Tuning O2sensor Knock Sensor Engine Damage

[jon hanson]

I know I'm a day late, but here's my 2c worth on ignition advance / octane etc

>> This sounds suspect. My street car (10.4:1 compression) detonates
>> just a touch at WOT on 93 octane. If what you are saying is true, I
>> would loose torque (and therefore power) if I ran AVGAS.
>> 
>> I don't believe this for a second, what's your source for this
>> information?. Who's R&D?
>
>I think what he means is that peak efficiency for that octane of gas. 
>Higher octane fuel is slower burning, and will take more ignition
>advance.  More advance, more power.  With higher octane fuel, that point
>of detonation usually goes up.  That leaves a little more room for
>ignition advance.  

Egines produce best torque when peak cylinder combustion pressure reaches
a max approx 15 - 20 deg ATDC. I suspect the exact amount varies from
engine design to engine design (what Landshark said about every design
liking a diff comb of AFR / advance etc)

if you cannot advance the timing enough to reach this angle before detonation
sets in the the engine is knock limited with respect to the fuel it is running

Running a higher octane fuel helps in this case. If you read the gasoline FAQ
(by Bruce Hamilton, apologies if I got the name wrong)
the oxidation of a higher octane fuel produces molecular species in the end
gases which are less prone to autoigntion. ie it has more resistance to knock,
it does NOT burn slower than a lower octane fuel.

on the knock limited engine this would allow you to advance the timing to the 
most efficient point. on an engine that was not knock limited, you would
be wasting your money on higher octane, just set timing for max torque at 
minimum advance.