Spark plugs seal

[figgie]

Okay, carbon has a resistivity of 1375 uohm-cm and permeability of 1. Assume 1us rise time then that gives a skin depth of 186 microns. For stranded wire (that is insulated between strands) then the skin depth likely exceeds the strand diameter, in other words it doesn't matter. For solid core or uninsulated multistrand a center conductor larger than ~0.4 mm is pointless (assuming you can actually achieve a 1us rise time).

last i checked 186 microns = 1.86 x 10^-2 or .186 millimeter or not even 1/10th the 10mm thickness in "race wires".

as for rise times

let see

at a mere three thousand RPMs you are looking at a ignition event every 1ms. Somehow I think the rise time is lower than what you think

 

[3p141592654]

Whoops, made an error. 186um is for 10ns rise time. For 1 us the skin depth is 1.87mm. For 1ms it is 59 mm.

So the point would be that unless you have a very fast system (and you won't because the Johnson limit for semiconductor transistors applies so that breakdown scales inversely with speed) then skin depth is not an issue. Also, multistrand makes no difference because they are not litz wires.

By the way, doesn't the 10mm apply to the insulator, not the inner conductor?

 

[jetjock]

I have no dog in this fight but I'm still of the opinion anyone who thinks skin effect applies to secondary ignition is barking up the wrong tree.

3p: what are you, design or process engineering? You sound like a design type.

 

[3p141592654]

Hah, your very astute! :icon_bigg Manager of a high frequency advanced devices group. Our biggest customer is DARPA.

 

[jetjock]

DARPA huh? No kidding. Lol, I'd ask but I know if you told me you'd have to kill me

 

[3p141592654]

ITAR restricted, but not classified.

 

[mickyg]

Jetjock: Does it ground through the air and complete the circuit that way?

 

[Boss302]

why? i want to know please. and brovo on this thread so far. so what your saying is that wit htwo spark plugs connected to the same coil pack the reason why they fire is because they have created a circut so if you take one and put it into another block why does it still fie if the circut has been broken? i'll have to ask my boss cause he's studied physics.

oh cause they aren't grouned to begin with by the head or anythinglike the it's internally grounded. i don't know just spouting out. hey it could happen.:icon_bigg

The 7MGTE uses a distributorless ignition system often called DIS but more correctly called DLI. The plugs are fired together in pairs, once on the compression stroke and again on the exhaust stroke. The firings on the compression stroke are called true firings, while the ones on the exhaust stroke are called waste firings, hence the name "waste spark" used for such systems. Not only do the plugs fire twice as often as usual but they also fire with opposite polarities. I won't bore you with the plasma physics involved but this is one reason platinum or iridium tipped plug electrodes are used.

 

[Boss302]

no comments on whether this is bad or good?

 

[figgie]

why? i want to know please. and brovo on this thread so far. so what your saying is that wit htwo spark plugs connected to the same coil pack the reason why they fire is because they have created a circut so if you take one and put it into another block why does it still fie if the circut has been broken? i'll have to ask my boss cause he's studied physics.

oh cause they aren't grouned to begin with by the head or anythinglike the it's internally grounded. i don't know just spouting out. hey it could happen.:icon_bigg

no

i had a hard time visuallizing this and had the same "image" also

the image you have is

you have the stock OEM dual coils, each one plugged into a spark plug on the same engine block. the you disconnect the spark plug and move it to the other engine and see spark. This is the WRONG image

The iamge that jetlock was trying to convey is, we leave the spark plugs wired to the dual coils but move one spark plug from the one block, WHILE still connected to the ignition coil, to the other block. Both will still produce a spark without the "circuit" being there.

 

[Boss302]

self-grounding? like i said before. and thats originally what i thought he meant the mental pictue that is.