Knock Sensor Connected to LED
Turbo Mini Forums

Was thinking about connecting up a Knock Sensor to an LED on the Dash would be very helpful for mapping or just as a precaution.

Would it just be a case of making a little circuit so that the knock sensor triggers a 12v supply by using a transistor to the LED on the dash?

Just checking I have my facts right before I buy everything and find myself short with a pile of scrap wiring.

Thanks All

As I believe Dennis said, he found his ears to be a much better knock sensing device than any electronic device.

The knock sensor alone is not enough, if you mean just the bit that screws to the block.

Like a wideband sensor, it needs a box of electronics to go with it to filter and interpret the signal - the sensor itself is really just a high frequency microphone.

You can either rob the module from the doner car (if it is a seperate module to the main ECU) or there are a few DIY type ones available that work with common knock sensors.

ie, http://www.viatrack.ca/

Half way down the page, not the one at the top of the page - this one just happens to be listed in the MS-Extra manual, there are many others.

Schrödinger's cat - so which one am I ???

Hmmmm so does the time to make outweigh the befits?

you can make a home brew knock/pink detector. all you need is some copper pipe, rubber hose and some ear protectors

Edited by apbellamy on 28th Nov, 2010.

Personally, as Tom says (quoting Denis), you can hear it if you know what you're listening too. I know it well from my days with high powered Imp engines.

The use of a sensor and associated module is really only for feedback loops into ECUs to retard the timing IMO.

Schrödinger's cat - so which one am I ???

Rod S correct me if I am wrong but I was lead to believe that the signal from the knock sensor all be it a frequency produces a 5v amplitude which would be enough to trigger a transistor or is this after the module?

After the module, unless there are some fancy sensors out there with the electronics built in.

Which make of sensor are you thinking of ???

Schrödinger's cat - so which one am I ???

Bosch, but from what vehicle - the sensors are mated to a module or connect direct to the vehicle's ECU.

If there are any that have the electronics built in I'd need to do a quick check against a Bosch part number.

Schrödinger's cat - so which one am I ???

right now i don't really know because it was a plan on paper i was checking with the electronic smarts on here that i had my facts right.

Will do some research into if there's a knock sensor with it built in.

would probibly be a golf or polo something findable in a scrappy.

I used to use a mechanics stethoscope extended into the cab. I don't find it much use as it's not very clear over the sc box. Ive just fitted a egt gauge though to get around the problem.
Ron

there wre two types of knock sensors, resonant(like older toyota), and non-resonant (i.e. bosch).

the frequency of knock is engine dependant, main variables are cylinder bore and block material, but there are many other things to consider. Put simply any knock detectign device needs "tuned" to a particular engine.

the resonant type of sensor has a mass and a spring, at the tuned knock frequency the mass resonates, this gives an output which can be vuewed with a simple transistor/LED. This style of sensor has never been fitted to an a-series, so you cant get one.

a non resonant sensor requires electronics with a bandpass filter at the tuned frequency, and a noise filter, that can then display an output.

trouble is both these setups become useless on a noisy engine (and the a-series is a noisy engine!) above 4krpm or so. and where would damage most likely occur? above this threshold :)

if your good with mathlab i had some success runing an FFT on a bosch sensor signal then processing itto output above a threshold, should only require a laptop to give you a proof of concept, but by the time you perfect it you will know how to listen for it :)

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

so in short its rediculously complicated it would basicly meen making a new knock sensor, finding the frequency the a series knocks at and then program it then connect an LED to it :/
or the light will stay on perminantly?

it would therefore be easier to learn what to listen to.

there's lots of good reading on the internet on the subject, i think auto-speed maybe even had some simple demo circuits to filter the noise. if your a-series is all-helical gear boxed and belt drive on the cam, you stand a decent chance of getting it to work.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Thats a no for me then haha.

Type KnockSense into your browser. Imported mine from the US when I was building up my Megasquirt.

It's a small amplifier box with an output that goes to the ECU and an LED on the dash which I have on the van. It works on mine to retard ignition and can also be used to fire my water injection pump and pulsed water injector solenoid. Cost me about £24 I think.

PM me if you want further details. Most of the diagrams and wiring are available through Phil Ringwood's website; www.ExtraEfi.co.uk

Cheers

Richard

Edited by turbominivanman on 29th Nov, 2010.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Robert uses some sort knock light can't remember the brand though!

All modern Bosch knock sensors are the same. 15khz bandwidth. They only differ by the connector and wire length.
All you need is an old walkman. Open it, disconnect the reading head and solder knock wire instead. It's better to have a potentiometer between the sensor and the walkman input to adjust the signal strength.
Your ears are a much better signal processor than any electronic stuff.
Knock is most dangerous at low RPM way below 4k, so it does not matter engine is noisy above (most of engines are too noisy above 5-6k).

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm