Ignition coil testing

[Keithbaja]

Wellll, I'm not going in to how to test a coil or CDM testing. But, I will ask this. Does anyone here know what year the ABYC & the CFR's (part 33) Think, Coast Guard changed the standards for 12vdc negative to Yellow ?? Worst Marine dosnt have a clue. Also Most marine places that have a BIG sign saying "boat repair"

[zenoahphobic]

I would have thought the compressed air would move the molecules closer together, so letting the spark jump easier.
but that is not the way it works.
I do not fully understand.

Good point.
We are not really talking about “standard” conductivity, where tighter packed electrons enable them to jump from atom to atom easier.
A spark is really ionisation of gases! This process is deliberately initiated to create heat to ignite the air/fuel mixture. (Ionisation is electrical conductivity but is used to create a substantial path of heat)

[99yam40]

Good point.
We are not really talking about “standard” conductivity, where tighter packed electrons enable them to jump from atom to atom easier.
A spark is really ionisation of gases! This process is deliberately initiated to create heat to ignite the air/fuel mixture. (Ionisation is electrical conductivity but is used to create a substantial path of heat)

I understand that, but with the tester we are just talking about compressed air with no fuel involved.
what causes the extra resistance to the voltage to jump thru the molecules when packed tighter together.
maybe I should look up the definition of Ionization

what I found, but still does not explain why higher air pressure would effect it

The Townsend discharge is a good example of the creation of positive ions and free electrons due to ion impact. It is a cascade reaction involving electrons in a region with a sufficiently high electric field in a gaseous medium that can be ionized, such as air. Following an original ionization event, due to such as ionizing radiation, the positive ion drifts towards the cathode, while the free electron drifts towards the anode of the device. If the electric field is strong enough, the free electron gains sufficient energy to liberate a further electron when it next collides with another molecule. The two free electrons then travel towards the anode and gain sufficient energy from the electric field to cause impact ionization when the next collisions occur; and so on. This is effectively a chain reaction of electron generation, and is dependent on the free electrons gaining sufficient energy between collisions to sustain the avalanche.^[3]

Ionization efficiency is the ratio of the number of ions formed to the number of electrons or photons used.^[4][5]


maybe the molecules being closer together does not allow the electrons enough time and space to gain enough energy to keep it going, just a thought I had

[boscoe99]

The presence of air acts as an insulator of sorts.

The higher the air pressure the greater its insulation capability. I too do not have an understanding of the physical properties that cause this.

What little I know about this is that in aircraft that are supercharged for high altitude flight, where the air pressure is lowered, the magnetos are pressurized to prevent arcing within the device.

[boscoe99]

[ausnoelm]

Low air pressure makes spark jump much easier, as that quote explains.

[zenoahphobic]

However going towards a complete vacuum a spark becomes weaker until it will not form.
This is because a spark is a release of energy (a range that includes light). It therefore needs some matter to change its state (and exothermIcally).
One always need heat to produce more heat, that is why original spark plugs where actually candles (still called that in other languages). Of course in modern day we use glow plugs, that are simply conductors or resistors that require an electric current to produce heat, combined with latent heat from compression to cause the air/fuel mixture to instantaneously to combust (jet and piston engines).

[99yam40]

I posted 10 hours ago and quoted a definition of ionization and got flagged, and it still has not been posted up

[zenoahphobic]

Wow you’re brave.
I can’t find anything that anybody can readily understand!

[99yam40]

My post #18 finally showed up

[zenoahphobic]

My post #18 finally showed up

Yeah, got it.
I think your “…not enough time and space to build up energy” theory is correct.
Insulation is merely a term we use to describe non conducting, or resistance to electron flow, so it doesn’t really exist on it’s own.
We simplify things all the time and say here that by compressing air we increase it’s insulating properties and therefore need greater voltage to overcome this resistance.
This however doesn’t answer your question!
You need chemistry and physics to understand (not simple). You start by looking at the strength of the bonds of electrons in oxygen and nitrogen molecules. Ionisation is the “ripping off” electrons. The tighter the molecules are together, so to are the forces holding the electron and all the other components together. It is also these forces that resist compression in liquids and solids.
The ionisation we are talking about is within gases and is quite dramatic; a chain reaction. However one can merely dissolve most compounds in water to “loosen” these electrons. Batteries and electroplating are two common examples.

[panasonic]

I used one of those many moons ago! Blast the plugs, look for good spark and back in the engine! Push it out the door and go flying..