Ok, here are some pics of my little homemade knock monitor. I have a microphone that clamps onto the block and then transmits so that it can be monitered using the fm radio in the car. I have seen these made where you use a set of headphones, but this is the first I've ever seen of it's type.

Let me know what you guys think.

The little aluminum box has a pot in it to scale down the voltage from 12 v to about 5v. It also contains the preamp circuit for the microphone.


The black box is the transmitter. It is powered by 12v and is intended to be used with dvd players installed in cars so that you don't have to hard wire them in.


Here is the mic. It is hot glued to a clamp that attaches to the block. Vibrations carry through the metal and transmit nicely.


Does it work? Yeah, it works, but I need to get it tweaked just right. I'm going to mess with the voltage in order to adjust the sensitivity of the mic. I am also picking up some interference likely because of a ground loop problem. I am considering just using a 9v battery to power the preamp or wiring in some sort of a coil (like the ones that can be used with head units to reduce interference--)

Now, as soon as I get my ecu chipped (hopefully next week) I can get some dyno time and advance my timing until I begin to hear knock or preignition and back it off a couple degrees from there.

 

Nice DIY project...

I understand its difficult to distinguish between knock and normal engine noise. To improve the S/N ratio the knock sensor is usually located closer to the place the knocking comes from, ie the top of the block. I would advise to get a bolt that fits the original knock sensor hole and glue your microphone to that instead of the intake manifold support bracket (?).

I'd be interested to see (hear:-) the sound clips you'll generate!

Mark.

 

Thats awsome. You also have the right idea as to advancing timing untill knocking then backing it off. Don't be surprised if it knocks pretty bad with a "conservitive" tune. Everybody that really listents to their engine is usually surprised at how much it knocks and how sensitive they are to SMALL tuning changes.

 

Cool idea, keep us updated

 

thats nuts. Keep us updated.

 

That is very cool man. I like your romulator too.

Do you have any plans to filter the signal? If I were you, I would do that. I've been thinking about building something similar, and I know that I am going to use a passive bandpass filter with a high rollover rate to help filter out the extraneous crap.

 

nice DIY

 

Hardcore, def. let us know how it turns out, check it against the plugs to see how well it's performing

 

diy keep us updated cause i want to something like this...

 

I'm into this thing about $30 now (including the exorbitant shipping rate I paid to get the transmitter). I think something like this is a good investment for anyone who likes to do their own tuning.

Kyle: I have thought about implementing some sort of a crossover, but first I need to get the sensitivity adjusted right and get rid of the interference I'm getting.

Mgro: My motor did not come stock with a knock sensor and I'm afraid the heat will eventually damage the mic if I permanently mount it to the motor. There is a real nice place towards the top of the block on cyl. 4 where the clamp fits, so for now that'll work.

 

do you pick up any engine noise or any other disturbances? Basically how do you differentiate between what sound sliek detenation and anythign else...

 

I just barely finished this, so I haven't had too much of a chance to test it out. My idea for this is based on this:http://www.autospeed.com/cms/article.html?&A=0353
Like I mentioned before, I am picking up a little bit of interference (Have you ever hooked up an amp or deck and you get some alternator whine? It's kinda like that) I think with a little bit of trial and error I will be able to distinguish the sound of knocking.

 

You could (assuming you have an aux input on your radio) save even more money by omitting the FM Modulator. Better sound quality too. Interested to find out how it works

 

also, if you had it permanantly attached to your block, i would think the hot glue would probably not be the best form of adhesive... it would probably melt

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StrangerWitCandy &raquo;</TD></TR><TR><TD CLASS="quote">also, if you had it permanantly attached to your block, i would think the hot glue would probably not be the best form of adhesive... it would probably melt </TD></TR></TABLE>

haha, yeah probably not. It already gets kinda soft on that clamp.