12 replies to this topic

[miniboo]

What does the condenser do?

i think i know what it looks like (small cylinder mounted on the bracket with the coil) but mine is not connected!

Does it matter?

I have electronic ignition if it makes a difference.

[Guess-Works.com]

The condenser prevents arcing across the points, and as you say, pointless ( ) in an electronic ignition...


Pointless..... I kill myself sometimes :cheese:

[miniOwnerGetMeOutaHere]

true - but the device described by miniboo is more normally referred to as a suppressor an not a condenser (although it is still a condensor, just a different value)

Its function is to reduce the rfi caused by ignition sytems and is most noticeable as interference on tv signals

[Guess-Works.com]

True.... :fear:

[dklawson]

Pointless, pointless, pointless...

You kill me too!!!!

[miniboo]

lol at guessworks.

so do i need it or not?

guessworks says no but miniownergetmeoutahere says yes...i think.

[minimole]

if you let guesswork kill you then you eont need it :fear:

[minimanclive]

Leave the suppressor on the coil. If only to stop my freeview picture breaking up when things with un suppressed ignition drive past my house ) LOL

[Guess-Works.com]

As miniOwnerGetMeOutaHere has said what you have called the condenser is actually a suppressor for noise ( that lovely clicking you hear through your radio when it is on AM or LW ) and has nothing to do with the actual ignition system of the car.

The Condenser I described is a unit which is part of the points ignition system which is not required if you have an electronic ignition

[Dan]

Not true, not true, not true.

The can mounted on the coil bracket is not the condenser. As said above it is the suppressor. Both the condenser and the suppressor are capacitors, but they do very different things. The suppressor is indeed only there to stop RFI "leaking" out of the ignition system.

The condenser is a capacitor mounted inside the distributor on conventional contact breaker ignition systems. You need to know how the system works to understand what the condensor does. The HT side of the ignition system runs at several thousand volts, which to be supplied by a 12v system needs a transformer. This is the coil which is a very basic conventional solid core wire wound transformer. Before cars had other electrical items needing 12v a high voltage generator called a magneto was used, but that's a whole different story.

As you may know a transformer can only generate a voltage on the secondary side when the primary side is running alternating current because they are basically a generator and a generator works by moving a magnet in relation to a coil of wire. In this case the coil of wire is the secondary coil in the transformer, the magnet is the electro magnet formed by current existing in the primary coil and the movement is simulated by the current being applied and released which is why you need an AC supply not DC.

Sadly a cars electrical system runs DC as it runs off a battery and traditionally a dynamo which supply DC. Since the introduction of alternators it would have been possible to switch to AC but there are many advantages of DC.

So in order to produce an intermittant current in the coil primary we use a contact breaker in the distributor which applies and releases the current as the engine turns. The other advantage of this is that it is possible to precisely time when the current in the coil is changing enough to produce an HT output in relation to the position of the engine. It would be possible to use just the contact breaker and get some form of spark but it would be rather weak.

This is because if you just used a contact breaker there would be some sparking at the points as they open. This would have two effects, it would firstly increase the time it takes for the current in the primary to reduce to zero as the spark would be conducting current and there fore the circuit would not simply turn off when the points open. This would mean the secondary was not generating as high an output as it would otherwise. Think of the time it takes to drop the current to zero as being the same as the speed the magnet is turning inside a generator, the shorter the time the faster the magnet. So if you can get the time as close to zero as possible (zero time is impossible) you can generate a much higher output at the secondary. Secondly it would lead to the points breaking down in very short order as the spark at the points would erode them.

By fitting a very fast charging capacitor in parallel to the points you can effectively eliminate the risk of a spark when they open as the capacitor will actually force the current in the coil to stop flowing very quickly indeed once the points are opened, and it will 'buffer' the voltage away from the points as they do. When the points then close the capacitor will discharge ready to be used again.

So it makes your points last longer and the spark fatter.

Sorry if that was a bit technical.

[Wiggy]

No no, you explain away. I've just learnt something.

[miniboo]

ok now i see what you mean.

so it doesn't matter which connector on the coil i connect the spade end of the suppressot to?

[Dan]

Yes it does, very much so.

If you put it on the -ative side (the side connected to the dizzy) then you will effectively be adding another capacitor in parallel with the points. This will badly effect the ignition system performance and it will do nothing to isolate the interference.

What you are aiming to do with this capacitor is to eliminate the current which is reflected back through the coil as the points open and close and the secondary circuit charges and discharges. This is something which happens to all coils of wire (even the windings in relays and motors) as a byproduct of what they do and it is this which causes the coil to transmit interference. It's called self induction. So what you want to do is make sure the same thing the capacitor in the dizzy is doing at one end of the coil is happening at the other end by adding the suppressor to the coil supply, the positive terminal.

Edited by Dan, 23 November 2005 - 12:32 PM.