Question For Spark Plug Gurus

I agree with you, maybe what I wrote wasn't clear. You only get a spark when you exceed the breakdown potential for the gap. The radiated RF is from the high frequency components of the rapid change. I wasn't saying that you have to generate a pulse to break down the gap.

 

Yep, I am an EE by training and spent 8 years at LLNL, all through the Regan Star Wars era. Did some super fun and reasonably crazy things there. I just don't get into those discussions that often so most don't know. When they here EE they think programmer and at that I am at best a hack.

 

Probably going to have to take this off-line and go PM as we derail here a bit. I'm not an EE but physics major working on my doctorate, so I'm also a programming hack, esp with some of the programs needed to compile on, I hate it!

 

Energy is an ambiguous term. I'm not trying to be a hardbutt about this but we need to be specific and accurate as possible so as to not confuse, nothing personal here.

We could say energy storage in very loose terms but to be technically correct it would need to be restated to charges and potentials. we can build or create them, move them about or maintain them -requires constant work-.

taking the coil again, the primary windings are brought up to a specific potential, while this is occurring there is work being done, in this case the core is building a magnetic field. The field does not maintain itself with zero load on the supplied potential. In other words the losses in the core and the self capacitance of the windings & the inductance all use 'energy' or current to build the magnetic field, if there was zero losses then there would be no magnetic field to maintain(incidentally this gets into some very heavy stuff and also FTL research, going back to Steinmetz it would be a rotation of j versor, but I digress) The magnetic field really isn't static it's constantly building then collapsing, in order to keep it fixed at a specific gauss would require a steady flow of current, so hence no storage as by definition charge is moving to maintain the field.

 

An explanation of how energy is stored in an inductor and the formulae to calculate how much energy is stored is here:
Inductor - Wikipedia, the free encyclopedia

 

Ok, look, I'm not going to engage in a battle of semantics, if you wish to view it as stored energy then do so.

Your initial post stated that not only was my information mostly techno-babble but also you made the implication I was basically flat out wrong. I gave you the benefit of explaining exactly where I was incorrect, thinking possibly that it could be a misunderstanding. Apparently not, for what ever reason I get the impression you think I'm wrong no matter how I explain it. John even tried to answer you as well, if I was as you put it "pretty much completely incorrect" I'm sure he would have also corrected me. I won't attempt to speak for John but given his resume I think he knows what he's talking about and I haven't seen anything about my information being either babble or completely incorrect.

I now respectfully ask you to explain your post about me being "pretty much completely incorrect"

 

I'm just coming in here late.........haven't really reviewed the personal / technical arguments that have apparently taken place...and I won't waste my time reading the Wiki page ----- as I went school to learn physics and electro-magnetic behavior instead of reading about it on the internet in my bath robe --- .....but......

I would LOVE for ANYONE to "explain" to me how a non-solid state inductor (which a spark plug and an ignition coil are) is capable of storing any electrical energy. It has zero capacitance and is a continuously conductive element in any design configuration.

Parasitic capacitance is immeasureable (you will not even detect it on a high resolution oscilloscope) and completely irrelevant to operation, with the high signal voltages and the large volume / mass-density of the conductors involved, in an automotive spark plug ---- in solid state components (i.e., inductors), operating on micro-voltages and micro-currents and comprised of miniscule volumes of conductive material, yes some transient effects of parasitic capacitance can be potentially significant and influence performance on some EXTREMELY time-sensitive circuits.

But that is not the case here.

 

The fact that inductors store energy is a basic law of electricity as discovered by Michael Faraday and taught in school. You mention you would love someone to explain it but will not read the Wiki page, which explains it.
Well here is the opening statement of the page:
"An inductor, also called a coil or reactor, is a passive two-terminal electrical component which resists changes in electric current passing through it. It consists of a conductor such as a wire, usually wound into a coil. When a current flows through it, energy is stored temporarily in a magnetic field in the coil. "
If you wish to know how it does this you might need to read the article.

There is really so much reference material on this subject out there there is little point in discussing it here. A few seconds of searching brought this article which is specific to ignition systems:

Ignition Coils Application Note | Documents | McLaren Electronics

Which contains the statement "The working principle of a TSI system is very simple. Voltage is connected to an ignition coil which results in a current flow and magnetic energy storage in the coil. When the current is switched off, the collapse of the magnetic field in the primary coil induces a voltage in the secondary coil. "

 

I already went through this in my second post, item by item.
Essentially the issue is you are making something very simple into something very complex by adding spurious statements which are either dubious or incorrect. Later in the thread trying to prove Faraday was wrong by using a whole lot of fairly random statements rather than simply accept the view of the rest of the world as known for a hundred years or so (ie that inductors store energy).

The OPs question could have been answered in a couple of lines and Ferraripilots reply was the most useful on the entire thread and it should really have ended there.

I am not sure why other people dont pull you up on your posts but I suspect it is out of politeness and the fact most people dont want to argue online. I thought quite hard about that first post but just could not see this go on any longer, simple questions being answered by overly complex and sometimes inaccurate rambling replies. If you are professionally engaged in something as I am (Freelance Electronic Engineer currently designing for BMW) then the temptation to get things right on that particular subject is just too great and overcomes the risk of looking like an argumentative smartass, which I doubtless now appear as. It would be the same for any other profession, Doctors often gripe about non-medical people diagnosing online.

If you want an example of how to write a technical article check out the Mclaren article I just found this morning and linked above. It contains a full explanation of how both types of ignition works. Its concise, there is no babble, no wild theories about waveguides or RF propagation, just the required facts which explain how these very simple systems work.

 

Does it make any difference if you use iridium or platinum plugs in an older ferrari engine which was designed for copper plugs(456 V12) ?

 

No (per NGK):

NGK Spark Plugs

The main benefit of the "exotic" material electrode spark plugs is their anti-fouling characteristic (these materials have higher melting temperatures so they make the electrode physically smaller = it runs at a higher temperature = it stays "cleaner" by better burning off any contaminants, if present). The higher melting temp material also typically gives longer life as previously mentioned in this thread. (There's also some mumbo-jumbo about smaller electrode with corners that stay sharper = the charge density being higher = better -- but haven't yet found a real clear explanation of this that says it really applies in modern automotive ignition systems in a way that I can easily understand -- if someone's got a link, please post.)

Do I think that they are a good value when a Shop reams you for $25 each = no; but, at ~$7 each retail (vs ~$2.50 for the standard electrode plug), I use them.

 

Thanks Steve for your response. Andy.

 

I wanted to reply to your reply to David, This post right here really has me debating bothering with anything further, why?

You have no clue who you are trying to school here, none. I'll accept ignorance, not everyone knows everybody here in the real world. Now whether David responds or not I haven't a clue.

 

Copper has the best conductive qualities albeit with shorter life. I tend to just go with copper if they are available.

 

Not sure where you are coming from here. But, reading Davids post again I notice he is questioning how the coil stores electrical energy. It doesnt as we have already established and nobody stated it does. It does store energy though which is both input and output in electrical form.

 

I'm not an EE, just a lowly physics guy. This is not the first time a debate over 'stored energy' has taken place in this field. Over on the physics groups it's happens fairly enough with first yr students and others new to the field. It becomes a case of language not being accurate enough or misleading, hence why mathematics is it's own language. A very good mentor in our group posted the following yrs ago.

As I've said the confusion is mainly due to semantics. In my opinion, it's incorrect to think of energy as being "stored" as if energy was a tangible thing to store somewhere. The fact is that energy is not matter, so thinking of energy as being "stored" or "contained" would just result in further confusion.

In reality there is no good word to describe the "existence" of energy (maybe the word "has", as in "something has energy," would a be better word since it doesn't evoke a materialistic image)

My technical posts are not always written for the laymen, the OP was directed to a more in depth answer. McLaren's website info is very basic and geared to the laymen otherwise they would isolate themselves from their target group, nothing wrong with it in that venue, but as scientist or professionals in those fields we should be able to differentiate and say "OK, technically this is more accurate". I can't change a century of confusion or laymen reductionism on subjects, and I'm not trying to capture John Q public, I was simply giving a response based on my experience and level of education on the subject.

I fear this may simply become a debate of philosophy.

Oh, and absolutely nowhere have a I tried to prove, state or imply Faraday is wrong.

Many believe that resistance and frequency are not related, or that resistance is unaffected by frequency. however it's not really true and the relationships are extremely complex, but the resistance of even something as simple as a length of wire varies with frequency.

The term 'impedance' is usually used in this context, rather than 'resistance.' The impedance seen by a line driver driving a wire at 1 MHz is different from the impedance seen by a line driver at 1 GHz, for example. The reason? Real wires have some capacitance (and some inductance). A thorough understanding of a real wire also has to include some pretty complicated effects, like the skin effect.

The bottom line, in general, is that resistance of a length of wire goes up with frequency. In other words, a length of wire will attenuate high frequencies much more than it will low frequencies.

Impedance is a generalized term for resistance. Impedance includes reactance (capacitance and inductance), whereas resistance does not.

Capacitance and inductance are represented with complex numbers; resistances are always real, while impedances can be complex. When a specific frequency is given, however, a complex impedance can be evaluated at that frequency, producing a real number. That real number is the resistance of the system as seen by a signal of that frequency. And that is why I state that the DVOM measurement of a plugs resistance isn't going to be very useful against the actual operation of the plug in the circuit.

 

I'd go with silver if feasible, as copper is the inner core with a nickle plating or steel tip. silver also has a short life.

 

Its just fine.
We are not talking about AC here, just relatively low frequency DC pulses. Impedance is not worth worrying about, in this context.

The piece by "Physics Mentor" is spot on. What he is essentially saying is that its a mistake to over analyze things.
The question of ignition is a perfect example of this.
In order to explain how the system works it is necessary to state that the coil stores energy otherwise it would not be an accurate explanation. The fact that the spark occurs after the points have opened, when no further energy is being fed into the coil, means the spark energy is stored in the coil. This is irrefutable.
But going on to try and explain why this is not the case because of what we are defining as energy is fruitless and only serves to confuse people.
Yes the Mclaren explanation is for the layman, thats exactly why I highlighted it as an example of the right level of information to present.

Incidentally I also studied Physics, at Imperial College, London (which has sadly dropped to only 8th best university in the world, gone downhill since I left )

Oh and why on earth would you want silver spark plugs? The resistance difference between copper and silver in a plug would be infinitessimal when added to the total resistance in the system.

 

wow, you physics and EE types make lawyers look like amateur egomaniacs.

So, let me see if I have this right. Nothing stores electricity.

If I'm reading that right, that means that a battery makes electricity, it doesn't STORE it, because energy has no matter?

So, why do we "charge" and "discharge" a battery? Are we in fact simply providing a battery with the ability to produce energy?

Schesh, the explosion you just hear was the battery in my head discharging.

Explanations please??

D

 

Your on the right track. Think of it this way, you can't create or destroy energy. You can only change it's form. Charging a battery induces an elctrochemical reaction, kind of like separating H and O in water. Notice that neither gas has any innate energy but it takes energy to separate them. When you 'discharge' the battery you are causing an elctrochemical reaction with the excess energy being released as electricity. Much like combining H and O (skipping the part about the catalyst) produces water and releases a lot of energy as heat and light.

Kind of esoteric stuff and you won't notice a lot of the effects we were discussing when you are not working with high power systems. Plus there are theoretical models (read perfect models) and there is the real world where you have dozens of other factors that have an effect on the total system.

 

I often think that those of us in the fields of physics and quantum electrodynamics are bit 'off' maybe a little unhinged or nutty. Let's be honest, your mind has to be able to not only think outside the box but work out there too. For many that's a step to far, for the rest of us talking to ourselves and enjoying the conversation we fit right in and wonder about the strange beings who are trapped in the box we also like to peek in at the cat every once in awhile too.

energy is a concept, that means it's not tangible and is really only used as a word to convey a mathematical construct. What we needs to be specifically noted is the type of energy being delt with and in what form.

David a number of posts back highlighted a very good point, passive elements. Passive elements are components that can not generate power on their own. a coil is a passive element, an inductor is simple a coil with a core. that core is where the 'magic' happens. to try and explain it simply, lets start with a coil of wire empty sitting on the table. no one expects that coil to do anything, it won't generate electricity or generate a magnetic field by itself. Now lets place a magnet in the middle of the coil on the table, what happens? well nothing. there is a magnetic field around the magnet but that doesn't seem to do anything either, why?

movement over time, the magnet must move with respect to the coil in order for that magnetic field to generate an electrical field that in turn moves the electrons so that we get varying voltage potentials at either end of the coil. Now was that 'energy' of the magnetic field a stored energy? unless magnets are suddenly moving about on their own accord that field is not storing anything, it simply exists as a field. we have to expend energy in other forms, our body movement for example to move that magnetic field in order to generate the end result. we could just as easily move the coil while keeping the magnet fixed, same result. And that is the key, the magnetic field never moved, the coil moved thru the field and the result was a transfer of energy thru manipulation.

A battery is a bit more complex as it's dealing with electrochemical actions, as John explained nicely.

capacitors are not passive elements, they will maintain a charge which could loosely in my opinion be said to store energy, but that would be an ideal element and no such thing exists as capacitors leak. it doesn't store a magnetic field, it doesn't store an electric field, it simply ideally holds a "charge" or voltage potential. once that potential is put to use, then it converts that charge to another form..

we simply can only move the energy around.

 

Believe it or not I agree with all the above

But its worth in the context of this thread adding the situation of an ignition coil, which works differently to above.
In the above example a permanent magnet is used to convert movement into electrical energy. Nothing is stored.
In an ignition coil the core is soft iron and is not a permanent magnet. It is magnetized by applying current to a coil wound around it.
When the current is broken, the situation becomes similar to the above, but instead of the magnet being moved thus changing the field, the field changes by the core losing its magnetism. So this induces a current back into the coil.
Only one coil is needed to observe this behaviour but in the case of the ignition coil a second coil with a much larger number of turns is added and this (and the first coil) has current induced by the change in the field of the core. Owing to the large number of turns on the secondary coil the induced voltage is high.
So in this case there is energy stored. It is stored by means of a change in the magnetic state of the core. When the core reverts to its original state the energy is fed out by means of the change in magnetic field inducing a current in the coil.

 

so, if energy doesn't exist, then how do you explain e=mc2?

sorry, can't superscript the 2, as I'm not all that good at html code.

But, how can energy be equal to anything if it isn't anything?

I'm not trying to be intentionally obtuse, my one year of physics junior year in High School is failing me now.

Or is it more like we're talking about the potential energy an item can have? In which case, my original question still stands. So, I guess really it is the term 'energy' which causes the problem when you're really talking about electricity, which is tangible, right?

Damn, now I have to take a tylenol.

D

 

you can't isolate the battery from the circuit and then say it's storing energy, the battery supplied the current to generate the magnetic field, once that current was stopped the field collapsed. that collapsing field then etc.... OK however there is still no stored energy it was transformed from the electrochemical action of the battery into a magnetic field in the core. We know the magnetic field is an electromagnet, it consumes power to maintain itself, and that is why there is no storage.