how to desensitize a knock sensor?

[GreenV8S]

Now I've finally got the knock sensor wired up I'm getting false knock signals all over the place even with the sensitivity turned right down.

I guess the sensor is too sensitive for the amount of engine noise.

Any thought on how I can desensitize it? It's an ordinary knock sensor (piezo-electric I guess) bolted on the front of the head. I'm wary of trying to mechanically isolate it because I have no idea what that would do to the frequency response. That leaves some sort of electrical approach. Any suggestions?

[oakdale]

Isn't it more usual to fit knock sensors to the centre of the cylinder block a bit above halfway up?

[GreenV8S]

This was a lot more convenient!

[cptsideways]

GreenV8S said:

This was a lot more convenient!

It'll be getting excessive valve train noise in that case

[oakdale]

cptsideways said:

GreenV8S said:

This was a lot more convenient!

It'll be getting excessive valve train noise in that case

And positioning it centrally on the block means it senses from more than one cylinder.

[eliot]

Which one are you using?
I've got a Boris Knocksense and its useless. Even "knocks" when cranking the engine over.

[ringram]

late model lsx engines locate them low mid block near normal engine mount position.

There are loads of tables to "tune" them with regard to signal. each cylinder has a different noise signal etc.

Do they need to be bolted, or can you screw them in? MAybe with some thread seal tape..?

Or get something to tune them up better..

Or finally tune for mbt and dump them altogether

[Boosted LS1]

Knock is actually resonations in the block casing caused by detonation in the combustion chamber so I'd mount it in the block, somewhere mid engine and halfway up the block as that's where the vibrations will be felt. Is your block cross bolted, if so why not try the rover sensors?

ETA, also knock only occurs within a certain frequency so moving the sensor would be preferable to desensitizing it.

Edited by Boosted LS1 on Sunday 14th December 20:39

[spend]

I thought one of the drain plugs was a common place if you don't have the tapping on the block?

[GreenV8S]

I was hoping for an easy solution, but it looks as if I'll have to get off my ar$e and move the sensor.

[stevieturbo]

Or it could be the method of detection...some sensors are more senstive than others.


LSx sensors are VERY sensitive.

[oakdale]

GreenV8S said:

I was hoping for an easy solution, but it looks as if I'll have to get off my ar$e and move the sensor.

[rev-erend]

GreenV8S said:

I was hoping for an easy solution, but it looks as if I'll have to get off my ar$e and move the sensor.

Mount it in the boot..

[Boosted LS1]

^ Or in his ear

[rev-erend]

Or map it properly and do without..

http://www.thor-racing.co.uk/KNOCK_BLOCK_-LNK_KNKB...

[liner33]

I had real problems with my pulsing my nitrous solenoids due to the ecu picking this up as knock and recording high spikes of knock , took me a while to work out what was happening

Guess you are going to have to move them mate

[GreenV8S]

Today I've splashed out on a set of colder plugs and a GEMS style knock sensor that will go in the side of the block. Hopefully that will suffer less noise and my KnockSenseMS will be able to cope.

Although I'm aiming to map it to avoid knock, I can't completely rule out the danger. For example this current problem only began after my WI pump started playing up, and this is only one of many problems that could potentially push it into knock. So I want as many layers of protection as I can get, and the knock sensing will (if I ever get it working reliably) just one more line of defence to stop me blowing the engine up.

[stevieturbo]

rev-erend said:

Or map it properly and do without..

http://www.thor-racing.co.uk/KNOCK_BLOCK_-LNK_KNKB...

That isnt very good...in fact IMO, its quite poor and also picks up huge amounts of noise.

The plain audio side is ok, but the 0-5v datalogging side of things picks up far too much background noise, to be of any real use.


Phormula's latest KS-4 looks to be interesting.....and I'll be getting one soon.
http://www.phormula.co.uk/Default.aspx

[eliot]

GreenV8S said:

my KnockSenseMS will be able to cope.

So same as me then... did you see my reply above?

[GreenV8S]

eliot said:

GreenV8S said:

my KnockSenseMS will be able to cope.

So same as me then... did you see my reply above?

Yes I noticed it. I'm going to try the new sensor position and see if it works any better like that. As it is, it's useless. It comes on very obviously with throttle but I mapped out how much 'knock' I was getting over the load/rev map and it was triggering everywhere.