Cheap Knock Sensor Kit

[666DAN]

For those that like to solder!

OK Jaycar sell a knock sensor kit that is designed to interface with their ignition system (but the system starts to get expensive especially with the programmer etc etc)...but the output is luckily linear in relation to knock intensity; 0 -5v range. You can take the output of their knock sensor kit and wire it into their bar graph voltage display kit (set at 0-5v input) and you've got a nice visual knock warning with graduations!!!

All for under $40

[VB-]

looks promising, bu i wonder how accurate it is... nobody really seems to use there stuff though, so its hard to get a decent review. i've only heard of one or two people using the ignition system, one said it was quite succesful (LPG setup, but others said when you add up all the costs of various components, you can afford more of a known thing.

dont suppose it has any form of adjustment for frequency?

it will revolutionize the tuning world when someone markets a an actual monitor for knock that has capabilities to display a set figure/sign for knock, but this really doesnt do that.

ionization current ftw!

PS - for that money i'd make a set of det-cans, wayyyy more accurate adn reliable (providing you are)

Edited July 31, 2008 by VB-

[666DAN]

This kit listens between 4.8-6.4khz...it has sensitivity adjustment for eliminating background noise.

Yep I agree the full jaycar ignition system would get fairly costly, that's why I used the output straight into the voltmeter so I've got a cheaper interface.

Anyway I'll give it a go and see how it is.

[VB-]

definately keen to hear how it goes, as opposed to stethascope/det cans and even other forms of electronic knock detection is its available

[666DAN]

VB here's something of interest!

I've ditched the bar graph volatage display in favour of the >$8 multimeter Jaycar have. When you wire this up you now an output in Volts so can use that as your degree of knock; anything under 1.00V is safe, anything over needs attention

You basically free-rev the car, set the pot so free revving = 0.00v and it eliminates background noise, even a slight knock will spike well over 1.00v instantly as it's actively listening in that frequency range.

It works great and can all fit in a jiffy box with 3 inputs (knock sensor, 12V + & -) just have a rotary dial to set sensitivity and you've got an LCD display from the cheapo voltmeter, an accurate and sensitive det-box for $30!!!

[VB-]

but you'd still need to set it up using something more reliable wouldnt you? and if you have access to it why not just use it instead of building your own? unless your talking more for long-term install rather then straight tuning. in which case it sounds awesome

[KiwiRS4T]

For those that like to solder!

OK Jaycar sell a knock sensor kit that is designed to interface with their ignition system (but the system starts to get expensive especially with the programmer etc etc)...but the output is luckily linear in relation to knock intensity; 0 -5v range. You can take the output of their knock sensor kit and wire it into their bar graph voltage display kit (set at 0-5v input) and you've got a nice visual knock warning with graduations!!!

All for under $40

Looks interesting but how does it sense knock? What exactly is it measuring? Does it have a microphone listening for knock or is it measuring the vibrations causd by the knock or what? If it works I would be glad to buy one.

[VB-]

quality post ^

[Kinks]

VB here's something of interest!

I've ditched the bar graph volatage display in favour of the >$8 multimeter Jaycar have. When you wire this up you now an output in Volts so can use that as your degree of knock; anything under 1.00V is safe, anything over needs attention

Does the knock sensor do peak hold and for how long? If it peak holds for less than a second then you have no hope of seeing the result on your multimeter because multimeters are quite slow to react. For tuning a multi might be OK but for general road use a bar graph will catch your attention better and can be seen via peripheral vision. You have to look directly at a multimeter to read it properly.

Not a bad idea though. I would be tempted to use this kit with a PFC to cut ignition/fuel if knock was detected rather than flashing a stupid warning light and hoping you see it in time to save your engine.

[666DAN]

but you'd still need to set it up using something more reliable wouldnt you? and if you have access to it why not just use it instead of building your own? unless your talking more for long-term install rather then straight tuning. in which case it sounds awesome

Not really as once you've eliminated engine noise (background) over the rev range any slight knock will immediately shoot you straight over 1.25v anyway (that's the trigger frequency its looking hard for) So sticking to under 1.00v knock you know you're safe. I'm getting a max of 0.65v and there is not a hint of detonation, even that I could use as a yard-stick to tune against.

Would be good to put it on a car with a PFC and compare knock values though

[666DAN]

Does the knock sensor do peak hold and for how long? If it peak holds for less than a second then you have no hope of seeing the result on your multimeter because multimeters are quite slow to react. For tuning a multi might be OK but for general road use a bar graph will catch your attention better and can be seen via peripheral vision. You have to look directly at a multimeter to read it properly.

Not a bad idea though. I would be tempted to use this kit with a PFC to cut ignition/fuel if knock was detected rather than flashing a stupid warning light and hoping you see it in time to save your engine.

A capacitor and a diode wired on the output gives you peak hold ability

[maximajim]

Old thread

But does anyone know if this kit actually works with Nissan Knock sensors? I have a standalone that has knock correction, but the nissan sensors are too quiet.

[maximajim]

Well if anyone cares,

I've found the frequency for knock in a 86mm bore engine is about 6.7khz, which is a hair above the jaycars low pass filter. So out of the box you're not

getting the whole story. I've bought 2 kits to see if I could some way increase that low pass filter to about 7.5khz.

[VB-]

thinking more into it, i rkn the knock sensor itself will be more of an issue than the display. what sort of mods have you got maximajim?

[KiwiRS4T]

I am very keen to find an accurate way of detecting knock as I want to do my own tuning and have got a wideband kit but there seems to be no cheap solution. Guilt-Toy reckons that the PFC is too conservative with its knock detection but I don't know if that is a problem with the PFC hardware or software or the nissan sensors. He uses a K-mon knock detector with two special sensors (total around $1500) so I will try to get the answers from him.

[maximajim]

thinking more into it, i rkn the knock sensor itself will be more of an issue than the display. what sort of mods have you got maximajim?

I have the regular mods, greddy im, 760cc injectors and a custom 62-1 turbnetics turbo. I also have an AEM EMS standalone. It has knock correction with high and low filters. It is possible to add fuel and/or subtract timing in the event of knock detection. We can't always use det cans so in theory this system should work well.

Unfortunately it needs to be in a 0-5v scale and the nissan knock sensors don't suit it well enough. By using the jaycar kit with proper freq filters it should work very well.

[VB-]

kiwi: det cans

maximajim: would be useful but plenty of people dont use it and dont have an issue, just be a little conservative in the tune. in theory it all works well but i just cant see it coming together as your expecting it to. that said, you try it and let us know how it goes

i'm keen to find out, just not to be the guinea pig

[Equinox]

I've built one of these and hooked the output of it up to one of the inputs on my Lambda sensors data logging software.

Gone for a few runs and compared it to the PFC's knock level. The knock boards output seems to rise in volume directly in line with revs. Small spikes occur but you can see pretty clearly what is normal noise and what is abnormal.

Havn't had a chance to actually go out and make the engine knock to test it properly though. I'll report back when I do.

I'll also grab some screen shots of the logs off the laptop when I get a chance.

[VB-]

lol i wouldnt go out and diliberately make your motor knock just to test this thing out.....

[maximajim]

kiwi: det cans

maximajim: would be useful but plenty of people dont use it and dont have an issue, just be a little conservative in the tune. in theory it all works well but i just cant see it coming together as your expecting it to. that said, you try it and let us know how it goes

i'm keen to find out, just not to be the guinea pig

Well the boards should be here on Tuesday. But I have disagree, I'm sure with the a PFC or other [non-knock] standalone it would be pretty useless. But the EMS I have is fairly powerful, not only will it react to knock, it has the ability to ignore mechanical noise. All you have to do is pull timing way back and go for a test run, that will be your base line which will be in volts. Any voltage above that will be treated as knock, and the higher the voltage, the higher the timing retard and fuel addition. If knock sensor 1 sees knock, it will add fuel to cyl 1,2 and 3. Knock sensor 2 does the others.

That said, it's a really safety device, there are conditions on the road which can't be replicated on a dyno where the car is tuned.