I have been looking at the knock module from various LT1 and V6 applications in the late '90s. The circuit is housed in a plastic carrier with eight contacts. Inside there is a hybrid circuit (I believe it is thin film). On the circuit are a number of capacitors (one looks to be a larger polarized tantalum cap), LASER trimmed resistors and two ICs. One of the integrated circuits is a soic 8 pin manufactured by philips (marked NE532D dual op-amp [edit]) the other has a higher pin count (perhaps 16 pin) and is not packaged. The second chip has no markings because it is not packaged. I believe the part is made with solder bumps and is mounted directly on the substrate.
I find it interesting that when manufactured, the hybrid is mounted in the top of the plastic housing with some very low density elastomer. This material is very soft and I believe is used as a sound deadener to prevent flexing of the substrate from becoming microphonic. That is to say that the module could under some circumstance pick up vibrations and turn them into unwanted signal.
I plan to look at this module in the future & try to find it's operation, but for now this is all I have found.
One question for the group... knock is when the compression cycle heats the mixture to the point where it ignites before the spark (pre-ignition). How does retarding the spark seek to cure this? I can see how making the mixture richer might cool things. Overall retarding the timing would cool things when knock isn't present. Perhaps someone could explain?
-Tom
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