Are you smoking crack?! 8.5:1... No way dude, you dont want to go under 9.0:1 on any motor or you start having a problem with volumetric efficiancy.... Unless of course you are boosting INSANE amounts and need the space to avoid detonation. (Insane = 25+ PSI with loads of flow)
A Hi-Compression piston does alot of things (Besides making an engine "Work arder") Higher compression pistons work by squishing the fuel harder, they usualy involve a higher dome to take up a little more space in your combustion chamber. The only reason you would need higher octane fuel is because it is not as volatile as lesser octane grades and therfore will not detonate untill a higher flash point is reached. Basicaly, it takes alot more squish to explode 91 oct than it does to explode 89 oct.
Another thing that piston makers do is try and tune the piston to sound wave lengths in an attemp to better Homoginize your air fuel mixture. Plenty of other things are taken into account such as flash points and detonation grooves.
On a normal honda piston, if you detonate... thats pretty much it, I wish I had my old piston to show you. Anyway, the forged pistons are MUCH stronger and lighter.
If you have any further questions, go read a book... Thats were I learned all this shit.
