Ignition only

[Axel Rietschin]

----- Original Message -----
From: "Bruce Plecan" <nacelp at bright.net>


> Ooops, meant to delete this off list

A wasted spark DIS uses special "dual" coils which have HT leads connected
to both ends of the secondary (high voltage) winding, unlike a conventional
coil were one side is grounded. Both HT leads are connected to a different
plug (cyl 1 and 4 on a 4 cyl engine, another dual coil taking care of cyl 3
and 2, assuming 1-3-4-2 firing order). When one coil fires, both cylinders
connected to it fires at the same time. On one of the cylinders, the spark
jumps from the central electrode of the plug to the ground electrode, the
current then travels though the head and another spark jumps in the other
direction through the second plug (from the ground electrode to the central
electrode, effectively crossing a second gap) then returns to the coil
through the second HT lead, closing the loop. Technically, the engine
doesn't need to be grounded for this to work, unlike conventional ignition
systems where the current returns through the engine and chassis. One of the
cylinders is at the end of the compression stroke and the other, where the
second - wasted - spark occurs, is at the end of the exhaust stroke where
pressure is near atmospheric, thus that other spark consumes very little
current.

In other words, a wasted spark DIS doesn't save you a gap compared to a
distributor based system. It just moves it.

Need more complete descriptions? Please check

http://www.asashop.org/autoinc/feb97/DIS.htm

http://www.ag.auburn.edu/users/gparmer/efi/myfaq.htm

Regards,
Axel




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