OzGemini.com

:: Holden Gemini Forums
It is currently Sat Feb 29, 2020 1:14 pm



Post new topic Reply to topic  [ 12 posts ] 
Author Message
 Post subject: Fitment of Knock sensor ?
PostPosted: Sat Aug 08, 2009 5:12 pm 
Offline
Long Term Member
User avatar

Joined: Tue Jul 25, 2006 11:09 pm
Posts: 1597
Location: Brisbane:- 1.5bar above you
hi guys i know this is a subject that is brought up a lot

today i founnd my TPS has s*#t itself on my gemini so while i was searching for the variable resistor type instead of thw switch type i come across listings for knock sensors.

www.aca-auto.com.au
go to sensors catalogue

and i found 3 that mount onto the block just by ne bolt through the middle.

now my question is engines fitted with knock sensors is the block itself made in such a way that the ping characteristics travel towards the sensor.(eg. its internal casting)

i know if yu hit a vr v6 eng on the plenum with a hammer its enuff for the sensor to pickup and retard the timing yet the sensor itself is mounted on the lower drivers sde of block.

check the site out look up knock sensors you will see the three i mean.

2. in regards to my TPS i have a ford XF throttle body and want to change it too variable resistor type. should i get tps 011 or tps 012. same catalogue as knock sensors.

_________________
Thats Right Im a Long Term Member
WASTEGATES - WASTE 8S
IF YOU WANNA FLY, GIVE IT MORE P.S.I 8)


Top
 Profile  
 
 Post subject:
PostPosted: Sat Aug 08, 2009 6:36 pm 
Offline
Was dangerous_dave
User avatar

Joined: Mon May 30, 2005 12:38 am
Posts: 2033
Location: MEL
I think there are certain sweet spots on the engine that work well for picking up knock.

Also every engine / application would have different frequencies that represent knock, i think OEM's tune the filter for the sensor for each application.

I plan to have a crack at this soon, i have a knock sensor and an STM32 handheld eval kit to sample the sensor and display the data:

Image

I'm just going to copy a knock sensor analouge filter circuit off the net:

http://img216.imageshack.us/i/knockcircuit2fv2.jpg/

And do alot of driving, comparing "seat of the pants" feel with the readout from the sensor.

I was going to start with an inlet manifold stud and maybe try a few other spots to see if one is best for picking up knock.

_________________
Gemini: Light weight, low cost RWD automotive platform.


Top
 Profile  
 
 Post subject:
PostPosted: Sat Aug 08, 2009 7:38 pm 
Offline
Long Term Member
User avatar

Joined: Tue Jul 25, 2006 11:09 pm
Posts: 1597
Location: Brisbane:- 1.5bar above you
id be very interested in seeing your results this could be a huge step forward for diy tuners eg. me i have microtech so i could probly have it to activate to retard my timing under boost.

to help with the filter process i know you can get those engine microphone (you wear earphones) when on the dyno tuning to hear for pinging maybe while using this instrument it will help make the filter tuning part a lot quicker.

when you hear it in your ears you will be able to tune the filter.

I HAVE NO IDEA WHAT THE FILTER IS.
BUT IM HOPING YOU GET WHAT I MEAN

_________________
Thats Right Im a Long Term Member
WASTEGATES - WASTE 8S
IF YOU WANNA FLY, GIVE IT MORE P.S.I 8)


Top
 Profile  
 
 Post subject:
PostPosted: Sat Aug 08, 2009 8:38 pm 
Offline
Long Term Member
User avatar

Joined: Sun Jul 09, 2006 6:13 pm
Posts: 5903
Location: Albury/Wodonga
As per Dave's comments.

I have explored the knock sensors used on Delco systems and from all I have found out, each knock sensor is made to suit an individual engine type. Using it on a different engine is about as random as it can get. The chances of one being suitable at all are about lotto odds. The only way to figure it out is to set up specialised expensive microphone units at different parts of the block and run it on a dyno till you force it to ping and you will get the recorded info you need to start designing the correct knock sensor foe your engine. It's going to be an expensive project and by just trying to fit any old sensor you have the risk of it failing to read real knocks and allowing the engine to continue advancing even though it should have 'heard' it and analysed it as a knock.

_________________
.

I do not give permission for anyone to reproduce content from my posts.
Reposting any of my forum posts (or substantial parts thereof) breaches the copyright act.


Top
 Profile  
 
 Post subject:
PostPosted: Sat Aug 08, 2009 9:27 pm 
Offline
Long Term Member
User avatar

Joined: Tue Jul 25, 2006 11:09 pm
Posts: 1597
Location: Brisbane:- 1.5bar above you
still its possible to get some sort of reading from it (knock) once that knock is distingushed under a continual engine load (up a hill) you could then tune into the frequency to get a reading of that knock equivalent to load and engine speed while already knowing what the timing is set at you could then sense in a new timing curve into the ig map

_________________
Thats Right Im a Long Term Member
WASTEGATES - WASTE 8S
IF YOU WANNA FLY, GIVE IT MORE P.S.I 8)


Top
 Profile  
 
 Post subject:
PostPosted: Sat Aug 08, 2009 9:38 pm 
Offline
Long Term Member
User avatar

Joined: Sun Jul 09, 2006 6:13 pm
Posts: 5903
Location: Albury/Wodonga
I wouldn't trust in that sort of thinking. The knock sensor hears all sounds and the filter circuit sorts out the range of sounds and picks only what it knows is the sound of knock onset then sends a signal to the ECU. That's the costly part, designing a filter to suit the engine you are trying to protect and lets face it, why do you want a knock sensor? So you can run to the closest point possible before it detonates and the knock sensor job is to guard against that occurring but if it can't hear and pick out those exact sounds then it fails in it's job and you punch a hole through a piston. The other lesser concern is misreading so it assumes a knock when it's really hearing something normal or a noisy cam clearance. It's a huge job developing a filter to suit your special engine.

That's why I have excluded the use of a knock sensor, to me it's just pushing a tad too far expecting an unknown device to be accurate enough to protect my investment.

If you do manage to chat to wfc, he can probably tell you more about knock sensors than anyone else here, he did work as an engineer for the company that designs the Delco engine management systems.

_________________
.

I do not give permission for anyone to reproduce content from my posts.
Reposting any of my forum posts (or substantial parts thereof) breaches the copyright act.


Last edited by Germinator on Sat Aug 08, 2009 9:40 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject:
PostPosted: Sat Aug 08, 2009 9:39 pm 
Offline
Regular
User avatar

Joined: Tue Jan 20, 2009 8:12 am
Posts: 329
Location: Brisbane (sth side)
7URG3M wrote:
still its possible to get some sort of reading from it (knock) once that knock is distingushed under a continual engine load (up a hill) you could then tune into the frequency to get a reading of that knock equivalent to load and engine speed while already knowing what the timing is set at you could then sense in a new timing curve into the ig map


x2

Yes each knock sensor is designed for a particular engine but the sensor itself is still going to pick up the knock... you just need to alter how the signal is interpreted by your system and how it acts on those readings.

_________________
Cheap repairs and sprayjobs, nothing is too big or small-PM for details!


Top
 Profile  
 
 Post subject:
PostPosted: Sat Aug 08, 2009 9:41 pm 
Offline
Long Term Member
User avatar

Joined: Sun Jul 09, 2006 6:13 pm
Posts: 5903
Location: Albury/Wodonga
The ECU just reads an on or off signal from the knock sensor filter. The ECU can't determine knock, the filter does that. The issue is designing an accurate filter.

_________________
.

I do not give permission for anyone to reproduce content from my posts.
Reposting any of my forum posts (or substantial parts thereof) breaches the copyright act.


Top
 Profile  
 
 Post subject:
PostPosted: Tue Aug 11, 2009 9:03 pm 
It is possible "once that knock is distinguished under a continual engine load... ", but repeating what has been said above, it is determining its uniqueness.
That means frequencies-cum-waveshape.
And that varies with each engine (though similar 4 cyls may be similar) and block type and where in the block.
IE - a knock sensor for a particular engine is a tuned microphone (or a mic with a filter in later electronics) that is fixed to the block appropriately (ie, equidistant signals etc).

And it's probably much easier isolating the "knock" signal than removing the others (bearings, slop, ignition, valve-seating) (obviously?).

To add knock sensing to an un-knock-sensed engine, I would use splug ionic sensing since AFAIK knock is a characteristic waveform and should be more recognisable between engine configurations.
Not that I know how signal processing has progressed over the years, but I'm sure it has come a long way since my involvement with Motorola 56000 DSPs over 20 years ago.

If devising an old skool knocker, I'd get any microphone that handles the environment - probably piezo type, maybe earbud speakers etc - and a variable bandpass filter or even a plain audio graphic equalized and test for knocking & non-knocking sounds. I'd probably then build a specialised circuit and consider one per pot.
The filters are usually no higher than 6kHz with 4kHz being typical. They have to be gated (timed) to only read the signal for whatever degrees after ignition.


Top
  
 
 Post subject:
PostPosted: Tue Aug 11, 2009 9:32 pm 
Offline
Long Term Member
User avatar

Joined: Sun Jul 09, 2006 6:13 pm
Posts: 5903
Location: Albury/Wodonga
...and as much as a Gemini engine has it's own unique exhaust sound that distinguishes it from other cars, so do the knock sensors. Think of it this way... an EH Holden with a 179 has a distinct sound and it is different to the sound of an HK with a 179 for instance even though each uses the same basic 179 engine and three speed crash gearbox. What then makes it sound different? It can only be the combination of things that are different like the exhaust system, the wheel diameter and diff ratio.... small individual things buy collectively a trained ear can pick the car model without even seeing it, just by sound alone. funny thing is a knock sensor is similar. Don;t assume any other 4 cylinder engine is going to produce similar knock sounds to the knock sensor. The engine may have a similar bore and stroke, (I'd be experimenting with a knock sensor off an engine with the same bore and stroke) and with the sensor mounted in the same location. Things that WILL change the sounds the filter is set to null out are created by the shape of the combustion chamber, the valve locations, the spark plug locations, the piston head design etc... lots of variables indeed.

Experiment by all means but I wouldn't trust my experiments to save an engine that is intentionally tuned to knock so the knock sensor circuit swings into action protecting it from damage.

_________________
.

I do not give permission for anyone to reproduce content from my posts.
Reposting any of my forum posts (or substantial parts thereof) breaches the copyright act.


Top
 Profile  
 
 Post subject:
PostPosted: Wed Aug 12, 2009 8:18 am 
Offline
Long Term Member
User avatar

Joined: Tue Jul 25, 2006 11:09 pm
Posts: 1597
Location: Brisbane:- 1.5bar above you
all i meant in my post was so that you could get an idea of the frquency needed to tune int detecting like i said before im not a full tech guru but dyno tuning hasnt changed much from the days of road tuning when you or your fathers were doing it.

back then and still is its done by seat of the pants and by ear.
i tune my vk commodore twice a week by ear monday mornings fill it up with E10 pull the timing back a little stab it out of the servo no ping till im right up there. come fri arvo fill up with BP ultimate advance it before i leave and do the same thing again if i feel ive gon too far i will pull it back a lil.

all im wanting to know is if the knock circuit can be made up instead of it actually retarding the timing you could use it as a tuning tool if its sensing make it activate a ight or buzzer then you know at that load and rev the timing needs to be retarded a lil there.

end rant ^-- sorry for long post
ill be honest ive never heard my gemini ping but i can definately hear my vk ping (by ear) now weather that has something to do with the OHC gem motor im not sure.

_________________
Thats Right Im a Long Term Member
WASTEGATES - WASTE 8S
IF YOU WANNA FLY, GIVE IT MORE P.S.I 8)


Top
 Profile  
 
 Post subject: Re: Fitment of Knock sensor ?
PostPosted: Sun Dec 29, 2019 8:38 pm 
Offline
A Nice Guy

Joined: Tue Feb 03, 2009 5:39 pm
Posts: 105
Location: Lismore
For anyone that finds this on the googles
Ignore the above, its conjecture.

Hp academy and others have proven you can mount a knock sensor anywhere and the only change is the amount of noise to be filtered, the knock signal remains

Buy a plex or a knockbox or a knock monitor pro(my choice) and dial in your efi tunes with literally any old GM style knock sensor.

Churrrr.

_________________
TD. daily.
TE 2dr
Kevin wills 6/7/08

I Don't Like Hills...


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron