8 cycling 4 stroke?

[Ross Burbidge]

bruce plecan wrote:
> 
> In the new Sport Compact Car (Apr 98) they memtion, big
> cammed V-8 engines, only firing every other compression
> stroke, at idle !!.
>   Can any one comfirm this?.
>   I've had some big cammed motors, on various scopes
> but I've never seen a cylinder fire every other time.  May
> be I missed something here.  I've seen short burn times,
> and erratic firing voltages, but firing every other compression
> stroke, that doesn't seem likely.
>   Bruce
Hi Bruce,
What they probably mean is combustion is only taking place eveery other
stroke. The plug fires every comp stroke but due to the high overlap
of the wild cam(intake & exhaust valves both partly open ) the next
incoming
mixture is diluted by exhaust gases from the previous combustion which
haven't 
all vacated the combustion chamber yet and burns poorly(or not at all?).
The 
following intake stroke restores the correct mixture balance so the next
comp stroke fires OK. Then the '8 cycling' starts again! Hence the lumpy
idle of a big-cammed engine. I guess lean-burn engines are examples of
how
to make use of lean & partly burnt mixtures. The gains are in emmissions
and
economy but not really power, I think. Does anyone know the mechanics of
how 
the Mitsubishi GDI(gasoline direct injection)series engines combine
incredible 
economy and power? 
Ross