Re: Super unleaded, again, long and hardly worth it.

[audistuff@juno.com (Paul R Anderson)]

O
>What I am unsure about is how a highly knock resistant fuel would give 
>better 
>engine performance than one of lower knock resistance, assuming that 
>pre-ignition (pinking?) is not present with either fuel? Does it mean 
>that you 
>can have more advanced ignition timing with a low knock resistent 
>fuel? If so,
Graham,

On an engine with a knock sensor ignition, it will retard ignition timing
to 
compensate for low octane and to prevent pre-ignition.  This affects
performance.
There is a limit to how much the ignition can compensate and so if you
use
poor enough fuel, it will still ping.  Going with higher octane than it
can 
use is a waste because there is a limit to how much timing will be
advanced.


Probably the best bet is to use recommended octane.  Any higher will be a
waste and any lower will hurt performance and, in the extreme case, cause
pinging.


Paul Anderson, Cheyenne, WY  Private email:AndersonPaul@juno.com