Anybody ever put a scope on their knock sensor?

[Jasper]

Adobe Audition is free for a 30 day trial. I did have a go with that other program, but it's nowhere near as good.

Nyquist frequency is twice the maximum frequency of interest. For more info look it up on wikipedia. As long as you record above 25kHz it should be ok. Any lower and you will lose signal information. IIRC I used 40kHz+

As for your 6800Hz "resonant frequency" this may just be the frequency of maximum gain for the Toyota sensor we are using... Even if this is the case, Toyota would have picked them for a reason, and it is probably pretty close to what we want.

Anyone have a frequency response function/curve for Denso knock sensors?

[adamaw11]

Well I managed to get hold of adobe audition (trial), and it appears as though the frequency for my 4age seems to be centered around 8100hz, with the recording while driving (shown, greenish line through the centre) and also with the hammer tapping the block
I tried to run a bandpass filter thing, and it did something, just not what I was hoping.
I might be in just a bit over my head here, I'll just keep playing around a bit and see if I can filter out the sound at around that frequency

[Jasper]

What sampling rate did you use when recording?

[adamaw11]

I think i defaulted to 22 khz or something. It would happily convert to a higher sampling rate after recording but didn't seem to wanna actually record at say 44.1 khz I was just using the basic windows sound recorder, so now that I have adobe audition on the laptop I can do the actual recording with that and see if it works better....

Would 22khz actually be too low of a sampling rate?

[Jasper]

22kHz should be ok, but if you can go higher you might as well.

When I was recording mine, I changed the settings and saved a file. I made the recordings to this file and saved them under a different name, then opened the original file again to preserve the settings.

The reason I asked is you signal seems a bit light on high intensity in the upper frequencies, with no strong harmonic shown.

Seeing your signal reinforces my belief that these knock sensors are not the broadband type I referred to earlier. I think this type of analysis would work MUCH better with a broadband type sensor, I'll give it a go when I finish my turbo installation.

[adamaw11]

hmmm I thought I saw those upper harmonics at first, maybe what I posted was after I'd stuffed around with some filters.

any chance you could give more instruction about how you filtered out the knock events?
You mentioned "bandpass filter" I found that amongst the "scientific filters" and there were a fair few buttons and values to configure. I havn't yet been able to cleanly cut out the higher and lower frequencies either as you appear to have done.

I'm figuring I'll record some idling while tapping the block and see if I can filter that out for a start.

[Jasper]

My 30 day trial expired a while ago

If you post some screenshots of the filter menus I would probably remember, otherwise I will try to install it on a different computer on the weekend.

[adamaw11]

Filters menu I'm guessing.....


Scientific filter.... where it has a bandpass setting and a few configurable values


Dynamic eq which also showed 'bandpass' and I'm guessing could be used?


Its really quite beyond me still.

Oh and while looking for Audition in the first place, I found version 1.5 as well as 2.0 They are both a 30 day trial, and more-or-less have the same functionality afai-care but 2.0 is 470mb download and 1.5 is only ~47mb download. I can't see why 2.0 is 10x bigger. I'm just hoping once I've used up the trial of one I can install the other version.

[Jasper]

From memory, I used a Butterworth bandpass filter with a steep transition, ie low transition bandwidth. You should then be able to specify the attenuation in dB, rather than "Order", use a fairly high attenuation.

Could have been Chebychev 2 though...

[1jzracing]

[QUOTE=adamaw11]I'm sure some of you guys might know about the "super ear" kit from jaycar.
Well just yesterday I plugged my knock sensor output into my super ear as though it was an external microphone, and it worked to some extent.QUOTE]

i tried a similar set up with a small jaycar amp called a "champ" it was a whole $6 or so and to my dissapointment it wont run a signal straight from a microphone (which i epoxied to a big clip so i could clip to the block), it needs the "pre-champ" kit $7 which is a pre amp for a mic.

..... BUT when i tried hooking the champ directly to a knock sensor that was removed from the block it was SUPER SENSITIVE!!!! the slightest touch on the sensor with a screwdriver would near defen you unless it was turned right down

so im guessing this will make a great "electric ear" for tuning if i hook it straight to the knock sensor

ill do an experiment with my road car

[chris davey]

Just found this thread

Ok, I have a jaycar super ear kit like adamaw11 and I also have a knocksense which is similar to a knocklink ie. adjustable knock detector with output to LED and 0-5v datalogging output.

So I have some stuff that is required but I am yet to set it up correctly. Basically, I want to do what you guys are doing with the frequency recording to determine what is actually knock and then I will adjust the knocksense to that level.

So is it possible for someone to tell me in absolute laymans terms how it is done? I have super ear kit, 2 stock knock sensors that aren't being used, 1 bosch knock sensor, laptop (can download that software if need be). I suppose I don't actually understand how you connect to the lappy to record it?

[Jasper]

What ECU are you using? Does it have a spare analog input channel?

[chris davey]

I have a Microtech LT12s and AFAIK I don't have any other logging channels free. The knocksense is wired into the coolant temp sensor line and shows as a drop in water temp when knock occurs. Well that is how it will be but I want to be able to get the knocksense setup accurately first.

[Jasper]

OK, does your knock module have an output jack for headphones? If so, this is what you use to record the sound with your laptop's soundcard.

[chris davey]

I don't think the knock sense does but the super ear does so that must be how Adam was doing it. Ok, so just hook it up and off you go. Good stuff.