Chip

iTrader: (3)

Ok, so here's my limited understand of how the coil works.

It charges up, then when it sees a ground pulse on the firing side, it sends a spark down the HT lead.


Now, couple of questions.

If the ground stays grounded, what happens then? Im assuming that it will prevent the coil from charging, but will it damage anything?

If the +VE side was to be disconnected, what would be the effect? Now obvioulsy the coil would stop working, but how soon would it do so, would it still pulse on the next couple of cycles till it had run out of stored charge, or would the spark stop happen instantly?


CheeRS in advance

lead_foot

iTrader: (1)

Is this in relation to the misfire in your 3 door?

or the Bee*r rev limiter?

Chip

iTrader: (3)

Nothing to do with the 3 door mate.

Its kind of linked to the BEE*R though

GARETH T

it only discharges to the secondary side (ht) once the ground has been disconnected

GARETH T

it will stay charged, and in the end burn the coil out

it would discharge through the ht

discharge straight away,, once!

Chip

iTrader: (3)

So as soon as the cicuit is broken on the low tension side, by either the ground OR the +VE, it will fire the coil then?

Arse, back to the drawing board then, as I wanted a way to cut it WITHOUT it disharging the coil, but by the sounds of it that wont be possible!

GARETH T

explain more dude

Steven_RW

My thoughts are that it doesnt "charge up"

it just converts one input to another output constantly.

It just HAPPENS that we pulse the earthing or the signal into the coil.

IE if u put in x volts to a coil it creates x times 2 volts and half the amps - regardless. It doesn't need to "charge up"

Its not a capacitor.

RW

GARETH T

its the collapsing of the primary coil that induces an emf into the secondary

GARETH T

if we put a ac voltage into it,,, it would work as you describe! but we dont,,

Chip

iTrader: (3)

Yes of course, and this would still happen if you cut the +VE

Simple when you put it like that!

Chip

iTrader: (3)

Nothing more to explain mate, I simply want to stop the spark event from happening, but WITHOUT discharging the coil as I do so.

So for arguments sake if you had a "kill" switch, that as you turned it, the spark would just end there and then, WITHOUT that one last discharge.

Chip

iTrader: (3)

PS

Stupid thing is I already knew about a cut causing a fire, thats why when you hit the rev limiter on a nitrous car when you have a coilpack you potentially get a massive backfire, cause it can fire at ANY point in the cylce, where as on a distributor system its actually quite limited how far out it can try and fire as the rotor arm has to be next to one of the cylinders ht lead terminals at the time or the spark has nowhere to go at that moment so it cant happen during the intake stroke for example, which is what causes the problem.

GARETH T

whats the problem then,, why dont you just have a switch in parallel with the standard coil firing method (be it a dizzy or ignition amp)

Chip

iTrader: (3)

sorry, should have been clearer, the other thing I dont want is for it to fire when i disconnect it either.

The reason being, those sparks can happen at ANY point in the cycle, not just when you want a spark!

foreigneRS

sounds like you don't need it to not discharge for very long periods at a time (gearchange or rev limit?), so why not wire it such that the supply stays on during that time?

Chip

iTrader: (3)

Thats exactly what im on about doing in the first place

But that still has the problem that when you remove the "block" you will get a fire, at any point in the cycle you happen to be at!

foreigneRS

i get you now, it is important to you when that discharge happens - even if the engine is running properly again. but why? it will either fire a cylinder too early or not at all won't it? wouldn't cause a problem would it?

edit: it's just sinking in now you are running NOS on the inlet plenum somewhere so don't want to ignite that mixture if it fires when an inlet valve is open

Chip

iTrader: (3)

Nitrous makes no difference to that, could still ignite the inlet mixture anyway if it was just fuel and air, in fact the nitrous if anything makes it LESS like to fire in a lot of circumstances, although if it does fire, it will do so more dramatically.

Its not just that that is the issue though, its that when it fires you could be 20 degrees later than the inition curve was set for, and hence cause massive detonation in the engine that cycle!

Chip

iTrader: (3)

Chip

iTrader: (3)

BTTT just in case anyone else has any bright ideas (seems unlikely at this time of night )

ECU Monitor Enthusiast

iTrader: (1)

Chip, cossies rev limits are fuel cut NOT spark cut.


Good explation Gareth

StephenC

trying with this one but cant think of a way with it been HT and not so managable. Thinking about maybe something around the HT lead coming from the coil so that when the feed to the coil is broken and thus transfering to the secondary ready for the next impulse it switches in a burden on the secondary side limiting its path. Cant think what though and not sure it would give the full kill you require.
Only other way would be to ground the HT lead prior to it reaching the spark plugs, when required, but again as nothing is readily available it would be a botch up and a) not work and b) look shit.
hard one, i'll sleep on it and probably wake up none the wiser

Chip

iTrader: (3)

Indeed they are, and if this was even vaguely anything to do with a cossie, which it isnt, that would be relevant

Chip

iTrader: (3)

Im liking the concept actually, i think you are right that it would work, but on the downside, is the fact that you would be introducing more components into the HT side of course, which is never a good thing for spark performance, and no limiter should effect spark strength when not active of course!

ECU Monitor Enthusiast

iTrader: (1)

Chip,

You didnt mention it wasnt LOL

Chip

iTrader: (3)

ECU Monitor Enthusiast

iTrader: (1)

Ah, didnt see that. I am a blind cunt

Too many alcopops tonight

Chip

iTrader: (3)

Ive realised something tonight.

Cutting the -VE or +VE has a subtley different effect to earthing the -VE

BOTH methods introduce a random spark event in the cycle, but cutting them can ONLY introduce it in a way that gives extra RETARD and grounding can only introduce it in a way that gives extra ADVANCE.


So cutting the -VE or +VE is infinitately better than grounding the -VE (which is what the limiter im talking about does I believe, although ive yet to test it)

StephenC

How about not cutting the -ve or +ve but decreasing it slowly
"The current within the electronic ignition example shown sharply rises to 6 Amps, at which point the current is held until the earth circuit is removed. The switching speed can be seen by the angle of the vertical line at the end of the trace, any delay or slow switching will be seen as a sloping line. Any compromise in the switching speed will result in a lower induced voltage."
coil basics

with a view of creating less HT voltage that is not strong enough to jump the electrode gap

Chip

iTrader: (3)

Simon, can you tell me about the signal sent to the ground of the coil please mate.


Is it


ground for ages, then pulse to break the ground, or is it nothing then quick bit of ground following by back to nothing?


As I think I may have misunderstood how this works, I was thinkig it was mainly in a ground state, but is that actually wrong and its mainly in an open circuit state and only flashes momentarily to ground?

ECU Monitor Enthusiast

iTrader: (1)

Modern ignition systems have dynamic coil charge (dwell) times.
This results in a uniform spark delivery at all loads.

The ignition amp on a cossies for example when told to charge the coil,
will drive the coil negative to zero volts putting the full 12 volts across it.

This results in a current of about 10 amps to flow.
This situation is called saturation.
If this condition stayed, the coil and amp would burn out in seconds.

After about 3 milliseconds, the amp backs off the drive, raising the coil
negative voltage nearer 12 volts until it measures about 5 amps
going to the coil and then holds this level.
This will NOT produce a spark even though the coil voltage across it
could have halved or more.
This is because any emf produced is absorbed by the current flowing in
the primary winding which reduces the secondary output to a point where
it is unable to spark.

A sudden release of the coil negative to an effective open circuit produces
a strong spark from any of these points in the charge cycle due to the
magnetic field being saturated given it has had time to build up.

If you reduce the drive voltage slowly to the point of open circuit then
no spark would be produced but this depends greatly on time
and coil design.

The off state is open circuit.

So the cycle is...

OFF
CHARGE FULL POWER FOR 3 milliseconds ish
REDUCE POWER to 5 amps
SUDDEN SWITCH OFF generates spark

Chip

iTrader: (3)

Arse, although its slightly more complicted than I thought, it is actually effectively the same as I thought then in terms of how it would respond to a cut (ie pulling either +ve or -ve will cause an event)

GARETH T

remember simons just talking about modern spark systems... on an old dizzy, it was just dwelled by the points being closed, and when the points opened, a spark was produced

Chip

iTrader: (3)

Yes mate, ive no interest in points based systems, even my a series mini is converted to electronic anyway.