Magnetos (not particularly Minor related)

Post by **Cam** » Sat Oct 22, 2005 4:14 pm

Not sure 100% but I would imagine that the spark produced by the coil system is bigger than that of the magneto, so when engine technology was improving and compression raising maybe the magneto was insufficient. Also with the cars moving over more and more to battery powered equipment I guess it makes sense to move the ignition system over too. Besides which, the coil system is far more flexible and you can have as much spark as you want and as often as you want too!

Post by **woo** » Sat Oct 22, 2005 6:54 pm

Magnetos are still used in things like Lawn Mowers. They are very reliable and produce about 20,000 volts. Small aircraft engines still use them because of their reliability. I think that basically the coil system is now used because of cost.

Post by **Futurebobbers** » Mon Nov 21, 2005 10:25 am

This sounds familiar. My (carb) Fiesta doesn't have a distributor. I don't fully understand it, but it's got something called a 'coil pack' where the HT leads come direct from the coil. There's a missing tooth on the flywheel and each time that does a complete turn, the coil pack fires out four sparks.

Post by dp » Mon Nov 21, 2005 6:53 pm

Aha good old Ford EDIS. Two coils and wasted spark, popular with Megasquirters so probably very reliable. Much info here:
http://www.dainst.com/info/edis/edis.html

Post by **lowedb** » Mon Nov 21, 2005 7:32 pm

My (carb) Fiesta doesn't have a distributor. I don't fully understand it, but it's got something called a 'coil pack' where the HT leads come direct from the coil.

A variation on quite a common theme. You have a double ended coil providing a spark to two cylinders at once, but one is on the exhaust when the spark comes so is 'wasted'. A four cylinder engine needs two like this.

There's a missing tooth on the flywheel and each time that does a complete turn, the coil pack fires out four sparks.

Well actually there'll be a computer somewhere, even if it's a dead simple one.. It will recognise the missing tooth (in a special ring attached to the fywheel) as TDC or a certain distance from TDC. From this it knows when to fire each coil, so no spark switching device is needed. If you have only two cylinders, you can get away with points as you only have one coil (2CVs).

Post by **Futurebobbers** » Tue Nov 22, 2005 11:30 pm

Yes, that's it, the wasted spark system. There is a little computer of sorts on the bulkhead, but it's referred to as an ignition control module rather than engine control.

Any reliablity problems with the system seem to come from water getting into this module - Ford did a recall to fit some part but my car apparently missed this. But it's been reliable enough for me, and thankfully maintainace free for the lazy motorist.