Adding knock sensor to AEM EMS
 

I have a 30-1710 AEM EMS I am having someone help me set up a wire harness for my engine for it and I would like to add a knock sensor eventually. I looked at the PDF file for the EMS and it mentions one pinout for a knock sensor but I wasn't sure what i need to do to wire one in and what would be a good one to use. If anyone can give me some wiring advice for it and if i should look for a stock miata one from a certain year or some kind of aftermarket one that will work with the miata.

Search for one sold by Boris. It's called Knocksense. It'll do the job. You'll have to fine tune it.

Engine knock detection and indication for all vehicles is this the one? while i was previously searching the knocksensems was the onely one i saw come up and a lot of times complaints were associated with those discussions i believe you even posted saying you weren't impressed with its efficiancy. So is this a waste of time? is a knock sensor in general a bad idea? I didn't look into the knocksense before also because i assumed the ms on the end meant it only worked for the megasquirt not the AEM EMS also

That's the one. It takes time to fine tune it. It's not put it in and forget about it. You have to tinker with it after installing it. Ask Savington; he dialed his in pretty well.

The AEM will recognize it.

You can use a saturn knock sensor for the EMS. Search the AEM forums for details. You have to run a shielded wire to the sensor and mount it to the block using a modified bolt. I've got one installed but I haven't got it working real well yet.

No, you can't use that (it can't interface with the EMS) and it won't do the job reliably either.

+1. The resonant Saturn sensor is the one he needs.
Flat response sensors won't work.

Do not use that. You don't need to buy this device because it can't interface with the AEM EMS. You'll be wasting your money.

I am using a flat response (bosch?) knock sensor on my aem ems and it does work. Not ideal due to the low voltage but it does work.

It's a leftover from my link ecu days.

I looked through the aem website searched miata nock sensor / saturn knock sensor / and nock sensor couldn't find any info though. when adding the wire or wires into the harness for the knock sensor do i add only one or two? The AEM single Pinout do i run one wire from there only or do i add a second "ground" wire to the aem pinout somewhere also? and honestly which one would be best for the knock sensor a wideband bosch one or that saturn one (and if i get the saturn one which engine is it from?) one i get it done i'll post most info and a howto (this could be a while though since I still have a decent amount of work on the car to make it run)

Yeah, I used one with my AEM EMS (Bosch one which came with my Knocksense back then) too, but it was giving false alarms - maybe my car is noisier (maybe because of the supercharger whine). The Saturn one works better. The reason is unlike the Link, the AEM EMS doesn't have a built in bandpass filter so you even strong non knock frequencies are seen as knock from the ECU.

Check BarryK's post in this thread - it has the part number:
MX-5 Miata Forum - Who's running a knock sensor with the AEM EMS?

You can get the connector either from a GM car in some junkyard, or order one along with your sensor from places like www.rockauto.com (that's where I got both my sensor and connector from there)

I use a shielded wire for the signal. If you do too, connect only one end of the shield to chassis ground. Besides that, the connection sensor to EMS is just one wire.

Which is also why the AEM EMS only looks within a certain amount of degrees from a spark event to register it as knock, to attempt to cut down on false triggers. Again, technically not the most ideal but still pretty slick and better than nothing at all.

Knock should be louder than anything else around a timing event.

I think i found the knock sensor... it is the one for 1991 - 1995 Saturn SC and SL as well as the 1993-1995 SW series. now to figure out how to weld a nut onto the cylinder head if i read his instructions right. I really don't need the knock sensor yet but i'm still going to look into the stuff for it if it isn't too pricey i may go ahead and buy it and install it now so that by the time i get the turbo added to the car the knock sensor will already work

I bought the nut from the local hardware store then brought it along with the engine mount bolt to the exhaust shop around the corner and they welded the two - they didn't even charge me because it was like a 2 minute job (I just tipped the welder)

Can one use the one that FM sells?

BTW j_man; I stand corrected on the knock sensor. I just reread the thread on m.net about the subject. This is the second time you suggest it to me and I simply forgot. That's what old age does to me!

you put it on the engine mount rather than the cylinder head?

FM's goes on the engine mount. All knock sensors I've seen in OEM apps go on the engine block, not the cylinder head. I haven't seen much though.

If you put it in the cylinder head you'll encounter a lot of interference from valve noise.

so it either goes on a particular mount or it goes on the engine block... i need to find a miata i can look at

Nope. I have that adapter (from the Knocksense times) too but it doesn't fit the Saturn sensor thread.

No worries. I forgot that I've told you too :)

I just used the engine mount bolt which is easiest to access from the passenger side wheel well. Just remove the wheel and take a look - one of the bolts is visible right there.

Then I'm screwed because that's the one currently in my block.

What are my options? I read you went to some hardware store and bought something and had it welded. I just didn't understand what.

To the op: sorry for threadjacking

edit: I just saw your post. You mention a nut. (I guess I'm the nut in this instance).

You buy a 10x1.5mm nut from your local hardware store (the Saturn sensor, which is threaded, can bolt in that nut). Then you get your original motor mount bolt along with the new nut to a someone with a welder and tell him to weld the nut to the bolt head. And you end up with a mounting block for your new sensor :)

Many thanks! :bowdown:

will that work for an engine mounted transverse like in the AWD and FWD car? Which motor mount do you hook this on to?

Project; I don't see why not. j_man makes his suggestion about which side in our motors just based on the one that's easier to get to. Just look at your engine and hook it to the one that's easier to reach.

my only engine mount that attatches to the block is the passenger side mount, i'm kind of confused how attaching the knock sensor to the mount will allow it to read knock inside the engine doesn't the end of the sensor actually have to touch the block?

I'm currently running the same exact set up. I believe the Links Bosch sensor is the same pn as used on the buick grand national among many others. On the Link the signal was beautiful and precise, on the few data logs I got b4 the i/o went out.

Now on the AEM EMS I've yet to see a signal above 0.99 volts. I've even started up the logging and started banging stuff with a hammer just to see what would get recorded. Still nothing above 0.99 volts. I thought this was a 5v sensor? Right now I just consider anything above 0.3v is probably real knock, and I've got my timing WAY retarded.

I'd like to have a knock function that I actually have faith in. Would an external bandpass filter help to get the old Link/Bosch/FM sensor to log like it used to on the Link? Is there any advantage to buying the "7 khz sensor from the GM Saturn, part number 21021879"? Should I rescale the sensor table in the AEM EMS from a 5v to a 1v?

I saw that 'JasonC SBB' mentioned a bandpass circuit, does anyone have the link?

I didn't know you could rescale the sensor table to 1V, if so that's a good idea. It's not a 5v sensor. I think my cal table has knock defined around .3volts at normal rpm. I took a quick look at it before emailing it to Sav. But just sitting there idling the volts are very very low.

I'm going to give this a try.

Attachment 201814

I havn't been able to rescale the volt axis from 5v to 1v, but using auto expand, with knock volts in its own plot in AEMLog works just as well for viewing at least.

I just ran a search and found it here:
https://www.miataturbo.net/forum/t31284/

thanx jman!