Ignition knock detection method?

[CHB]

i guess everyone that tuned their programmable EFI on chassis dyno knows the dyno operator normally has a device that allow him to "hear"/detect ignition knock. my question is at what frequency of the knock signal normally occur?
i don't have much idea about this so please help me to clarify my doubtss....

[jezza323]

the frequency differs from engine to engine

[ed]

...everyone...knows the dyno operator normally has a device...

usually called ears

[CHB]

the frequency differs from engine to engine

do you mean number of cylinders?

[amichie]

It depends mostly on the bore diameter.

[Chrisso]

I saw a thread a while back (not sure if it was here or somewhere else though) where a guy had used the Jaycar super ear kit and recorded the signal on his laptop then analysed it with music software. Essentially he was able to clean up the signal and see the frequency for his engine. I believe he overlayed rpm datalogs but I might be making shit up now.

[CHB]

from autospeed article, it mentioned that frequency =900/(3.142*bore) where bore is in meter. how true is this?

[mikie]

well theres no real way of telling without testing. you would need someone that knows what they are listening for or a knock link, as well as the recorded signal, then filter out all other frequencies according to the formula and parry them up. iv been trying to find plans for a diy knock link. anyone know of something???

cheers Mike

[thechuckster]

Bore diameter, cylinder spacing & crank pattern, chamber shape, etc all contribute to identify knock frequency. Rpm, load and valve train noise also contribute to the difficulty of detection.

This guy from the MSEFI forums - he sells a kit that's supposed to be fairly useful.


re: Chrisso's post, I think that was Chris Davey as I built him a jaycar "super ear" kit.

[mikie]

ok silicone chip have a knock kit available, but only for their ignition comuter, but it does seem to have been tuned in for around 6.5Khz as the detection frequency. so for the 3sge being a 6.66Khz acording to the formula seems more or less sot on to me.

Cheers Mike

[JP]

I've got some old toyota TCCS training doco's here and they state 7Khz, but dont state what engine that is for

[c2888]

i found this whilst surfing some honda forum (apparently they have a hackable ecu and everyone and their dog are tuning in the us of a)

DET CANS

http://forums.neons.org/viewtopic.ph...&highlight=det

it's so simple, why nobody has thought of this before, forget your electronic dodads, this is the way to hear knock/det/ping/pinking

[mikie]

hahaha thats gold, good find

if we have a freq. to filter too, what about a low and hi pass filter in series with a preamp???

Cheers Mike

[wombat]

Lost of places would use something along the lines of the Wolf system.

http://wolfems.cart.net.au/cat/2007627.html

Basically its headphones on a knock sensor (I know there is more to it than that, but thats what your end result is).

I'd say lots of places would have this or make thier own or a different brand.

Side not if you read in the description its a high quality affordable tool. lol at $825 for the cheap one.

Check the site cos it has some sounds and videos so you can hear what it does, very distinct noise when its knocking.

[mikie]

yeah seen those, all it is is that i described above. it filters out everything below and above a certain range, then amplifies the signal. not worth $800+. Modifying the super ear would probly be the better/cost effective solution for an enthusiast. my 2C.

Cheers Mike