re: timing and octane

[C1J1Miller@aol.com]

Question(s) for the list:  My '91 200q (3B Motronic dual knock sensors) lists
octane requirements as 87, with 91 for maximum performance.  Later S4 and
S6's list 91 octane required (manufacturer's brochure).  How does the knock
sensor ignition (motronic) work?  is there a range of timing advance that is
possible (max advance/retard); does gasoline with higher than 91 octane allow
additional advance (such as when hot and the ignition would otherwise be
retarding spark); or is higher octane fuel a waste of money?  Also, certain
knock-sensor VW engines do well with setting the ignition advanced, although
they do run hotter (more hp=more heat); does this apply to the turbo motronic
Audis?  Seems to me that is what happens when you use a stiffer wastegate
spring that tricks the computer into allowing additional boost and timing
advance.

Does the ignition maximize advance? (i.e., keep advancing engine timing until
it knocks, then back off), and if so, how often does it cycle through
attempting to advance the spark?  

Does anyone with the Bosche fuel injection book know if it goes into any
detail on the above as it relates to the motronic version used in my car?  If
so, I'll see about getting the book.
Thanks 
chris miller, Windham, New Hampshire, c1j1miller@aol.com