High Knock Reading

[Damo]

Faulty knock sensor's in GTR's is common apparently, croydon racing can confirm this.

139knock ouch! although you'll proberly find majority of the time its on in 1 or 2 specific load points, if it was getting that level through all the rev range thats bad bad new...

if it is only happening on 1 or 2 load points are u saying this is not much of a concern? How many degrees of timing would u expect to take out of these 1 or 2 cells to bring it back to safe levels?

[paulr33]

from my experiences with knocking

its likely to occur near 4500 thru to 6000 on full load.

on the r33 gtst its usually on load points 14 to 15 to 16 as this is the airflow max load area. it certainly is possible that a few cells in a row have their IGN timing too high in those cells, 3 cells with a value too high could certainly give the feeling of a faulty knock sensor or "all through the rev range".

if a knock sensor was faulty i would expect either no signal or a constant wrong signal, ie knock 56 always regardless or engine load and / or operation. you can use the apexi powerfc's temp IGN adjust to dial out 3deg across the IGN map, this usually naps out any knocking. then if that does sort it out (very likely) you need to find where on the map the bad cells are and out 3 deg for those (using map tracer)

IGN COR = Temporary Ignition Correction

INJ COR = Temporary Injection Correction

On your hand controller goto the main menu

SETTING (Press NEXT)

IGN INJ (Press NEXT)

You will be presented with

IGN COR INJ COR

press DOWN 3 times

and Adj for IGN Cor will change to -3

Press PREV

now using MONITOR - 1 CHANNEL - KNOCK

and then pressing DOWN to show max knock value you can see how that affects the tune and its knocking levels.

Note: The igntion correction is reset back to 0 on poweroff as its a temporary adjust mode only and not meant to be used every day.

[cameron]

if it is only happening on 1 or 2 load points are u saying this is not much of a concern? How many degrees of timing would u expect to take out of these 1 or 2 cells to bring it back to safe levels?

No its still not good for you'r engine but at least you know you havn't blown it up if its only 1 or 2 points. It should be taken back to you'r tuner to get fixed. At 139 knock as posted above -3 deg should do the trick.

Also further back in the post you guys were talking about knock level's and being able to hear it in the cabin. This aint always true, I've seen 70 knock on FC h/c and it was really loud inside the car engine was rb26 - this knocking was due to bad fuel car was sitting for couple mnth's.

But on a rb25 i've herd 80 knock (again FC H/C) through my chassis ear and no one else could hear it in the car or out side - car was on dyno. although this was at 2 points at high rpm...

So it can vary - who's know's why but its all bad new's !

For a stock engine i like to keep level's around 20, for somthing stronger, forged etc.. 30 - 40 is ok.

Their are many different reason that pre-ignition can occur:

* To hot of a heat range on you'r spark plugs

* Hot intake temps into engine

* To much ign advance

* Lean mixture's

[paulr33]

Here are some possible causes for each also;

* To hot of a heat range on you'r spark plugs

Wrong plugs, dead plugs, shagged plugs or close to failure

* Hot intake temps into engine

Poor cold air intake, pod sucking hot air in engine bay

Also too much boost, more boost can mean much more heat if out of effiency of the turbocharger's compressor wheel (compressor map will tell you)

* To much ign advance

Timing too far in one or more cells on the IGN map

* Lean mixture's

Fuel pump can't keep up or tune too lean

[benl1981]

Ive had mine tuned by a reputable tuner (Dyno dave..recommended by SK) and found I get spikes. I can not hear the knock and spoke to the tuner and he believes it is mechanical noise that isn't picked up as much if you richen the mixture - but then you get poor response and power.

Not always the case but I hink it isin mine. I'm taking it back for him to check, but he says he may turn down the sensitivity on the knock sensor - apparently you can do that via the FC datalogit software.

Edited May 7, 2006 by benl1981

[paulr33]

You can't adjust the knock sensor sensitivity. Dyno tune's do vary a little bit and its likely that once you throw it on the road and give it some real engine load that it knocks different on the dyno. Every R33 tune I've seen is perfect on dyno, drive around and it knocks in a few spots on the street.

It just a case of a few cells are too far advanced.

Take out 2 deg timing in those cells and all fixed.

[benl1981]

You sure? He reckons you can. Ill have to take it back and see what he finds.

I got it tuned back in January but haven't had a chance to organise a time with him as he is very hard to get to.

You can't adjust the knock sensor sensitivity. Dyno tune's do vary a little bit and its likely that once you throw it on the road and give it some real engine load that it knocks different on the dyno. Every R33 tune I've seen is perfect on dyno, drive around and it knocks in a few spots on the street.

It just a case of a few cells are too far advanced.

Take out 2 deg timing in those cells and all fixed.

Edited May 7, 2006 by benl1981

[paulr33]

I have datalogit in front of me and there is no where to change knock sensor sensitivity.

Apexi FC PRO is the same, can't change it or even view anything knock related

[benl1981]

Right. I'll go and alk to him when I get a chance.

It is a fairly crude way of measuring knock - little microphones that try to seperate other noise and determine what is knock, I think a lot of people have found knock over 80s to be unaudible, depending on the engine. Some engines have a lot of internal noise.

[cameron]

Yeah as far as i know datalogit doesn't have a settings that allow's you to change the sensitivity of the knock sensor's. You can change the rate the the light on the dash flash and at what level - default is 60.

[MattSR]

Paul, I think ben has confused knock sensor sensitivity (say the three times quick) and the knock threshold that triggers the check engine light...

[Fangz]

i think i have just landed a record 182 is what i got 2day, i think the timming is up 2 shit

im getting it tunned on wedensday so ill see how that goes

[paulr33]

ah yes, you can certainly adjust the flashing light sequence for picking up knock and at what level it should flash, certainly wont alter the reading. it wil just hide the true problem i suspect, ie: move the warning flash on dash to 150 knock instead of 60