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Old 06-07-2012, 01:51 PM   #1
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Default Knock or harmonic/resonant "noise"?

(Preface - I’m using a DSM ecu/knock sensor which has built in knock monitoring and timing retard and I am logging/tuning with ECMLink. I can post a log and you guys can download the software from the link in my sig to read the log if you’d like, but it’s probably not necessary for my question.)

Have not found anything specifically related to this by searching.

Now that I’ve gotten a new clutch in I’m retuning for more boost, and in the process finding that there is a small amount of knock registering around 3700, 4600, 5800, and 6600rpm, and it tends to occur at/near those RPMs regardless of what I’m doing with the gross (not load referenced) fuel and timing adjustments. I am wondering if those are areas of some sort of resonance or harmonic weirdness with the 1.6L. It’s not strong enough for me to worry about, and I can get in there and remove it in the load based maps, but if it’s a typical harmonic/resonance that you guys are seeing too then I’m not going to sweat it.

Do you guys who have used det cans or otherwise monitored knock while tuning see it at regular locations, or is it all over the RPM range as one might expect (being fuel/timing dependant)? Just curious as I’m now trying to refine the tune as much as possible, and this is my first real attempt with this motor.
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Old 06-07-2012, 05:06 PM   #2
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I haven't noticed knock noise to appear at specific RPMs like that.

What bore diameter is the DSM motor that that ecu/sensor is from?
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Old 06-07-2012, 05:58 PM   #3
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85mm bore
88mm stroke
1997cc

Original engine is a Mitsubishi 4g63. Factory knock sensor is located roughly between cyl 2&3, at about the midline of the block. I've got mine in the lower intake mani brace hole on the Miata...probably a bit far forward and low but it fit so I went with it.
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Old 06-07-2012, 09:32 PM   #4
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Can you use an adapter to screw into the factory knock sensor location?
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Old 06-07-2012, 09:36 PM   #5
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when we all installed adaptronics just about everyone was getting a big knock spike in the 4500rpm region (iirc), it happened no matter what, and we agreed that it was just noise.

I wouldnt be surprised if the 1.6 has more of said noise.

Not many around here monitor knock on a 1.6
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Old 06-07-2012, 09:44 PM   #6
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What sensor and where mounted?
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Old 06-07-2012, 09:45 PM   #7
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stock both
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Old 06-07-2012, 09:55 PM   #8
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Quote:
Originally Posted by JasonC SBB View Post
Can you use an adapter to screw into the factory knock sensor location?
I was under the impression that the B6 didn't use a knock sensor. I'll see if I can figure out where the B6T had one installed.

Edit, looks like it's way up high on the intake side of the block. I'll have a look at my car and see if the boss is there and tapped:


Quote:
Originally Posted by 18psi View Post
when we all installed adaptronics just about everyone was getting a big knock spike in the 4500rpm region (iirc), it happened no matter what, and we agreed that it was just noise.

I wouldnt be surprised if the 1.6 has more of said noise.

Not many around here monitor knock on a 1.6
OK, thanks. And yeah, it seems like across the board it's only listened to with det cans during tuning, worked out, and pretty much left alone thereafter. Although I see that there's a new addition to MS that will monitor and pull timing.
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Old 06-07-2012, 10:04 PM   #9
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Looks like the boss may be there and tapped already based on this photo from crowder92's build thread (he states he used a B6 block).


And my sensor looks identical to the one in the above B6T photo so maybe it's threaded the same way. If so, I'll move it and see if my readings change.
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Old 06-08-2012, 02:52 AM   #10
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Sender w no lead is oil switch.
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Old 06-08-2012, 11:34 AM   #11
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Yep, that was on the pic already from the Protege forum where I copied it Thanks though.
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Old 09-17-2012, 02:36 PM   #12
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Update and more questions.

I have up until this point resigned myself to either low boost or low timing advance in order to deal with the knock I opened this thread about. I get really frustrated seeing that everyone else here is running 5*+ more advance than I am under load, then periodically go out and try to tweak my tune again to no avail. I have not moved my knock sensor to the stock B6 location, as I've not wanted to put my stock oil pressure sender on a Tee or long adapter which is what I need to make it fit.

Then I was reading through the knock article that Jason linked to in this thread and learned that there are two types of knock sensor, flat response and resonant. Looks like I probably have a resonant type, which was likely tuned for the 4g63 it originally came out of. Now to find out if I can still get a 323GTX knock sensor, and if it will work with my ecu.

I continued reading and stopped at this phrase:

Quote:
some burst knock with quick throttle application
I am getting this with my car and am having a hell of a time dialing it out. On an upshift from 2-3 or 3-4, I get a huge spike in knock within about 0.5sec in a load area that typically causes no issues if I'm just accelerating through a given gear. It may of course be related to the knock sensor issue, but after searching the net a bit I see that it is not too uncommon.

I see that my "burst" knock coincides with higher than normal AFRs directly after an upshift. I can adjust TPSDelta to give a bigger squirt of fuel based on how quickly the throttle moves, and after playing with that yesterday it did not help. And if I get out and back in quickly, the knock minimizes or disappears completely.

Has anyone dealt with this problem in the past?
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Old 09-17-2012, 09:47 PM   #13
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99-05 knock sensors are broadband.
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Old 09-25-2012, 03:50 AM   #14
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Got this figured out for now. Was able to reconfigure my airflow settings in a way that cures all but a small spike in AFRs which does not create any knock. Kind of a bandaid method, but it works so **** it.

Also turns out that my knock sensor is a flat response/broadband type, according to my engine management's software developer, so I'm not going to worry about that part of the equation any more.
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Old 09-26-2012, 01:39 PM   #15
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"airflow settings"?
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Old 09-26-2012, 06:14 PM   #16
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Were you able to add in the timing you were expecting? I just installed my sensor/board in my MS3. I'm hoping to be able to add a little more in up top.
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Old 09-26-2012, 06:25 PM   #17
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I'm guessing the knock sensor hasnt been programmed to the engine. I forget which ecu I was dealing with at the time but one of them required you to go through a convoluted set of operations in order for the ecu to learn what the engine sounds like without any knock so that it can properly filter out false knock.
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Old 09-26-2012, 06:58 PM   #18
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Quote:
Originally Posted by djp0623 View Post
Were you able to add in the timing you were expecting? I just installed my sensor/board in my MS3. I'm hoping to be able to add a little more in up top.
Don't expect too much above 5500-6000rpm due to noise.
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Old 09-27-2012, 12:13 PM   #19
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Quote:
Originally Posted by JasonC SBB View Post
"airflow settings"?
Yep. The ECMLink software I'm using with my ecu (from a Galant VR4) allows both MAF and speed density operation, and a blend of both as I just learned. I'm operating in speed density and as such typically have the MAF adjustments cancelled out (these adjustments act like an SAFC would). I had a look at my logs and figured out what Hz range the “MAF” was in (only an educated guess by the ECU since I’m not using one) during the lean spike, then enabled the MAF compensation table and played with the settings there so that the ecu thinks I'm getting more air than I actually am, and therefore dumps more fuel in. I have tried to do this very thing in my VE table, but there’s some overlap in load cells between this lean spike and a steady pull, and after playing with them I was still unable to get it sorted. I still need to clean up the VE table in other places now that I’ve dicked around with the MAFComp settings but I can live with that.

Quote:
Originally Posted by djp0623 View Post
Were you able to add in the timing you were expecting? I just installed my sensor/board in my MS3. I'm hoping to be able to add a little more in up top.
I did add up to 5* before peak boost, and a couple degrees after. I still have the lowest timing after peak boost than any map I've seen here, though (15*). I'm going to recheck base timing and make sure it's where I want it, then try again to add more in. I can’t seem to get above 16* and 13psi boost without knock showing up, which may be related to what Leafy is saying below.

Quote:
Originally Posted by Leafy View Post
I'm guessing the knock sensor hasnt been programmed to the engine. I forget which ecu I was dealing with at the time but one of them required you to go through a convoluted set of operations in order for the ecu to learn what the engine sounds like without any knock so that it can properly filter out false knock.
I will look into whether or not my software has a learning feature. I kind of doubt it though since I’m using an ECU from a production car and the knock sensor that’s native to it. Probably screwed there. I can raise the RPM threshold where the sensor is activated and if I can listen for knock with some det cans and confirm where knock is/is not happening I may raise it a bit. I can also turn it off, but that’s a last resort if nothing else works and the det cans don’t reveal any actual knock events.
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Old 09-27-2012, 12:25 PM   #20
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I'm kinda thinking your timing offset might be off and you're actually running more than you think. I've yet to see a car knock past peak with such low boost and low timing.
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