cheap knock detection system..

chris2712au · Post by **chris2712au** » Sun Jul 26, 2009 1:33 pm

take a look at this.. I like this site for diy projects..

http://www.autospeed.com/cms/A_0353/art ... larArticle

Alrick · Post by **Alrick** » Sun Jul 26, 2009 2:22 pm

nice find!

brother_david · Post by **brother_david** » Sun Jul 26, 2009 6:10 pm

We have been using a ordinary Stethoscope and a longer hose on the last couple of builds, works a treat if you know your engine

We do check for knock with knocksensors just to be sure but havent had a reason to alter a tune yet!

Stethoscope "Sense your knocks the analog way"

Matt · Post by **Matt** » Mon Jul 27, 2009 1:08 pm

we found the other day that the factory knock sensor in the RB30ET ECU was not picking up knock that PL was hearing in his headphones. So headphones/stephoscope are still the go from what I can see so far...

Delox · Post by **Delox** » Wed Sep 02, 2009 4:41 am

Made a knock sensor using this method, however I am not too sure of how reliable it is. I sealed off the clips as best as I could with a glue gun, but I am still not sure if I am hearing the engine well. I clipped one clip on to each head/block mating surface at the rear most cylinders (v6), so that is optimal.

Would it be safe for me to advance the timing a lot at a low rpm (say 3k) and low load (say free reving) to induce some detonation just to make sure I know what to listen for? I would only do this for a moment and I believe since there is no load there would not really be any damage inflicted on the engine. What do you guys think?

chris2712au · Post by **chris2712au** » Wed Sep 02, 2009 8:48 am

you have to really get down under the inlet manifold.. whete the stock one should be approximately where the crown of the piston is at TDC.

Also make sure the micropnone has no gap between it and the clip...

Delox · Post by **Delox** » Thu Sep 03, 2009 4:24 am

Unfortunately its not possible to get the location of the stock sensor on the 300zx vg30dett engine when its installed in the car. Here is a picture of the locations I chose. The stock location is down that black hole you see between the cylinder banks. Once the engine is installed the transmission and downpipes make it impossible to contort your hands to get up in there.

I think I will remove the clips and try to better install the microphones, also I think I may secure and insulate them with something more solid (I'm thinking JBweld)

I'm worried it may be a waste of time and I ought to be looking for a more professional unit to detect knock with, however I'm not sure I can justify $300...

chris2712au · Post by **chris2712au** » Thu Sep 03, 2009 4:54 pm

oh I see your problem... the SR is pretty easy to work with in terms of getting to the knock sensor...

For your engine I would try actually listening to the knock sensor itself.. meaning

http://forums.focaljet.com/ecu-tuning/6 ... ensor.html
http://home.netcom.com/~bsundahl/knock/ ... listen.htm
http://home.netcom.com/~bsundahl/knock/ ... Sounds.htm

hope that helps.. Never tried it myself.. but make sure you decouple the connection with the capacitor..

Delox · Post by **Delox** » Sun Sep 06, 2009 3:39 am

Interesting. I'm not sure if it's possible for me to get a hand on the sensor while it's installed however. I'll have to try breaking some bones and seeing if I can get at it.

Thanks for the links, I'll look into it.

chris2712au · Post by **chris2712au** » Mon Sep 07, 2009 5:46 pm

they are saying you can tap into it... while it is connected to the ECU..

Delox · Post by **Delox** » Wed Sep 09, 2009 12:48 pm

Well that would be true but unfortunately my knock sensor has a wiring issue with the clip right on the sensor itself.... Now you just made me think because the issue was intermittent and would throw bogus knock codes, so maybe I will be able to listen to be before without that issue completely disabling its function.

PL · Post by PL » Wed Sep 09, 2009 3:55 pm

Think I've said this before, but it's a lot easier to actually hear knock if you use a microphone that's insulated from the engine, rather than connected to it. This allows you to hear the important knock sound without all the mechanical clattering going on inside the engine.

PL

chris2712au · Post by **chris2712au** » Wed Sep 09, 2009 4:53 pm

thats right I remember the mic in a can... was effective too might have to see if I can find the pics.. I think you had posted some as well

PL · Post by PL » Wed Sep 09, 2009 4:58 pm

Yep. I actually wrap the whole mic carrier in sound insulating material and then often I'll even wrap a rag around that. Leaving just a small hole going to the mic. This is then stuffed under the inlet manifold facing the block.

PL

TM_S13 · Post by **TM_S13** » Wed Sep 09, 2009 7:12 pm

hum... interesting...

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cheap knock detection system..

cheap knock detection system..

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