To be honest I would think that the knocklink shows frequencies 'around' the 6400Hz mark. So the LED's would be steps up to the red which would be at the point of positive DET at 6400Hz?

Stu

 

Ok just for the people who admit they know very little on this subject...be careful what/who you listen to when it comes to your engine just in reading through this thread briefly its obvious that pretty much everyone who has posted knows very little about the subject, lots of second-hand 'knowledge' on here, read with caution

 

The led's are the volume. the more that light up the more the noise or knock is.
From the testing i've done it does look like the frequence that it targets seems to be more around that 6-6.4khz which isn't the best for bigger bore engines like the ej257(but does still work well).
I've seen and herd good knock at 5700hz on a spectrograph when the knocklink saw nothing.

 

Daniel -s your post made me pmsl!...Excellent!

 

Then share with us your wisdom of the mysterious KL oh wise one.

 

The knocklink is effectively a peak hold VU meter with a bandpass filter of slope 6dB/oct.

Unless the exhaust is very noisy or you are at high revs, I can usually hear moderate detonation in the cabin, but I learned from listening to det cans whilst watching a knocklink.

Unless you have aftermarket forged pistons I would leave the knocklink on maximum sensitivity and any spike should be investigated/corrected. It is possible even at 200 BHP/litre that you might never see more than 2 green lights and even that at over 6000 RPM on a quiet engine.

 

Aim to please and all that

 

Lol, dont ask me although i work in engine calibration and effectively map engines on a day-today basis i only share my immense wisdom of power rangers and my little pony on these forums....i'll leave the rest to you guys.

All i'm saying is be careful...i'd hate to see someone blow up thier pride and joy after taking advise off forum-muppets that are clearly out of thier depth.

 

Which posts should I trust on this thread as I know very little on the subject matter.

TIA

 

p1marks's are sound

 

This is exactly my point!People come on here ask a simple question get all this ****.And then don't know who or what to trust,bleeding joke IMHO

P1Mark knows what he's on about

 

Ignore [Davey] and Trems and otherwise this thread is fairly sound. The contributions from [Davey] are simply misguided and the ones from Trems are "look how much I know and I'm not telling you".

 

When it comes to things like this your best bet is to get in contact with either the manufacturers of the kit or a respected tuner, there are a few who post on the forums who specialise in subaru tuning such as andy f, best send a polite pm to someone like him, always take really techy advice from the experts, not forum 'enthusiasts' not trying to **** anyone off but surely you guys admit there is alot of crap spoken on forums, i dont normally say anything but when its something in my field and i see obvious bad advice then its hard not too....just my 2p.

 

CockLinks are one of my pet hates, why? Because it does NOTHING that the Subaru Knock Sensor doesn't do and the Subaru ECU reacts a lot faster than any owner on here could do to knock!

Adjusting it until it doesn't show RED anymore is just an example of the uselessness of the item!

Now, the 'hobbyists' on here who 'play' with cars think they give them some info thats useful - so fair enough.

It also looks good to your chavvie mates.

Therefore it has a purpose - it makes you 'think' you are in some form of control or makes you the kingpin outside Maccies on a Friday night .... as a serious driving tool it's utter crap (or Subaru would fit one as standard!).

I drive and can hear det. I can hear knock - I am a proper old school driver who laughs at Rally Wannabbeees and their CockLinks

Thats my opinion - it is shared by MANY, MANY more - up to you .......

Pete

 

haha, i like this guy

 

Thanks Stu

It all makes sense now (though you have to laugh at the description of the Northstar engine as being a 'high performance engine' because it produces 1 hp per cubic inch , they may make 300bhp, but from 4.6 ltrs FFS)

 

Can you tell me why I'm missguided?

Lets look at this a different way:

So if I went out and bought a little device that flashes up a light telling me my oil pressure is dangerously low; It can be "calibrated" to the car it is installed into, so I install it and the light is on so I callibrate it so the light goes out.. It later turns out my engine was holding 12psi at idle and the crank throws a shell..

Wow that would be a useful device

In the real world I would use an accurate method of measuring the pressure before I set the device up.

 

megrac and p1mark have already corrected you. You made flawed assumptions and spouted incorrect knowledge and didn't follow it through with a cohesive argument when you were corrected.

As has probably already been stated, you would also find that people do not simply reduce the sensitivity until they stop lighting up - they either use det cans to calibrate or more likely leave it on maximum which we know for mounting the supplied Bosch sensor near the factory one should not give sudden red spikes on a factory engine.

If you want me to comment on the tolerances of the components in the knocklink and why it does not require calibration, or you want me to detail the knock control mechanism of the standard ECU and why on a GC8 it doesn't respond to knock at all engine loads and RPMs especially when tuned then I could do that, but at present I have better things to do.

 

hang on a minute guys i am getting pretty confused here.

p1mark, you said
where as Graz said

The KnockLink monitors detonation (fuel air mix exploding before the spark is fired). If it is occuring it puts tremendous strain on the engine as the combustion occurs before the piston reaches the top of its stroke, therefore pushing down on a piston that is still moving up. This can cause big end failure. The increased combustion temperatures and pressure caused by det can also melt pistons or blow holes in them.

what is going on what is the real deal?
sorry, not trying to be a nuisance, just trying to learn

 

Graz made an error.

 

Reading the article about det & pre-ign, all damage is apparently focused on the piston (& bore).
So does it follow that Scoob big end damage isn't related to det but more to do with oil pump failures or possibly a poor oil change?

Is the frequency picked up by the KL a very specific resonance only made by det, or is it one that can come from various engine/transmission problems?

NIck

 

If the CockLink worked then Subaru would fit them and link them to the ECU rather than having Chavvie flashing lights.

But then, the Chavs, Hobbyists and Rally Wannabbees would STILL want some lights!!

Pete

 

If you blow up a Subaru gearbox it lights up a knocklink Nick, so yes other things can make a noise. If you see I mentioned above, the filter is 6 dB/octave. If you read up on filters you will see this is shallow. An octave is a doubling or halving of frequency and 6dB is the equivalent to moving double the distance away from a source of sound. Make sense?

 

If Subaru pushed the boat out and made 2 l cars running 350 bhp+ then the knock (det) control process would no doubt be reviewed (as with all other ECU control systems) and would throw the "chav" CEL on/ go into limp mode in event of bad det events.

For std cars then yes, a KL is probably pointless unless it also serves to pick up noise from other problems - hence my question about what other potential failures will resonate at 6.5 kH.

Nick

 

i would be interested in peoples opinions of this (those with experience and who are not on a wind up or an idiot - Lewis/Davey/Trems etc)

Undoubtedly oil/temp related big end failures (without any det in the combustion chamber) are common.

My own Subaru did this. high speed, 115 deg oil, no KL activity and no sign of det anywhere when i stripped it.

Im more interested to find out if det can kill big ends or mains. the common concensus is the shocks down the rods can either minimise the oil film so much that failure may happen, or actually bruise the bearing surface? Has this been proven?

I have a fair amount of experience in tuning/building N/A bike engines for racing with very high specific outputs. These are set up very much on the edge and top end damage from det is not uncommon if things are not spot on.

All the blown engines with big end failures i have rebuilt (maybe 15 or so) - none have shown any sign of detonation in the chamber. conversely all the engines i have built with piston damage due to det have never shown any bearing damage.

 

Maybe they will WRC graphics and neons as standard too? And one of those stupid f**king scooby doo teddys? And what about throwing in a Subaru Cap and Jacket so you can look an even bigger plum

 

Bye Bye [Davey]

 

I quoted the wrong post there by the way

 

Hear a noise anyone?

 

detonation has nothing to do with big end failure, lack of lubrication is what kills bearings, or just old age...even properly lubricated engines will wear with use, obviously the harder the car is used the quicker they will wear and therefore fail.

Det causes huge localised heating of the combustion chamber, and even with forged pistons fitted the piston crown is the weakest link and will undoubtedly melt, similar engines i.e those with the same intake design (i.e head ports piston crown design) and spark plug position will fail in the same place.