why can you supercharge VR's without lowering compression?? (e.g. vortex kits)

Hi there,

just wondering why you can supercharge a vr6 engine without lowering the compression, using a kit??

i realise that the kits use very low boost, but surely by pressurising the air in an engine that is already at 10:1 or 11:1 compression, you would get knock? obviously you dont.. otherwise nobody would buy the kits - just wondering why they dont knock?

also, what is the limit for adding F/I to a standard NA engine? someone said 0.6 bar in another post, if this is true, why arent NA engines running 14:1 compression!
is this limited by the strength of the internals or by knocking?

just out of interest, would it be possible to charge a standard abf and get away with just a remap? can the standard air flow meter handle boost?

cheers

scott