I would like to gain an understanding of the spark knock system used in the LT1 and other engines of the time. A while back I purchased a few GM ECMs just to have a look at common parts and do testing that might destroy things. One point of interest is the spark knock filter. Here is a picture of the filter with the elastomeric goo removed.

IMG_1757.jpg

The module contains a bunch of laser trimmed resistors, capacitors and two chips. The first chip is easy to identify, it is a Philips Semiconductor NE532D. This is a very common dual op-amp. The second part is not so easy. It is a "flip chip" design with no package. The part is mounted directly to the board using solder bumps. This can only be done where the board expansion is similar to the semi-conductor expansion. This is the reason it is mounted on a ceramic hybrid.

I started looking at this after reading the thread at: http://www.gearhead-efi.com/Fuel-Inj...-knock-sensors
This encouraged me to look at the system a bit and ask for some help.

--> If anyone knows anything about the flip chip part OR earlier systems that use a similar part in the detection of knock please post what you know. I can only guess that this part is involved in the filtering of signal from the sensor
--> If anyone with an LT1 could give me an accurate measure of voltage on the blue connector pin 13 engine not running/key on. I know there are different modules used (at least two) so if possible post the number of your filter module

The second ask is because I think this voltage is used to level slice the filtered knock signal. The voltage is created using a divider composed of two laser trimmed resistors. These resistors are the ones between pins 2-3 and between 3-4. I have yet to set things up and start measuring signals. To be honest, the whole system is a bit confusing. In any case this is where I am starting out.

-Tom