The knock sensor ignitions will adjust the timing to a maximum point and
that's all.  Say for example using 87 octane fuel at 3000 RPM the timing is
+25 degrees - on an engine with +6 static timing the actual timing would be
+31.  If you used 94 octane the timing would still be a total of +31 - if
the static timing was set to +12 the total timing with the 94 octane would
would be +37 where is may only be something like +33 with 87 octane due to
engine knock.

As to how much xylene or toluene you have to add - I have no idea - pretty
toxic stuff!

At 10:17 AM 21/12/1999 -0800, Dana Morphew wrote:
>Do all knock sensors adjust the timing through a range of degrees above
>and below the adjusted distributor setting?  Do you know what the range
>is?  How much xylene or toluene would one add to a gallon of 87 octane
>to change it to 92 octane?  I've been adding fuel conditioner at each
>fillup for my diesel Caddy, so this would not be an inconvenience at
>each fill of my Vanagon.  I'll have to check on the cost of xylene and
>toluene to see if there is money to be saved here.  Thanks for the very
>informative post, David.
>
>-Dana-
>
>David Marshall wrote:
>...
>> all done using a 1982 Rabbit Distributor with vacuum advance and vacuum
>> retard - generally considered the best performance non-knock sensor
>> distributor.  If there was a knock sensing ignition present, there would
>> have been no knock as it would have retarded the timing until it
>> disappeared - thus giving you less power.  With 87 octane fuel in a high
>...
>
>

--   David Marshall -                    - Quesnel, BC, Canada   --
--    78 VW Rabbit, 80 VW Caddy, 84 VW Westie, 85 VW Cabriolet   --
--       87 Audi 5000 Quattro, 88 2.0L VW Syncro Double Cab      --
-- David's Volkswagen Home Page        http://www.volkswagen.org --
-- Fast Forward Autobahn Sport Tuning  http://www.fastforward.ca --
-- david@volkswagen.org (pmail) or vanagon@volkswagen.org (list) --