Thread: Ignition 101
View Single Post
  #13   IP: 172.8.29.110
Old 12-06-2013, 11:31 AM
thatch thatch is online now
Afourian MVP
 
Join Date: Dec 2009
Location: Santa clarita, Ca.
Posts: 1,079
Thanks: 235
Thanked 257 Times in 138 Posts
Thank's Joe for posting "Wiki's" version of detonation, however, in the last paragraph they neglected to mention one of the most commonly recommended "fixes" which is to "retard" the timing. In fact most modern day autos have "knock sensors" which sense detonation and retard the timing automatically. In "cutting to the chase" on how detonation or very aggressive timing may be affecting our A4's, I feel that we have to look at the crankshaft and main and rod bearings. As we know the A4 has only two main bearings which means that there is no support next to the #2 and #3 rods. "If", under extreme loads, the crankshaft is flexing (as I suspect) this will definately lead to some bearing wear issues. Recently, during his engine rebuild, Hanley remarked about excessive rod side clearance which may be the result of this "crank flex". A couple of years ago, I recall some photos of some A4 main bearings that showed some excessive wear on the inner half of the crankshaft main cap which I feel also points in the direction of "crank flex".
Tom
Reply With Quote