DIY knock detection, how?

[GreenV8S]

As far as I understand it, knock detection systems typically consist of a piezo microphone bolted to the block, a band pass filter and some sort of adjustable level detection circuit, all built into the ECU.

What I want is a standalone version that can be fitted to a vehicle that doesn't have the necessary smarts built into the ECU. Either just to display a 'noise' reading that I can look at during testing, or ideally with some sort of alarm output. I've found a couple of people selling diagnostic units for around £250, look like they're aimed at dyno operators rather than something intended to fit a car. Is there a better solution?

[dilbert]

How about the Mk I earball.

[GreenV8S]

Eh? What's that you say? Speak up would you?

[cyberface]

dilbert said:

How about the Mk I earball.

You got funny shaped ears, innit?

[deltafox]

How about an audio amp and a set of headphones so you can hear it?

[daxtojeiro]

Hi,
there are several methods of doing this, I have designed a system for Megasquirt that works with the Extra code : http://megasquirt.sourceforge.net/extra/knock.html but if its indication your after then theres this: www.viatrack.ca/
Phil

[eliot]

Ive got one of Boris's knocksense units on its way to me right now.

[Boosted LS1]

Peter, I made some using a piezo and a bespoke circuit board with a volume and sensitivity circuit plus a red light. I'll see what parts I have left. I may have the schematics somewhere.

Boosted.

[350matt]

A rather bizzarre and very cheap method is to run some relativly solid plastic tubing onto the engine ( like onto the end of a stud) and the other end goes into the cabin / outside the test cell and is attached to a large open ended tin can with a pipe soldered to the bottom to fix to the other end of the pipe. The pipe is drilled through to give a hole into the pipe from the can base You can then hear det usually as a sharp crackling noise.

We used this at Cosworth a couple of times would you believe

Matt

[GreenV8S]

Thanks for those links.

I've looked at the MegaSquirt info a couple of times and keep coming away unsure whether it capable of doing all the things I need. For example there appear to be multiple hardware versions but the Extra features that the knock detection system is built on don't work on the newest hardware?

Is there an advocacy forum or other resource where I can find out which (if any) MegaSquirt solution fits my problem? (essentially 8 cyl sequential FI, mapped ignition, mapped WI, dual lambda control)

[daxtojeiro]

Hi,
the Extra code will only work on the original MS microprocesor, not on MSII. MSII is simply a plug in pcb that replaces the original processor. Both work on the same pcb. Both have mappable spark, fuel and dual ego support, but the extra code has been developed for some time, it now does a lot more than just fuel and spark, it will do water injection too, have a look here: http://megasquirt.sourceforge.net/extra/
neither system does sequential, that is a subject that keeps coming up and no one has bothered with it that I know of, as it just doesnt seem worth the hassle. Maybe MSII will go that way, Ive no idea,
Phil

[Boosted LS1]

Boosted LS1 said:

Peter, I made some using a piezo and a bespoke circuit board with a volume and sensitivity circuit plus a red light. I'll see what parts I have left. I may have the schematics somewhere. Boosted.

And I can plug in headphones

[stevieturbo]

Autospeed did a couple of articles on making a knock detector, basically using a hearing aid amplifier, and you attached a small mic to the block.

Picks up all sorts of weird and wonderful noises though.

Knocklink can be found here, or indeed Im sure plenty of other palces sell them, and is basically the type of thing you want.
www.brdevelopments.com/link.html

Or det cans as some call them, with a piece of tubing attached to the block, then routed into a pair of ear muffs is supposed to be a very good way, although Ive never tried it myself yet.

[Pigeon]

You want a bandpass filter centred on 5kHz - apparently that's where the knock signal is strongest and most distinctive. (I got that from some SAE paper on ignition timing, so it's probably pretty good.)

[GreenV8S]

The link system looks very interesting and I may well give it a try. These systems all seem very expensive though given that one 'bar' from a graphic equaliser display does more or less the same thing.

[rev-erend]

350matt said:

A rather bizzarre and very cheap method is to run some relativly solid plastic tubing onto the engine ( like onto the end of a stud) and the other end goes into the cabin / outside the test cell and is attached to a large open ended tin can with a pipe soldered to the bottom to fix to the other end of the pipe. The pipe is drilled through to give a hole into the pipe from the can base You can then hear det usually as a sharp crackling noise. We used this at Cosworth a couple of times would you believe Matt

Fantastic I know money was a bit tight

[Marquis_Rex]

Marquis has allowed me to write this on his behalf so don't blame him....

Use a knock sensor bolted to a spare boss on te block, cur the wires and either wire drect to a set of stereo headphones, or into one of those CD to tape converters and you can listen to the 'knock' diretly, you soon get used to what the engine normally sounds like and then what knock sounds like.

The headphones may end up a bit loud or a bit quiet (usually work OK though i've listened to lightweight K's and clunky colognes among others) but using the tape adapter you can adjust your stereo volume to suite!

Learnt this at Cosworth Tech and used it on my own projects with some success ......

FBA2933

[stevieturbo]

So you are saying this works, with no form of amplifier at all ?

Headphones wired only of a knock sensor ??

[Marquis_Rex]

He says "Yes"!

[eliot]

My Knocksense unit turned up from Boris today, took a few weeks.