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Another Knock Thread. Urgent Explonation Please

WogsRus

By WogsRus,
in Engines & Forced Induction

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WogsRus Veteran

WogsRus

Posted
Posted

Ok so all those with an SAFC II, know that the knock sensor needs to be calibrated.

So first you let the car warm up and set the knock at 1500rpm and then at 3500rpm. This sets the basline of the knock sesnor.

IE as per this post:

http://www.skylinesaustralia.com/forums/in...=132717&hl=

Ok so with the new ECU i have not reset the knock on the SAFC II so i could compear this to the new ECU to make sure it wasn't doing damage.

So with the new ECU, the knock values are exactly the same as before, well in the same range, zero most days when cold and creeps up to 10-15 on hot days and stayes there.

However i have an interesting question.

If you go to SENSOR CHECK screen, you can see the raw value of the knock sensor, now at idle with no load, my car showed 0065, not sure what the units are, at 6900rpm, the value was 0125, so that is double.

However, back in the MONITOR SCREEN, the value goes from 0, coresponding to 0065, and then to 10, corresponding to 0125.

SO WHAT THE HELL, i do not understand the Knock part of the SAFC II, if the car was actually knocking, it would be dead, long time ago, trust me. There is no audiable knock, it is not lean and timming is at 18 deg, as at 15 it seams slugish, so bumped it up one by one, and 18 seams great.

The Figures between the old ECU, stock nissan one, and the new ECU, Central20, are the same, but i do not understande how the vlues relate to eachother.

in the SENSOR CHECK screen, is the knock value in volts, milivolts, what.

HELP i am going insane.

PS. The car has new pump, FMIC and all supporting mods, including exhaust, no cat, new plugs, splitfire coils ect. ect. Compression is near enough tto 150psi across all cylinders, and plugs looked ok.

Strik3r Experienced

Strik3r

Posted
Posted

that raw sensor monitor is the 'volume' being heard by the knock sensors.. knock is only determined to have occured when the volume breaches a certain level ^_^ so basically, your sweet ;)

someone with more knowledge and exp better confirm this, but i definately seem to remember reading that.

WogsRus Veteran

WogsRus

Posted
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I C, well i'm gona do a map trace to make sure it is all good, but so far i think it is ok. I can't hear any knock at all, and pinging, well that is a bit hard to tell, so hopefully i won't blow the engine. LOL.

Strik3r Experienced

Strik3r

Posted
Posted

yup.. always better to be safe than sorry..

remember that the knock sensor is just a microphone. Depnding on the mods your engine has, the engine sound will be different. So when you first calibrate your SAFC, you set the base 'knock value (basically, ambient noise) at 1500 and 3500 i think it was. this tells the SAFC what normal values are for your car. If the raw sensor value jumps by (as someone suggested in that other thread) 50 or 60 from base, then your probably getting some knock.

WogsRus Veteran

WogsRus

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opps today on a hot day on peak recall i saw 52 knock max and 10 idle so i guess that is about 42 total. Still all good.

Got it booked into the tuner to do a run and hopefully, fingers crossed it will be all good.

Busky2k Veteran

Busky2k

Posted
Posted

Forget about the idle readings. And its a perculiarity that the SAFC shows more knock on idle when the weather is hotter too.

Its the max value from a peak recall after a hard run that matters. If its 60+ then its real knock. I've mucked around with an SAFC II for 2 years and thats what i found.

WogsRus Veteran

WogsRus

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Cool, so as long as the differance between the idle and peak recal is 60, then it's all good?

Hay Busky2k, can you PM me with some more details explaining how it all works, the knock issue on SAFC II. Down here in tas there is no one to tune it properly, so i have to kind of so it myself and then check it.

So basically all i hve to worry about is the diferance between the idle monitor setting and the peak recal? Correct, as long as differance is less then 60 then all good.

R33silverS2 Mentor

R33silverS2

Posted
Posted
Forget about the idle readings. And its a perculiarity that the SAFC shows more knock on idle when the weather is hotter too.

Its the max value from a peak recall after a hard run that matters. If its 60+ then its real knock. I've mucked around with an SAFC II for 2 years and thats what i found.

Is this in monitor mode or sensor check in ETC? in sensor check at idle mine is like 0036 or something from memory, in monitor i have only seen 0.

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