flounder

Guess who's back, back again?

Been looking more into the knock sensor settings on my pnp2 and noticed that I have mine set to disabled. Supposedly pnp2 has the stock knock sensor on my NB already wired up to work from the get go?
Is this true? Does it actually work? I hear an audible knock sound right around 4500rpm that im trying to tune out, but I haven't actually tried turning this "knock sensor settings" thing on yet, is it worth it to try?

rwyatt365

After months of researching, being told that it's not possible, doing more research, fiddling with trim pots inside my PNP2 and lots of head scratching I finally got my PNP2 to read "something". Now, whether or not it is actually doing anything useful is a totally different question.

The key is tweaking the "slope" and "gain" pots inside so that you can get a (supposed) trigger from the output of the knock sensor. Once you get that "working", then it's a matter of selecting the proper settings in the Knock Sensor Settings menu.

flounder

first off, Wyatt, thank you for helping. I think you've been replying to most of my ms threads and i really appreciate it.

So, currently I have it set to safe mode and my knock input pin is "ms2/ad7 js4" My first issue is the knock input threshold screen stays dark and wont let me change anything either on the map, or the rpm chart to the right of it. is there something im missing to light up the grid? all the dots are there, but i cant move any of them around like i could with TPS enrichment.

if its supposed to be controlled out of the box, why do you have to remove and open it? The location of the ecu on the NB is in a really shitty location to mess with it lol

rwyatt365

No sweat. I'm here to help when I can - and learn when I must.

The only way to be able to get to those dots is if you set "Input Type" to "Analogue". I don't use it because the NB knock sensor is an on/off type (you don't get a continuous output that's relative to the amount of sensed knock - or so I've been told). I don't use that. What you have to do is to "tune" the response of the MS to the output from the sensor such that a "real" knock event will peak above a noise floor. All of that is controlled by two trim pots inside the MSPNP2; one adjusts the "noise floor" (the "Slope" pot) and the other adjusts the strength of the signal from the sensor (the "Gain" pot). Getting that right is like setting toe and camber in the suspension - adjusting one affects the other, and often adversely.

You have to put the MS into "test mode" (via some jumpers), and then tweak those pots until you get it right. It took me weeks of trying to figure out what does what and then turning trim pots until I was about to give up, until I was able to get something that resembled what I thought was right. Even now, I'm not so sure that I'm actually reading knock, but at least I'm getting something that kinda makes sense. I'm not using this to do major ignition retardation in a "knock event" - I'm using it as a tuning aid to fine tune my ignition timing to avoid those (pseudo) knock events.

My main reference was in the MSPNP2 install manual (MegaSquirtPNP by DIYAutoTune.com). About halfway through is a section on the jumpers - this is where you find how to set the MS into "test mode". And then almost at the bottom is a section about Knock Sensing - that's where you see about tweaking those trim pots (while in test mode). For me, the hardest part was getting to the point of having a useable output from the sensor by tweaking those pots. THAT was excruciating!