Technical wasted spark engine?!

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Technical wasted spark engine?!

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Jan 17, 2015
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Hi,

I was doing a little research this morning when I came across information relating to the 1.1 and 1.2 FIRE engines being a wasted spark engine.

It did relate this to the FIAT 500 engine, which I thought was bizarre as I only thought this would have related to the 90's MK1 Punto, maybe early 2003-4 Pandas.

Anyway, apparently the FIRE engine 1.2 and 1.1 have always been a wasted spark unit. Whether they be SPI or MPI engines.

Matt.
 
It's very common these days to waste a spark on a four stroke engine.
It's easier to tigger without a distrubutor for a start.

To fire a four stroke engine, the igntion should fire once every two revolutions of the crank (4 strokes of the piston, hence the name).
So this is needed:
Suck Squeeze*Bang Blow Suck Squeeze*Bang Blow and so on.

It's far easier for the ignition to pick up a signal from the crank/flywheel once every revolution rather than once every two, so it triggers the ignition once every revolution.

As the four stroke takes two revs to complete it's cycle.
One spark makes the bang when needed.
Suck Squeeze*
The other is wasted as it's not needed.
Bang Blow*.

So it goes Suck Squeeze*Bang Blow*Suck Squeeze*Bang Blow* and so on.

So it wastes a spark on a stroke that doesn't need it.
(* is the spark)

There are no real costs to running like this, perhaps a small slice of plug life.
The alternative was/is a distributor, these were driven from the crank at half speed so took some engine power to drive.
 
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A conventional HT coil has one end of the high tension winding earthed. If, instead, both ends have HT leads, you have a double ended coil. My Honda Benley 200cc twin had only one coil as it had a "360 degree crankshaft", both pistons at TDC at the same time. Only one set of points were required. The wasted spark is on the exhaust stroke where it does no harm.
 
A conventional HT coil has one end of the high tension winding earthed. If, instead, both ends have HT leads, you have a double ended coil. My Honda Benley 200cc twin had only one coil as it had a "360 degree crankshaft", both pistons at TDC at the same time. Only one set of points were required. The wasted spark is on the exhaust stroke where it does no harm.
The old 2CV used to work like that too - looked odd to see the coil, which was more or less the first thing you came to under the bonnet, with a plug lead on each end (only 2 cylinders there too, of course)...
 
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