Resistor plugs & resistor wires?

[statsystems]

I had a friend ask a question and I didn't have an answer.


He asked why does he need to run a resistor plug if he is already using resistor wires? I said damn...I don't know.

I've always run non resistor racing plugs with resistor wires on race car stuff. But his is a street/strip deal. He wants to try a non resistor plug with his combination but someone (I believe it was someone at NGK's tech because that what he uses for plugs) told him street cars need a resistor plugs AND resistor wires.


After I thought about it...I said how does an engine know it it's a race engine or a street engine.

Basic 572 BBC with 11:1 compression, 4500 converter, MSD 7AL3, MSD distributor. I can't tell him why or why not to use a resistor plug.


Seems like if you don't have to do it on a race car, why does he need to use them? When are they required? When do you need both resistor plugs and wires?

Thanks in advance.

[Kevin Johnson]

https://books.google.com/books?id=PImqH ... es&f=false

[Circlotron]

NGK told him street cars need a resistor plugs AND resistor wires.

Like someone telling you that you need belt AND braces.
In some cases you just might, but if just one is good enough then your done.
I'd use spiral wound lowish resistance plug wires alone and only move to resistor plugs if that wasn't enough.

[peejay]

I had a friend ask a question and I didn't have an answer.


He asked why does he need to run a resistor plug if he is already using resistor wires? I said damn...I don't know.

I've always run non resistor racing plugs with resistor wires on race car stuff. But his is a street/strip deal. He wants to try a non resistor plug with his combination but someone (I believe it was someone at NGK's tech because that what he uses for plugs) told him street cars need a resistor plugs AND resistor wires.


After I thought about it...I said how does an engine know it it's a race engine or a street engine.

That depends on how much electronics you have in the car and how noisy the ignition system is.

[statsystems]

Three good answers. Thank you.

How do I determine how "noisy" an ignition box is? And this car doesn't have many electronics.

[ProPower engines]

if you run both non resistor plugs and wires with the MSD 7 AL3 box that will put out enough voltage to cause the most common wires to leak high frequency static which will guaranteed make your stereo sound like crap.
the main reason for the resistor stuff is to make better spark at the plug. The system need the resistance to force the voltage to build up till it jumps the wall so to speak and fires the plugs.

In the old days of points they still used a resistor somewhere in the path to the plugs be it in the end of the wire or a
resistor spark plug. Now that said the amount of resistance used in systems back in the day is much much less then today's ign. systems are using. as mentioned the best choice for wires is a carbon /fiberglass core wound with a monel or similar wire to keep it tight.

I have a customer that uses the old style 7mm solid core plug wires on everything he owns cause he has a large spool of it for when he does small engine work but I have tried for 25 years to get him to change but NO DICE. can't teach that old dog anything new

[Belgian1979]

Most issues with electronics are to be found with grounds of systems.

In an ignition system you have (i) high voltage running through the wires that would create emi when that voltage has a route to ground other than that were you want it to go and you have (ii) high voltage discharge via the spark plug to the ground. If you don't do anything to the both of them you run a risk (depends) on interference.

[Schurkey]

the main reason for the resistor stuff is to make better spark at the plug. The system need the resistance to force the voltage to build up till it jumps the wall so to speak and fires the plugs.

Nope. Resistors don't affect voltage unless there's current flow. There's no current flow until the spark gaps (rotor-to-cap, center plug electrode to side plug electrode) are ionized and conductive. By that time, you've already got a spark.

With ordinary "solid core" plug wires and non-resistor plugs, there's a fair amount of amperage in each spark. The amperage sets up a magnetic field in the plug wire, which radiates it like a radio transmitter. (Coil wire, too, when applicable.) THAT'S the static you hear on the radio and on TV when a car with no ignition resistors drives within range. (or on your own radio in the dashboard of the car.)

Adding resistance doesn't change the voltage, but it dramatically reduces current. Less current, less magnetism, less magnetism less radio static. Thus the "TVRS" printing on some plug wires--TeleVision and Radio Suppression

My motorcycle uses solid core wires, but the plastic spark-plug caps have a 5,000 ohm resistor in series. Uses resistor plugs as well.


The carbon button under an in-cap HEI coil and resistor plugs just add additional resistance, reduce current flow more, and thus provide more suppression of the radiated "static" from the ignition system.

Aside from radios and televisions, there's all sorts of electronic devices that can be sensitive to Radio Frequency (RF) interference. This can include automotive computers and "spark boxes", along with home and business electronics that might come within range of a vehicle's ignition RF emissions.

Those helical-wound plug wires that advertise low resistance? They use a different principle to kill RF emission--they're essentially an electrcal inductor. They still kill current flow, and therefore magnetism, and therefore RF interference, but they don't use resistance to do it.
https://en.wikipedia.org/wiki/Inductor

[Belgian1979]

or the wires have a metal core surrounding the spark plug wire that conducts the EMI to ground...(one side)

[user-23911]

It's tied up with impedance matching which gives maximum transfer of energy. Got to match the primary side impedance to the secondary side impedance.
Same theory as transmission lines in electrical engineering.

https://en.wikipedia.org/wiki/Transmission_line

[nitro2]

the main reason for the resistor stuff is to make better spark at the plug. The system need the resistance to force the voltage to build up till it jumps the wall so to speak and fires the plugs.

Nope. Resistors don't affect voltage unless there's current flow. There's no current flow until the spark gaps (rotor-to-cap, center plug electrode to side plug electrode) are ionized and conductive. By that time, you've already got a spark.

Okay.
For these examples its just a nice wire no spark plugs no nothing else.
So for this example we have a lets say an average 1 mm gap. There is no spark yet, and lets say it takes 10kv to jump said gap.
Since the above poster, said resistors don't affect the voltage till there is current flow, here is how its done with no current flow.
So boom here is the voltage, I measure 9 kv and sorry right now that's all my little power supply puts out. Yet I see a voltage, yes there is a nice resistor that is affecting my voltage, it is called air and distance, if that wire was shorted against ground there would be zero voltage measured.
Now if I had a power supply that could send millions of volts to the end of my wire, when it jumped my 1mm gap that we know takes 10kv to do so.
That is what I'd measure for voltage. On my next test I'd open that gap up to many feet that is more resistance of course and then now the voltage would go up to what ever it takes to jump that gap. So your statement that resistors don't affect the voltage unless there is current flow is not correct for these examples.
You would be correct for a simple circuit where you are looking for voltage across the resistor itself.
Adding a resistor is like adding more air gap, it takes more voltage to accomplish the arc. So I'm on the same boat as ProPower engines.
Reduce current flow yes, but not voltage because now it takes more to do the job.

An air gap is an insulator and flows no current until a critical voltage is reached. A resistor will flow current at any voltage even at 1/1000th of a volt a resistor still flows current. Two different beasts.

[statsystems]

Nope. Resistors don't affect voltage unless there's current flow. There's no current flow until the spark gaps (rotor-to-cap, center plug electrode to side plug electrode) are ionized and conductive. By that time, you've already got a spark.

Okay.
For these examples its just a nice wire no spark plugs no nothing else.
So for this example we have a lets say an average 1 mm gap. There is no spark yet, and lets say it takes 10kv to jump said gap.
Since the above poster, said resistors don't affect the voltage till there is current flow, here is how its done with no current flow.
So boom here is the voltage, I measure 9 kv and sorry right now that's all my little power supply puts out. Yet I see a voltage, yes there is a nice resistor that is affecting my voltage, it is called air and distance, if that wire was shorted against ground there would be zero voltage measured.
Now if I had a power supply that could send millions of volts to the end of my wire, when it jumped my 1mm gap that we know takes 10kv to do so.
That is what I'd measure for voltage. On my next test I'd open that gap up to many feet that is more resistance of course and then now the voltage would go up to what ever it takes to jump that gap. So your statement that resistors don't affect the voltage unless there is current flow is not correct for these examples.
You would be correct for a simple circuit where you are looking for voltage across the resistor itself.
Adding a resistor is like adding more air gap, it takes more voltage to accomplish the arc. So I'm on the same boat as ProPower engines.
Reduce current flow yes, but not voltage because now it takes more to do the job.

An air gap is an insulator and flows no current until a critical voltage is reached. A resistor will flow current at any voltage even at 1/1000th of a volt a resistor still flows current. Two different beasts.

nitro2...am I correct in thinking if I have a good set of suppression core wires, I have no need to use a resistor spark plug? This thing has very few electronics. I just don't like the idea of running more resistance in the system than I need.

[nitro2]

Air is an insulator. The more air you put in the gap the more voltage you need to jump the gap. The less air you put in the gap the less voltage you need to jump the gap. If you put enough air in the gap you can't jump it at all, the spark will just come out elsewhere.

Adding a resistor does not change the voltage requirement at all if there were no capacitance effects. A resistor does nothing until there is current, and technically there is no current until the gap is jumped, but in reality there is a little current due to capacitance.

The ignition system does not build voltage to overcome a spark gap AND overcome a resistor (unless there is significant capacitance) before firing the plug, it builds voltage to overcome the spark gap. Pulstar plugs are an example where the resistor does have a significant role because they purposely add a capacitor. On some applications Pulstar plugs work really well.

[MadBill]

...
"The more air you put in the gap the more voltage you need to jump the gap." Air pressure, Why is that?

Because compressed air is a better insulator than atmospheric.

[Circlotron]

I agree some what, but a resistor is a current limiting device, it is like having a water hose squeezed at some point, and to try to get more water out of the hose the pressure (voltage) needs to go up.

That's true, but if the voltage is still rising and the spark has not yet begun then (ignoring capacitive effects mentioned by nitro2) no current has begun to flow so a resistor will have no effect. If the water in the hose has not begun to flow because the end is blocked off then any restriction in the hose will not affect the pressure (voltage) because there is no flow (current). Same as there is no pressure (voltage) drop across a throttle body if there is no airflow (current), even if the throttle (resistor) is 95% closed.