Re: octane levels per compression point?

[Brad Sheridan <brads@mindspring.com>]

At 09:32 AM 9/9/99 -0400, you wrote:
>
>    does anyone know if there is a formula or table that can show me what
>octane is best suited for my engine?
>
>    for instance, if i'm driving a car with 14:1 compression, i'd obviously
>get more out of the motor with 94-grade over 89-grade fuel.  but what is the
>limit?  would i be able to put in 100-octance fuel and see an increase?
>when does it start becoming a waste of time?  thanks

  AFAIK, there is no set relationship here, unless you are talking about
for one particular engine. Combustion chamber shape, spark timing, engine
temps, etc, all play a role in this. My bike runs much better on 89 octane
and has 11.2:1 compression. My 16V seems to like the 92, or higher if I can
get it, the compression on it is stock, which I don't think is quite as
high as 11.2:1.

  I used to run pretty advanced ignition timing on my 8V, and 100+ octane.
It seemed very quick on the top end, but I never dynoed it. So it could've
been just that the bottom end lost so much, the top end just felt really
strong by comparison.

  If you want to take advantage of higher octane gas in your engine, try
advancing the ignition timing some. 


Brad


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