S-afc2 knock detect

[RS12Turbo]

Don't know how normal or abnormal this is.........Ever since I did my swap, my s-afc2 will detect knock. The weird thing is it will display 0 for like a hr of constant hwy cruising, then all of a sudden it will start teetering between 0 and 1, then after a while will stay on 1.....it will keep doing this up till about 5. Other times it will stay on 0 while cruising, but then when I come to a stop and idle down, it will go to 1 or 2, then when I get back above 8% or 9% throttle, it will go to 0 again.Both scenarios start only after about a hour of driving. If I shut off the engine for 5-10 mins while getting gas or something, when I crank it back up, it reads 0 again for about another hour, then it starts again.Is this a common normal problem with the s-afc2, or do I possibly have an issue somewhere? If an issue, where should I start looking?Thanks for any info

[progman]

Hey,

Mine does the same exact thing. I get even higher numbers sometimes; up to around 15. This only happens when I'm driving for about 45 minutes or so. Sometimes if the car wants to stall for some reason like the clutch being let out when giving it no gas at a stop it will also do this.

[r34 gtr]

mine also does it when its hot. if it is very hot outside it will scream up to 20-30, but the car runs like a top. when im cruising it will slowly creep up to 6-8, regardless of how im driving. i think its a bunch of crap. screw the safcII.

[RS12Turbo]

Wheeeewwwww, I feel better now knowing I'm not the only one.Now could it be possible the knock sensor is going bad, and actually retarding the timing when the afc picks it up? I hear they crap out over time.......atleast on the vq30 Maxima's

[r34 gtr]

mine says there is less knock correction when i give it gas, which i thought would be the opposite. who knows. i would think it retards timing, as thats it job when it detects knock right? i havnt heard of these sensors going bad, but you could be right.

[float_6969]

The timing retard isn't a linear relation to the amount of knock it detects. It's more a breakpoint kind of thing.

Under a certain point, it doesn't matter how much it "hears" it leaves the timing alone.

Once it reaches that breakpoint, then it backs the timing off.

I would also think that they are effected by heat as well.

[Jiggyfry]

Ive wondered about this many times too. I have an Safc2 on my Ka and always have a knock reading anywhere from 0-25 counts. Engine runs like a champ though.

[Flybert]

When the SAFC2 is calibrated properly, it is normal for it to read knock after driving for a while. The hotter it is outside and the hotter the oil is, the more knock it will read. On really hot days sitting in traffic, I've seen it go up in the 30's before. If you give it gas the knock will go away. That is normal as well.

When you experience legitimate knock it will spike to 50+ so make sure it's in peakhold mode and go blasting around to see if the knock sensor picks up some real knock. Check the peakhold reading. I've seen knock of 100+ due to running high boost at the track on a hot day when my 91/100 octane mix got a little low and there was too much 91 in the tank.

The SAFC2 knock monitor is priceless to me at the track. It always lets me know when there's too much 91 in the tank. Nowadays I run pure 100 at the track so I don't check it very often.

The main thing is to check if there are spikes when on throttle and you see them by recording or by checking peakhold. Checking peakhold is the easiest thing to do.