Purpose

As you try to get more and more performance from an engine, you need to take more and more precautions so you don't blow anything up :)  A knock sensor will sense when the engine is knocking or pinging;  two situations which can cause your engine to fail and fast!  If you plan on advancing the ignition timing above 12 degrees BTDC, or if you are having problems with knocking, this upgrade is a must for you.

Find an 8v Volkswagen with a knock sensor (16v will work too, but will have a higher rev limiter).  Get the distributor, the wiring (including sensor part) and control unit (brain).

There should be a place to bolt the sensor to the side of the block, to the front of the car and a little above the oil filter flange.   Bolt it there.  Replace the distributor with the knock sensor one (make sure to block off the vacuum lines to the old distributor, or you'll have problems!!).  Find a nice clean place (out of the way, but not in the elements too much!) for the brain, mount it, plug it all in.  Basically the knock sensor will "hear" when the motor pings or knocks (from poor fuel, high compression, etc...), you won't hear it, but it will.  It will tell the distributor when it has to retard the timing in order to prevnt knocking. Which means you can now advance the ignition timing a few degrees (turning the distributor advances ignition timing).

The total price for all of the above should come to around $150-200 USD or so (used, from a junkyard).

Big thanks to Josh, a fellow VW enthusiast for this information!!

If you have any questions, you can e-mail me, but because I haven't performed the upgrade myself, I cannot relate anything from experience; you can also contact Josh with questions about this.