DIY knock detection, how?

[eliot]

stevieturbo said:

eliot...could it be triggering like mad because it is actually hearing things ??

Just revving it hard in the drive way makes it trigger like made though.

If it was truly knocking that much, surely i would of killed it by now after around 300-500 miles of driving. Spark plugs look fine.

I could try 15' of advance anything over 100kpa just to proove it i suppose.

[stevieturbo]

Some sensors are very sensitive. They can pick up bumps in the road, noisy lifters/tappets, piston slap....

Thats why knock sensors arent always the most reliable thing to use.

using our ears, we can filter these things out from knock, when we actually hear it, which is why the det can method is regarded as the best.
Be they ear muffs with some tube attached to the block, or the tin can method mentioned ( interesting that one )

Not much point monitoring with something, if you dont believe it when it says it hears det/knock.

[daxtojeiro]

Elliot,
mine is fine untill 4500rpm when the valve gear makes so much noise it triggers it, but thats OK with the megasquirt code as I made it so it had a rpm limit to when it reacts to the input, I set it up by tapping it with a small hammer, seems to work OK. Anyhow, the sensor is off a Saab, theres loads of them in scrap yards. The only real way to do it is to have the analogue output from the sensor go into Megasquirt and datalog the input and then make a matching map, so if the input is around say 2V at 4500rpm and 1V at 2500rpm then only retard if you go above that, not 1.5V over the whole rev range, the trigger really needs to be increased with rpm, it will come eventually, wait till me and James start on MSII
Phil

[GreenV8S]

Perhaps it would be possible to look for a rate of increase of noise rather than any specific noise level. I guess that's what the trained ear would do?

[eliot]

Im definitely getting knock today as i can hear it (light comes on too). Not helped by std petrol and might just have something to do with the inlet temps hitting 100'c
Really need to look at intercoolers.

[GreenV8S]

stevieturbo said:

Bosch sensor that comes with the Knocklink is 0 261 231 006 Single 8mm hole with 2 pin mini timer plug.

I've got one of these on order, £30 from my local Bosch agent. I was afraid it was going to be quite a bit more than that.

[eliot]

I scored this one of ebay the other day, before you lot spotted it!
http://tinyurl.com/deopg

I'll let you know the results when it turns up.

Eliot

[jaycos]

hi folks i know this is a old post but any room for a newbie im new to all this tuning ect , i have a 2wd 88 cossie on dta p8 management and im ok with tuning a fuel map but im a little baffled to say the least with ignition i currently have a copper tube in the middle of my inlet firm hose into the car glue into ear defenders . Im not sure what im hearing to be truthfull and i was wondering would i benifit from buying a knock device with a display so i can see whatim hearimg if you know what i mean

cheers jay

[eliot]

I gave up with the Knocksense unit on my chevy, it couldn't detect knock over all the other clatter. Having read this article at autospeed:
http://autospeed.drive.com.au/cms/A_0

I made my own improved "stereo" version using This Maplin Kit

Which looks like this once the microphones are extended onto a pair of croc clips:


I then use a pair of in-ear earphones with a pair of ear-defenders over the top of them so all you can hear is the engine through the microphones. The great thing, is that it DOES actually work - there's alot of clatter and noise, but you can hear the knock amongst the noise - the only problem is that dynamic range tapers of a high rpm and it gets harder to detect things.

Eliot

[cptsideways]

I'd like to have something on my car, the idea of having a warning light is very appealing as I'm often otherwise occupied when caning living death out of the poor old engine

My Toyota 1G engine runs twin knock sensors as Standard (1988 vintage!) so wiring into these would obviously be a good option. For tuning purposes a plug for a microphone sounds like a good idea & the warning light for when I'm occupied.

I'd be very interested in a little kit to build up

[jaycos]

eliot said:

I gave up with the Knocksense unit on my chevy, it couldn't detect knock over all the other clatter. Having read this article at autospeed:
http://autospeed.drive.com.au/cms/A_0

I made my own improved "stereo" version using This Maplin Kit

Which looks like this once the microphones are extended onto a pair of croc clips:


I then use a pair of in-ear earphones with a pair of ear-defenders over the top of them so all you can hear is the engine through the microphones. The great thing, is that it DOES actually work - there's alot of clatter and noise, but you can hear the knock amongst the noise - the only problem is that dynamic range tapers of a high rpm and it gets harder to detect things.

Eliot

cheers Eliot for your speedy reply guess what im doing this afternoon we have a new maplins store here :d

cheers jay

[stevieturbo]

Jay...

I tried the electronic one Autospeed did ages ago. And to be honest, it picked up a LOT of background noise.

The tube/ear muffs is a lot quieter in that respect.

If you want to hear what detonation sounds like....Add one random timing figure into your full load map.
Gradually increase this until you hear it. TBH Cossie engines are pretty audible vie the ear without tools anyway.
Obviously there are tisks there....

So if you can make your engne "pink" under light load, by screweing the advance forward there...same sound. At least it will give you an idea of what to be listening for via the headphones.

It will sound like a fairly flat tick/splat via the head phones...Its weird, as it sounds so different in the car with your ears.
Ive also found its much better to listen as a passenger, and not as the driver.
Driving takes away too much concentration, at least until you are confident with what to listen for.

Or find a scrap old car where you can wind the dizzo forward til you hear the pinking etc

To top it off. Ive heard Link's new Knock Block device. Kit is apparently vey good. Never used it myself though.

What sort of peak timing are you running Jay ?? Mates car is down to about 12-13deg at 25/26psi, and its quiet at that with SUL fuel ( we dont get Optimax here )

[eliot]

stevieturbo said:

Jay...

I tried the electronic one Autospeed did ages ago. And to be honest, it picked up a LOT of background noise.

Do you mean electrical noise or just mechanical clatter? - yes there is alot of clatter, but ive tried it on the chebby v8 and a griff 500 and you can pick out the noise.
Your right about getting a passenger to use it, leaving the driver to drive!

[stevieturbo]

Mechanical clatter.

Damn engines are noisy !!! Although that engine might have had Rhoads lifters too.

Though when I look back....the detonation was quite apparent. I just wasnt sure what it was supposed to sound like via the electronic amplifier at the time !!!!
It was so unfamiliar, I thought it was something else.

[jaycos]

hi stevie heres a short avi of det amplified

http://media.putfile.com/knock-73

Edited by jaycos on Sunday 5th November 15:29

[stevieturbo]

Sounds weird on these speakers.

Not like what it sounds via my ears with the stethoscope.

Anyway...if its detonating that much, get it sorted !!!!! I expected the odd few blips...not a sustained attack lol

[jaycos]

its not my car mate just a file i found lol

[eliot]

Which bit is the knock? - In the middle of the clip the knock / fart type sound, sounds very severe if it is knocking.(sounds more like Interference)
After that bit, there is a squeaky high pitched noise - which is the noise ive heard on mine.

[cptsideways]

I like the idea of a det can system, maybe route some pipe into the cockpit with a gaugepod hole with a little mini megaphone on the end nice & simple & effective. You can always plug it up for normal driving situations.


Off to the shed for some bits & bobs

[vixpy1]

I got my electronic ones off a chap in sussex, about £60 without the knock sensor