I run 87 octane all the time and tried 110 race just once, The only thing it did different was make the exhaust smell better. No real improvement until real mods are done.

 

Alot of the newer engines such as the Cannondale & YZF are running 12.5:1 on premium pump. Im running (When its running, anyhow)
Premium in my DS and it has a 11.5:1 Piston in it

 

I run 91 - 93 octane and never have a problem.

 

my z is 12.2 to 1 and i run fine on premium no sighns of detination and i have ran race gas in both my yz 426 and the z and i think they ran worse the yz runs best 50/50 race and pump

 

Water cooling is another reason Suzuki can run higher compression. It helps to keep the engine at a cosistent temp.

 

Lemme jump in here too.

Octain rating and compression ratios are usually determined in V8 car engines,cast iron heads,wedge chambers, bores of 4 inches or more and relativly low rpm's.

The larger the bore the more problems you will have with detonation.The Z has a relativley small bore.

The combustion chamber shape playes a factor also.A wedge shaped chamber will detonate before a hemi will.

Aluminun conducts heat much better than cast iron.Z has an aluminum head(as do most bikes)

And as stated earlier valve overlap lowers the dynamic compression ratio at low rpm's.

At max rpm theres prolly not enough time between firing cycles for detonation to occure,thats why you may only hear it when it's "bogging".

Air cooled bikes need higher octain because they tend to run very hot.The "normal" cylinder head temp for an air cooled bike is much hotter than a water cooled bike will ever see,even if it's is overheated and boiling out the water.

hth