knock sensor

[Hoffman Anthony J A1C 552 CMS/MXMVC]

The knock sensor only opperates when it senses preignition (knocking). They
are a piezoelectric crystal that responds to a certain frequency (created by
preignition), and send a signal to the computer, which then retards the
timing (I believe it is 6 degrees). It operates at all engine operating
speeds. It does not create a fault code, since the ignition system is
designed to work in conjunction with it. The only way better fuel will make
a difference on a stock 100 engine is if you bump the timing over 12
degrees(initial), and this varies from engine to engine. Some go as high as
18 degrees with no ill effects. 

Tony Hoffman


-----Original Message-----
From: Nick Lawrence [mailto:nick at beol.net]
Sent: Wednesday, February 18, 2004 3:43 PM
To: audifans
Subject: knock sensor


I am trying to understand the workings of knock sensors that are on Audi 100
and 200's.
If knock occurs will it make a fault code? 
Has anyone made a way to get instant readings if knock occurs?
Is changed timing the only action when knock occurs? (just what the ecu can
do, not melt down)
Does the knock sensor operate only in a certain rpm band?

In the case of the 100, if there is no noticeable difference in performance
or mileage between using regular (87 octane) and super (92 octane) can it be
assumed that no knock and therefore no timing adjustment occurred?
No I don't risk running the turbo on anything but super! but it would be
good to know if there was ever knock present.
TIA for any insight.
Nick


_______________________________________________
quattro mailing list
quattro at audifans.com
http://www.audifans.com/mailman/listinfo/quattro