Originally Posted by reddy
Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading.
Well if you are not getting pinging then the ECU will advance the timing to it's MAX allowed with the programmed fuel maps. i.e. the car is programmed to run @ say 93 if it get pinging it will retard the timing (loss in HP) till it stops or reaches the low end of the fuel map. Unless you are running more boost you will have no need for the extra octane, being it is running as designed. If anything you will run up your EGT's since a lot of unburned fuel is running through there, and that will also cause a loss in HP.
The best way to get the most out of your car is to tune it for the boost you will be running every day then maybe a seperate "High-boost/High-octane" setup. You can do this with something like the PSI software.
Another thing you can do (what my buddy did) did is tune his car for "street mode" low boost then after it hits a certain PSI his boost controller turns on an Alky System like this one
cooling everything down and bringing the octane level up to 120.
All that being said it will not hurt you too much running a few extra octane. I wish I could find the artical where it actually showed HP going down after a certain level is reached. But anyway you get the idea.
Oh the Stage 2 kit comes with a high octane fuel map too....