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Bob uk
Unregistered guest
Posted From: 94.197.122.85
Posted on Thursday, 31 July, 2014 - 07:54:   Edit PostDelete PostView Post/Check IP

Or capacitors.
I thought I knew how a capacitor worked within a ignition circuit bit since studying resistor capacitor time constant circuits I now know that the capacitor does a lot more than just stop the points burning and give a clean break
I was reading about res/cap tuned circuits and time constant times 5 known t5.

In a picture of a oscilloscope trace is 5 squiggles showing t5 which was exactly the same as a spark trace for a car.
The inductance of the coil and the capacitor act as a tuned circuit.
This prolongs the spark
The first bit of spark is high energy which starts the arc and breaks the "ice at the party" then the back emf makes another spark 4 times as the tuning vibrates then it runs out of steam.

The explanations on this site of capacitors was I thought more or less correct. Not quite.

This info is of no use for repairing cars but nice to know why and how.

(Message approved by david_gore)
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David Gore
Moderator
Username: david_gore

Post Number: 1416
Registered: 4-2003
Posted on Thursday, 31 July, 2014 - 13:02:   Edit PostDelete PostView Post/Check IP

Thanks Bob,

You learn something new each day - making the coil and points HT system a tuned circuit is a very clever way of achieving a useful benefit at minimal cost.

I wonder if the later electronic systems use the same technique?
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Bob uk
Unregistered guest
Posted From: 94.197.122.73
Posted on Friday, 01 August, 2014 - 05:54:   Edit PostDelete PostView Post/Check IP

Yes capacitor discharge ignition ramps up the idea.

Since yesterday I also now think that by using coils and capacitors that are precisely matched to the maths would result in stronger spark not sure though.

(Message approved by david_gore)
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Bob uk
Unregistered guest
Posted From: 94.197.122.87
Posted on Monday, 04 August, 2014 - 06:57:   Edit PostDelete PostView Post/Check IP

Tuned rc circuits focus to one place and the harmonics. Because an engine is not constant speed. Careful selection of coil and capacitor will not improve the car.
Which ruins my master plan for world domination of the ignition market.

(Message approved by david_gore)