How to test knock sensor circuit?

[billjam]

Is there a simple way to check that the knock sensor module and sensors are working?
I have run logs and the knock readings for all cylinders are 0%. I don't know if this indicates that there is no signal at all or there is no knock.
To confirm that everything is working, is there a knock setting that can be adjusted to create a signal, even if it is just to pick up noise?
I have the MS internal knock sensor module and two OE Bosch sensors wired through pins 4 and 6 as below.

Sensors wiring a.jpg

[Dennis930]

Bill,

Something is wrong, you should be seeing a varying signal for each cylinder in the datalog unless both sensors are bad, which I doubt. I did have to change my sensor when I had the engine out for a clutch job because the sensor I had previously installed for an earlier "Knocksense" knock sensor was bad, which I found when I wired up the MS3 knock board. Is your MS3 mainboard V3.57? and was the knock board installed when you purchased it, or did you install it? This could be an issue with the MS3 knock board installation or a wiring issue. If you have continuity for the wiring to pins K1 & K2 on the knock board, then either the sensors are bad, the knock board is not installed correctly, the knock board is bad or there is a set up problem in TS. Did you assign the cylinders for each of the sensors and are you seeing the gains for each cylinder (default is 1.0) I do not believe there is a way to test this out without running the engine. That is because of the knock windowing.

[billjam]

Dennis, I worked through your setup notes in my PP thread but drew a blank, well 0%! The cylinders are assigned.
I guess there must be a wiring issue. I installed the knock sensor module on the V3.57 board a couple of years ago, but haven't tried to activate it until now, so I'll need to go back to square one and work through that installation and check the wiring. It seemed pretty straightforward at the time, but maybe I got something wrong.

[Dennis930]

Bill,

You should be seeing something like the screen shot below.

[billjam]

Thanks, it is handy to know what I'm looking for. I figured this wasn't right!

knock log.jpg

[billjam]

I took my MS box apart today to recheck the wiring and found that some of the six connecting pins on the knock module had bad connections, probably damaged during handling during the 100+ times I have had this box apart.
Anyhow, wiring checked out OK and after resoldering the mounting pins, I now have signals from both sensors. Now I just need to figure out what to do with them!

Dennis, I was planning to hook up my speedo sensor to log speed and I see you have it in your log above. Do you have details of the connections at the MS3?

knock log.jpg

[billjam]

Looking at the log above, it seems that only cylinder #1 needs gain adjustment to bring it into line with #2 and #3 (which are LHS sensor on a Porsche engine).
On the RHS, cyls 4, 5 and 6 seem to have fairly similar readings.
Bored tonight, so plotting the data into Excel with a bit of smoothing makes it easier to see what's happening. Interesting that each side of the engine has different sensor outputs in relation to RPM ... LHS is reasonably independent of RPM, yet RHS is directly related to RPM.

Knock sensor outputs.jpg

[Dennis930]

Bill,

For VSS hook up, you need to tap off from the pulsed signal from the hall pick up sensor mounted on the transmission. There is a connector for it in the transmission tunnel. Find the green wire, or what ever wire that is connected that does not read to ground at the speedometer. The other wire from the sensor goes to ground at the speedometer. The MS3X input is looking for a ground input, so when a magnet in the transmission passes the sensor, it makes, and provides a ground pulse. There are 8 pulses per wheel revolution. You have a choice of "D/log In" (pin 30), "Launch In" (pin 11) or "Table Sw" (pin 28) for your input to MS3X. Fill in all the wheel and transmission data in TS. TS will also tell you what gear you are in when all this is working. Be prepared for seeing your speedometer not agreeing with TS because Porsche speedometers usually read fast.

As for the knock signals, The RHS looks good. The LHS may need some tweaking of the gains. I have a single Bosch knock sensor mounted against the block under the throttle console. For some reason cylinder #4 reads higher than all the others and it is nearly the farthest from the sensor. I had to turn the gain way down on that one. I am not sure how to interpret the readings. The only clue is the 50% line in TS knock setting. James has suggested lugging the engine at low RPM's to see what a knock signal looks like for your particular engine. I have not tried that because 911 engines don't like it. Being that we are twin plugged, that reduces the chance for knock greatly. I saw a 60% reading in a datalog yesterday, but I have not checked to see if it triggered a knock retard event (I am still trying to get electronic boost control under control).