Waste spark ignition

[touringcamry]

I was reading another thread and Ken4 said that Gen4 has waste spark ignition and that each plug fire twice during a 4 stroke cycle.

What is the purpose of this design and how does it fire twice?

I read this:

Originally Posted by ken4

What happens in waste spark ignition is that 1 coil pack fires 2 spark plugs simultaneously, e.g. cylinder 1 and cylinder 4. So while one spark plug is firing normally, spark jumps from center electrode to ground electrode, the other spark plug is firing in reverse, i.e. from ground electrode to center electrode,

But it doesn't sound like it's firing twice, just that each plug fires differently from which electrode to which...

[HoboJoe]

I have never heard of the two firing thingy and don't want my brain to start seizuring while I try to figure it out. Interesting though, hopefully someone else can shed some light on this.

[Gary_602Z]

http://www.autoshop101.com/forms/h41.pdf

Gary

[Tony the Tiger]

^^

Too much reading for a simple answer..lol

Wasted spart fires two cylinders at the same time, but one cylinder is at perfect timing (combustion stroke) and the other is during exhaust stroke ("wasted"). Most likely, the exhaust valves would still be open during the wasted spark so even if there are end gases, it will just backfire slightly.

[zoni]

on gen 4+ 1mz, the coils fire like that... gen 3 1mz, the coils fire all indipendantly.
i learned this while trying to tell a solara guy that he didnt have a MSD DIS4 running, and he actually did. he can, because he essentially has 3 triggers, i have 6.

[touringcamry]

What is the purpose of the waste spark? Is it attempting to burn some unburned gas remaining in the chamber?

If so and the exhaust valves are open, wouldn't that push the combustion into the exhaust manifold like a anti-lag system used on rally cars. The car isn't turbo so there wouldn't be wear on the turbine...but is that what happens?

[zoni]

if you want to know more about this, check that link out that gary put up.