Knock sensors

[milkandoj]

i want to replace my knock sensor even though it appears to work fine.

As ive swapped in the later model 808 ecu in my car, which ive read has better knock control.
Do they use the same part number knock sensor as an 87 jap spec manual car?
Mine being the first of the vr4s and the monte carlo's being the later ones?

If the 808 ecu reads a more precise or slightly different knock sensor knock sensor id rather them be on the same page.

Where are people buying the new ones from. Mitsi quoted me 200. Someone on here said they got one for 130.



Also, i run a stock 1 wire 02 sensor. To run a 4 wire even with the new ecu id say ive have to wire in a power source ect and cant be bothered. Or is it an easy swap where i could just splice in the wired to the harness?

Mitsi dont have them so ill probably go a bosch one though work. Any better brand to go?

 

[GVR40]

knock sensor is essentially just a microphone for the motor, and they are all the same

 

[Legume]

A little off topic but still related...
But does anyone know what the equation is that Mitsubishi uses to calculate the knocksum value?

Im not meaning the part where for example 3 knocksums over 7 makes it retard as seen on the logged data
What Im looking for is what perimeters are multiplied by what (and how much by) to give the knock sum of 7.

Ive stumbled onto it once but never come across it again no matter how hard I look.

 

[MDK87]

A little off topic but still related...
But does anyone know what the equation is that Mitsubishi uses to calculate the knocksum value?

Im not meaning the part where for example 3 knocksums over 7 makes it retard as seen on the logged data
What Im looking for is what perimeters are multiplied by what (and how much by) to give the knock sum of 7.

Ive stumbled onto it once but never come across it again no matter how hard I look.

wtf.....? :huh:
Lol, that flew over my head man, but good luck hey.

That's the first I've heard of different versions of knock sensor Gerard.

http://www.extremepsi.com/store/customer/product.php?productid=17887&cat=1060&page=1

I'm getting some stuff from them soon if you want me to chuck your sensor in the order as well mate.

I think there is also a guy on ebay who sells genuine knock sensors under the name of "Ongreen performance".

I have a prefacelift VR4 with single wire O2 sensor as well and need to change it. I'm gonna get a 4 wire one due to their price.

Just run one heater wire to an acc. triggered, fused 12V line, and the other heater wire to ground.

I believe the difference between the single and dual wire ones is that the single used the chassis/engine as the ground path and the dual one didn't.
Anyone care to correct/confirm this?

In this case, one of the signal wires can go to GND (checking polarity with DMM) and the other to the single wire that goes to the ECU.
If you already have 808 ECU you might as well just run another shielded wire to the ECU for the GND to keep stray noise out.

Ideas/yes/no?

Cheers

 

[DOUGMO]

the only thing with knock sensors is that they are tuned to "standard engines"

as soon as you modify the engine it changes the "note" of the engine which means the knock sensor is looking for a "note" that has now changed.
which can mean it reads phantom knock or it wont read pinging at all.

 

[MDK87]

the only thing with knock sensors is that they are tuned to "standard engines"

as soon as you modify the engine it changes the "note" of the engine which means the knock sensor is looking for a "note" that has now changed.
which can mean it reads phantom knock or it wont read pinging at all.

Oh really? I didn't think of it that way...
I'm not sure how though because your engine shouldn't be detonating even if you've modifying (well it's not supposed to! haha).

What is the best way to combat this problem?

 

[DOUGMO]

if the engine isn't detonating(which as you said it shouldn't) why have a knock sensor at all?

the best way to combat it is to leave the engine stock:thumbsup:

its a tough one mate but i dont even run one on my car- I just have a good tune:thumbsup:

 

[MDK87]

Well the engine shouldn't be detonating, but there's every chance it could even if the tune was good couldn't it? For example if something fails, or you turn a corner with low fuel, hot day+high boost etc??

Are you running a Mitsubishi EMS dougmo? Tim and I were discussing whether or not you can run without knock sensor and found out that if it is disconnected, the EMS will assume that the engine is knocking at 7 counts. How did you get around this? Or have you got and aftermarket EMS?

I'm just really paranoid about knocking now after one of my engine blew the HG because of it.

And +1 to that! Stock 4G's are strong!

 

[DOUGMO]

i am running an autronic stand alone ecu mate

 

[bazeng]

What DOUGMO is saying is very true.

Knock sensors are tuned from the factory to suit a factory vehicle.
Once you change your exhaust / cams / pistons etc the frequency of the knock will change. Your knock sensor will not be working 100%.

Motec and Autronic have recently (within the year) released its knock sensors and they both were based on recordings of knock using a mic and identifying the freq of which knock occurs.
Then if the ECU see's that freq, it will regard it as knock and pull timing.

Now, Motecs I believe are fully definable. So you attach the knock sensor to the vehicle (which is really a noise detector), run in on the DYNO, you have to make the car detonate, find the freq of which the detonation occurs, tell the ECU that this is the freq that you have to look for to pull timing.

Autronics are non definable. Richard (Autronic owner) has done the above and made it a fixed freq. That is why his knock detection systems are engine specific.

Full race cars do not use KNOCK sensors. With all the noise that race car engines make, the knock sensor would be pulling timing all day!

Knock control, perfect for the street car / occasional race / drag, but not really practical on a race engine. But that isn't saying that there are race cars out there w/o knock control.

 

[brisvr4]

Interesting read Barry. What I have noticed on various tech boards is the view that cyl diameter is actually the main thing that causes knock frequency. I.E the amount of time taken for the shockwave to move across the bore. Good for me as mine still has stock sized pistons. I really think that Mitsubishi would not be silly enough not to build in some sort of a larger spectrum that it senses knock at. I would think that this is where 'phantom' knock originates from.
It may not be the perfect system but I'd rather have that then nothing at all

 

[MDK87]

Cool, that was informative.
You're so smart Baz, you have answers for everything!

Is there a way you could perhaps "tune" the stock knock sensor in this way?
I have a friend with a 300ZX who says that it's a common fault that their knock sensors fail and retard timing heaps. He stuck a resistor inline to drop the voltage that is sent to the ECU.
Maybe we could do the same and stick a pot on it to "tune" it to drop only enough voltage to reduce phantom knock and other noisy things that aren't real knock?

 

[milkandoj]

Cool, that was informative.
You're so smart Baz, you have answers for everything!

Is there a way you could perhaps "tune" the stock knock sensor in this way?
I have a friend with a 300ZX who says that it's a common fault that their knock sensors fail and retard timing heaps. He stuck a resistor inline to drop the voltage that is sent to the ECU.
Maybe we could do the same and stick a pot on it to "tune" it to drop only enough voltage to reduce phantom knock and other noisy things that aren't real knock?

That seems a bit on the dodgy side!

If you modifying the motor and the frequency does indeed change... How do you know that the resistor is changing the frequency to the right one for your particular motor. What works for one bloke wont work for you if the stock sensor doesnt.
You would have to make the motor knock the watch the logs as see if it retards the timing. And try it with different value resisters.
Pretty inaccurate and dangerous.

I wouldn't bother I'm just going to replace the stock knock sensor.
I just want to make sure i get the sensor that came out on the monte carlo versions to match the 808 ecu i have put in my car.
As my early jap spec runs a different part number (when looked up via the vin number) than the aus spec one.
So id rather run the later version and the one that the ecu is tuned to listen to.

 

[MDK87]

Well yeah that's what I said to him when he told me about it lol, kinda dodgy!
But I was just wondering what baz thought of it just for shits and giggles.
I guess the resistor won't do much at all if the ECU "listens" for certain frequencies, because a resistor is passive and will only change the amplitude.
As for chopping and changing resistors, that's what the pot is for.

Yeah just get a stock one dude, if you're really worried, I have a knock sensor that (appears) to be in good condition which came from an RS, but tbh I don't think there is a difference, as no-one has said anything in regards to your original question.

 

[MDK87]

If it were frequencies that the ECU was looking for, once determining the bandwidth at which real knock occurs, could you use a pass band filter to eliminate noise given from the knock sensor that falls outside of theses bounds?

 

[bazeng]

Basically every car will need to be knock tuned individually.

I am assuming on a manufactures point of view, same parts, same frequencies therefor knock sensor will work well.

Now, to ideally tune / test if your knock sensor is working accurately, you would need a set of knock ears (basically a set of headphones that you wear while you drive / tune which has a mic attached to the block/head). I've put one of these on and if you are not tuning cars day in, day out, it is very hard to know what knock sounds like. This I guess is what gives experienced tuners that extra edge. Anyway, to tune you would have to use the knock ears and your knock sensor log and make sure that they see the same thing. You can also use a knock link module which is basically a pair of knock ears but displays LED warnings instead. They too can be adjusted.

I was thinking you could use a knock link module, wire in the red led (KNOCKING) to an input of an ECU to tell it that it is knocking. Now this would be applicable to ecu that has available inputs. You would have to tune the knock link with a set of knock ears first.

Anyway, you guys get the point!.

Apart from that, there are aftermarket modules that connect inbetween your ignition system and the ecu with its own knock sensor, which if knock is picked up, it retards timing by intercepting the trigger from the the ecu and delaying it.

Knock sensors is one of those things that cannot be 100% guaranteed.
But like Tim said, better than nothing!!

Here is an extract from the AUTRONIC KNOCK MODULE MANUAL (it shows how much risk there is involved in tuning for/with knock):

1.0 GENERAL WARNINGS
If your engine type is unable to withstand knock, or you are unwilling to subject your engine to knock, or you are not experienced with detection of engine knock, or do not have instruments for the detection of knock, or do not have a good understanding of AUTRONIC SM4 ECU operation and ECU set up software you SHOULD NOT install this product. You should seek help from an experienced AUTRONIC installer.

These engine specific modules MUST only be applied for use with the intended engine types as listed on the product labeling. Also these modules are designed to use ONLY the OEMvibration sensor/s mounted in the OEM position/s. Failure to observe these restrictions will result in unreliable knock detection and/or
inoperative fail safe protection leading to serious engine damage or destruction.
This manual should be thoroughly read and clearly understood before installation is commenced.


Another cool extract:

NOTE 1:- FALSE KNOCK
These modules have been exhaustively tested in their intended applications and found to be highly resistant to the false reporting of knock when no knock is present. False knock detection will unnecessarily retard ignition
timing resulting in needless engine power reduction. False knock may also result in the ECU reporting a Knock Control Error (code 32) when the protective measures applied to control real knock fail to have any significant
effect on the reduction of false knock. In most instances false knock reporting can be attributed to a mechanical problem. The likely causes include
erroneous engine noise resulting from excessive valve lash, bent valves, sticking valves, worn or damaged camshaft, insufficient piston to valve, piston to cylinder head or piston to crankshaft counter weight clearance,
excessive piston to bore clearance or excessive crankshaft bearing clearance.


The manual also confirms that to test that the knock module is working, you advance your ignition by 5 degrees and make it knock to see if it pulls the timing. Now to confirm this, you will need knock ears. I'm thinking, has anybody tried wearing a set of knock ears and using it with a stock ecu?? See if you can actually hear it knocking when the ecu detects it....

I don't think a set of knock ears is that expensive..

 

[trq-str]

Not cheap. Good for a tuner tho

http://cgi.ebay.com/ebaymotors/Halt...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

 

[DOUGMO]

even changing to a stainless steel exhaust or fabricated inlet manifold can change the frequency of the engine, changing the efficiency of the knock sensor

 

[nate108]

i have a brand new sensor, in its box never used.
same as mentioned above

http://www.extremepsi.com/store/cust...at=1060&page=1

u can have it for $90 inc postage as im not fitting it anymore

pm me if u want it

cheers

nate

 

[milkandoj]

pm sent