine.

[MrTube]

Interesting replies from some.

Thank you all for responding. I do have an electronics backround and do understand LC circuits.

I was talking with an electrical engineer where I work about this and his opinion was the capacitor was needed but he wasn't 100% sure and my opinion was it was there only to prevent burning of the points. We primarily work with RF here in the 2.4 - 5.8 GHz range.


Looks like he was right and I was wrong.

[MrTube]

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Originally Posted by tbirdtbird

I'm sure of it. Maybe one of them can give a quick synopsis that the rest of us can understand

This may help.

http://youtu.be/6qrOoes_At8

[MrTube]

Originally Posted by Patrick L.

That extra couple feet of wire means nothing to a condenser/capacitor installed on the firewall. Electrons are pretty quick little critters. They get where want to go in less than a nano-second.
All I can say is, if you think a diode will work in place of the condenser then try it and post the results. I'd recommend having an extra condenser and set of points on hand for when you decide to drive the car somewhere though.
Plus I think about the only folks that can understand this are Charles Kettering or Nickola Tesla.

Not sure if I can agree with that statement at least not in general. Very often a fraction of an inch effects how a circuit performs.

Those squiggly lines on the PCB are most likely for timing. If you open up a PC you will find this all over. They are referred to as meanders

[tbirdtbird]

Not that critical in this case. I have run caps on the firewall in an emergency in several cars just to get going quickly

[Purdy Swoft]

Originally Posted by tbirdtbird

Not that critical in this case. I have run caps on the firewall in an emergency in several cars just to get going quickly

I agree !!! Some of the older guys did it all the time. I've had one of mine set up this way for years just for the hell of it because I( knew that I could. I didn't do it because I thought that I had to or because I thought it was the best way to go. I was shown this setup back around 1960-61 and always considered it a novelty. I probably won't be driving the car that I have setup that way to Cali-phone-ya to see Bill but it has worked for many years on my sept 29. I run the A&L condensers in the rest of my model A's except the two that run Mallory distributors.

[tbirdtbird]

http://youtu.be/6qrOoes_At8

ha ha this is a joke right

My dog ate my slide rule and i could make no sense of it.

Someone who understands it so well that they don't need equations to explain it might be able to step up and enlighten us

"You might want to click on some of the posters profiles before making a statement like that. Many of the posters have a electronic background and can quote L-C formulas in there sleep. "

My point was missed. Formulas are for engineers. For the rest of us a simple verbal explanation would do wonders.

[Purdy Swoft]

Being a common man, BS credentials never meant much to me.

[MrTube]

Originally Posted by tbirdtbird

http://youtu.be/6qrOoes_At8

ha ha this is a joke right

My dog ate my slide rule and i could make no sense of it.

Someone who understands it so well that they don't need equations to explain it might be able to step up and enlighten us

"You might want to click on some of the posters profiles before making a statement like that. Many of the posters have a electronic background and can quote L-C formulas in there sleep. "

My point was missed. Formulas are for engineers. For the rest of us a simple verbal explanation would do wonders.

No need to be sarcastic.

How about this one.

http://youtu.be/hqhV50852jA

[Mike V. Florida]

Originally Posted by MrTube

Interesting replies from some.

Thank you all for responding. I do have an electronics backround and do understand LC circuits.

I was talking with an electrical engineer where I work about this and his opinion was the capacitor was needed but he wasn't 100% sure and my opinion was it was there only to prevent burning of the points. We primarily work with RF here in the 2.4 - 5.8 GHz range.


Looks like he was right and I was wrong.

You weren't wrong you did not have the whole story.

I spend many years at Comsat in CT., Directv latin america in Fl, in the uplink centers. C,L,KU bands.

[dlfrisch]

For a lot of years, I taught electrical trades - theory and electrical construction. L = symbol for induction and C= symbol for capacitance (LC). A quickie.... we used to use capacitors across some traffic light controller points to protect them from to much arcing and opening that special circuit. We did use diodes because we didn't need or rely on any residue currents. Like most of us - they are older controllers and not too may around yet. Most systems are solid-state and real reliable. (glad I'm retired and play with my Harley and my "A" now! )
As per Wikipedia -
An inductor-capacitor circuit (LC circuit) is an electric circuit composed of inductors and capacitors. A second order LC circuit is composed of one inductor and one capacitor and is the simplest type of LC circuit.
A second order LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, consists of an inductor, represented by the letter L, and a capacitor, represented by the letter C. The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuit's resonant frequency.
LC circuits are used either for generating signals at a particular frequency, or picking out a signal at a particular frequency from a more complex signal. They are key components in many electronic devices, particularly radio equipment, used in circuits such as oscillators, filters, tuners and frequency mixers.
An LC circuit is an idealized model since it assumes there is no dissipation of energy due to resistance. Any practical implementation of an LC circuit will always include loss resulting from small but non-zero resistance within the components and connecting wires. The purpose of an LC circuit is usually to oscillate with minimal damping, so the resistance is made as low as possible. While no practical circuit is without losses, it is nonetheless instructive to study this ideal form of the circuit to gain understanding and physical intuition. For a circuit model incorporating resistance, see RLC circuit.

[PC/SR]

Ok,I'll try a very cursory and much simplified explanation:
When the points open, current continues to flow into the condensor (The "C")until it is fully charged. Because of the component design and matching of the condensor and the coil (the "L") the current oscillates back and forth at the speed of light until the voltage in the primary circuit builds up to about 4-500 volts. This voltage is sufficient to induce enough voltage out of the secondary to jump the spark gap, say 7-10,000 volts.
Why the voltage builds up from the original 12 volts has to do with the properties of electricity in a tuned, resonant (LC) circuit (essentially a short circuit) which allows voltage buildup, and the extraction of energy from the magnetic field of the coil. Try this link. http://www.fas.harvard.edu/~scphys/c...E1b/E1b_3b.pdf

[hardtimes]

I do not have a degree in electronics, and think that most here do not either. So, with my little understanding of DC auto type electricity, I like pictures to help with my meager second order LC circuit understanding. If you have ever observed an oscillascope connected to a running auto electrical system, the 'picture' given of this LC circuit in action....really helps to understand some of what's said here. Do not know if this old machine even applies to current(ha..yeah intended,eh) auto systems...even tho they are still DC electricity ?
And, if you've never heard of and/or seen one of these old auto analytical machines in action, I recommend it. For those with often asked question...such as, how do I determine what is going/gone wrong (if anything) with my ignition system,i.e.-condenser, points,coil/ spark plugs, etc..., get a guy who has an scope, have him hook it to your A / whatever old car with pts/plugs/cond, and have him explain what it is that you're seeing.
Pictures are good for lighting up and completing YOUR circuit !!
Oh, btw, it will show you why / how condenser functions as a NECESSARY part of this system.

[hoop98]

Electronic Ignitions don't seem to need the capacitor across the transistor when it opens. ?



The backward diode will reverse conduct and clip the primary voltage at 600 to protect the circuit.

[emf]

Points need a capacitor, in part, because the switch (points) is mechanical and the capacitor helps reduce metal migration. The mosfet circuit above is solid state with no moving parts, hence no metal migration...

Frank

[hoop98]

Originally Posted by emf

Points need a capacitor, in part, because the switch (points) is mechanical and the capacitor helps reduce metal migration. The mosfet circuit above is solid state with no moving parts, hence no metal migration...

Frank

More than metal migration, you won't get a high voltage spark without the cap/cond. You will get a spark across the points. If you look at a grounded plug outside the combustion chamber you will see a weak yellow spark with no snap. With the condenser you will see a snappy blue spark.

Proper sizing of the condenser reduces metal migration, too much or too little capacitance will change which point gets the buildup.

[Mike V. Florida]

Originally Posted by hoop98

Electronic Ignitions don't seem to need the capacitor across the transistor when it opens. ?



The backward diode will reverse conduct and clip the primary voltage at 600 to protect the circuit.

The schematic is not meant for use in a car

[MrTube]

See this is what I don't understand and is what spawned this conversation.
Why doesn't a solid state ignition need a capacitor in series with the coil if it is indeed an tank circuit?

If it is a tank circuit the cap would be needed no matter what the switching device is, no? Unless of course modern coils have a cap built in which I suppose is possible but I'd expect it to be listed on schematics then as well.

[marc hildebrant]

MrTube.....

Lets try another approach :

1. When the points close, the current in the coil's primary creates a large magnetic field.

2. When the points open, this magnetic field collapses since their is no current to keep it present.

3. When a magnetic field collapses, the changing amount of magnetic field creates a current in the secondary and because the number of turns of wire is large, a large voltage is produced in the secondary. The amount of voltage is related to the rate that the field collapses and the number of turns of wire...so you want a fast collapsing field.

4. When the points open, the current that was going into the coil from the battery wants to continue to flow...this is called inductance. Since the current tries to keep flowing when the points open, a spark will form which is the current trying to keep flowing.

5. The resulting spark at the points is wasted energy that could have been in the collapsing field, thus the spark at the spark plug is weak.

6. If a cap is placed at the points, then the current that was trying to flow by jumping across the points is diverted into the cap. After a very short time, the energy in the cap flows back out into the coil and boosts the collapsing field, thus increasing the spark at the spark plug.

7. Moving the cap from the points changes this flow of energy from the points to the cap and back to the coil.

8. It's not really a "tuned circuit" in the RF sense, but it's like a tuned circuit.

9. If a diode is uses instead of a cap, then when the points open, the energy from the current trying to keep flowing (inductance) will flow into the diode and become heat and you will have a poorer spark than you would have with a cap.

Marc

[MrTube]

Originally Posted by marc hildebrant

MrTube.....

Lets try another approach :

1. When the points close, the current in the coil's primary creates a large magnetic field.

2. When the points open, this magnetic field collapses since their is no current to keep it present.

3. When a magnetic field collapses, the changing amount of magnetic field creates a current in the secondary and because the number of turns of wire is large, a large voltage is produced in the secondary. The amount of voltage is related to the rate that the field collapses and the number of turns of wire...so you want a fast collapsing field.

4. When the points open, the current that was going into the coil from the battery wants to continue to flow...this is called inductance. Since the current tries to keep flowing when the points open, a spark will form which is the current trying to keep flowing.

5. The resulting spark at the points is wasted energy that could have been in the collapsing field, thus the spark at the spark plug is weak.

6. If a cap is placed at the points, then the current that was trying to flow by jumping across the points is diverted into the cap. After a very short time, the energy in the cap flows back out into the coil and boosts the collapsing field, thus increasing the spark at the spark plug.

7. Moving the cap from the points changes this flow of energy from the points to the cap and back to the coil.

8. It's not really a "tuned circuit" in the RF sense, but it's like a tuned circuit.

9. If a diode is uses instead of a cap, then when the points open, the energy from the current trying to keep flowing (inductance) will flow into the diode and become heat and you will have a poorer spark than you would have with a cap.

Marc

Hi Marc,

I'm understanding that part.
Now I'm confused as to why it looks like modern ignitions do not have a cap in that section of the circuit.

Perhaps either it's built into the coil and we aren't seeing it, or the schematics are wrong?

Or, maybe the coils just have far more turns and the switching device can handle a lot more current than points?

[MikeK]

Originally Posted by MrTube

See this is what I don't understand and is what spawned this conversation.
Why doesn't a solid state ignition need a capacitor in series with the coil if it is indeed an tank circuit? . . .

The answer is the waveform from a transistor switch is a very fast and sharp fall, and a mechanical switch that arcs on opening produces a slower, ramped fall. Since the secondary high voltage spark is generated from the rapid FALL or collapse of the coil's magnetic field a simple mechanical switch will not provide this. The widening arc as the points open do not allow a fast enough mag field movement to produce the required secondary voltage. The L-C is actually an 'after the fact' event that produces the necessary rapid waveform transition for a high voltage with mechanical points.

A solid state system without L-C produces a much shorter duration spark, as there is no coil current resonance after the initial mag field collapse. Most transistor switched ignitions do not employ the capacitor because a discharged cap would momentarily present itself as a direct current short when the transistor switches 'on' (points close). The instantaneous initial high current surge into the cap would damage the transistor junction.

[MrTube]

Originally Posted by MikeK

The answer is the waveform from a transistor switch is a very fast and sharp fall, and a mechanical switch that arcs on opening produces a slower, ramped fall. Since the secondary high voltage spark is generated from the rapid FALL or collapse of the coil's magnetic field a simple mechanical switch will not provide this. The widening arc as the points open do not allow a fast enough mag field movement to produce the required secondary voltage. The L-C is actually an 'after the fact' event that produces the necessary rapid waveform transition for a high voltage with mechanical points.

A solid state system without L-C produces a much shorter duration spark, as there is no coil current resonance after the initial mag field collapse. Most transistor switched ignitions do not employ the capacitor because a discharged cap would momentarily present itself as a direct current short when the transistor switches 'on' (points close). The instantaneous initial high current surge into the cap would damage the transistor junction.

Ah!

I wish this forum had a "like" button cause that was a perfect explanation.

Thanks Mike!

[hoop98]

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Originally Posted by Mike V. Florida

The schematic is not meant for use in a car

Here is the block diagram of a HEI IC.




Bottom line is that with a mechanical switch on a Kettering ignition you need the condenser (capacitor) to allow the points to get far enough open to prevent arcing as the primary voltage rises to ~150 volts. Introducing this capacitor does effect the circuit but is only required due to the contacts needing a head start.

With an electronic switch no capacitor is typically used.

I wonder if Charles's experience at NCR on electric typewriters might have inspired his ignition. He would have faced the challenge of despiking the solenoids that did the typing work?

[MikeK]

Originally Posted by hoop98

. . . I wonder if Charles's experience at NCR on electric typewriters might have inspired his ignition. He would have faced the challenge of despiking the solenoids that did the typing work?

I think you're on to something! Likely a shocking unexpected discovery. Kettering, of course, pre-dates diodes by over 30 years.

Wow, that schematic shows how things have progressed. 1996 tech and a Darlington output! Today the coil drivers are all MOSFET.

[johnbuckley]

Originally Posted by MrTube

Not sure if I can agree with that statement at least not in general. Very often a fraction of an inch effects how a circuit performs.

.
I've run my As with the capacitor on the firewall for decades. Electronic/magnetic fields move at very approx 1/10 speed of light . work the maths out for a couple of extra feet of wiring if you're so inclined. ( Ditto HT leads from plugs to distributor!)

[MrTube]

Originally Posted by johnbuckley

.
I've run my As with the capacitor on the firewall for decades. Electronic/magnetic fields move at very approx 1/10 speed of light . work the maths out for a couple of extra feet of wiring if you're so inclined. ( Ditto HT leads from plugs to distributor!)

As I said previously it's these kind of assumptions that cannot be made.
Many many electronic circuits even a thousandth of an inch can matter.

No, it probably doesn't matter in this circuit, but just going by what speed things move at isn't something you can base an assumption on. If you add a half inch to one of the traces in your mobile phone there is a good chance it would no longer work, at all.