knock sensors...

[Justin_Inc]

01 2.4L auto cavalier

when i'm browsing around in the VCM Editor under engine/sparkcontrol/knock sensors nothing shows up so i'm taking theres no support for this yet. Is there any way to turn down the sensitivity of the knock sensor? I'm seeing 6* steady or knock retards, running 94 Octane Mohawk (ethonal blended) gas. I know this is phantom knock (been through all of the steps to get it reduced) i see this right from idle when i step on it all the way through the RPM range. (even in P/N with no load)

engine was a stock rebuild on a new block and the knock sensor was re-located from the back of the block to the head above the transmission (hence another reason why i know its phantom) this was due to it being an older block so the newer style (2wire) knock sensor wouldnt fit in the stock location.

so any input or am i going to totally kill this knock sensor and the CELL that goes with it in hpt and just run a guage off of the single wire sending unit in the stock location?

thanks

[Shifted]

You can reduce the Knock Attack vs RPM table, I set mine to a max of .500. Its on the spark retard screen.

[c24s/c]

what is knock attacK?can you explain it further, please.

Thanks!

Nate

[Shifted]

Knock attack is the amount of ignition retard for each knock "event". This is how agressively the ECU retards the timing when it gets feedback from the knock sensor.

[c24s/c]

ok. who is that different then when the pcm jumps to the Low octane timing table (with more retard). What do you mean by 'event'.

Nate

[Justin_Inc]

thanks shifted!

I turned it down about 1/2, i'm going to have to do something with the location, its picking up too much cam/combustion/transmission noise where it is.

[Shifted]

ok. who is that different then when the pcm jumps to the Low octane timing table (with more retard). What do you mean by 'event'.

Nate

The ECU doesn't "jump" to the low octane table, it learns towards it. So in the event it sees knock, it reduceds timing towards the low octane table, so it is interpolated somewhere between the two. By event, I mean a voltage feedback large enough for the ECU to determine that as a knock event.

[c24s/c]

thanks shifted. I was reading up on it, and that makes sense. Hence y the knock attack, you tune it down, so it doesnt retard the timing so much.

But one other thing that comes to mind. Since it reads voltage, whats the voltage range of the sensor? my display shows a max of 10. I'm looking at knock attack and it can be triggered by coolant temp, barometric and rpm. Now if i'm sitting in line at the track, or in traffic, i know my temps go up. Personally i dont care if they do, cause ill never let it overheat. But my point is, the coolant would trigger it before barometric or rpm. So wouldn't it be a benefit to almost delete that one, and have KA come on vs rpm. Weird tho, looking at the knock Attack vs baro, and it only goes to 105kpa, not into atmospheric. Isn't that kind of pointless on a 2bar map setup?

[c24s/c]

just compared the na vs sc file and all the knock attach is the same.

weird no?

[Shifted]

Its your call really, they are just multiplier values. As far as not going into atmospheric, it really doesn't matter, you see that the attack rate values are all 1.0 after like 50kpa, so it just uses the last value it finds in the table after 105kpa, so in essense, it is 1.0 for all values over 105kpa.

GM does wierd things with thier files, so try not to think of that as good practice

[c24s/c]

So it takes the stock 1.00 after 105kpa, most likely i'd already be under full boost at 3-4rpm so my knock attack would be full on. So really modifiying the rpm table will control anything from 105-210 (full range of 2bar map sensor). Although with 8-10psi(173.95kpa) will be my max.

ok. I think i'm getting the hang of this.

But what overides what? If i lowered the rpm knock attack values below the bara values. Ie. 1.00 baro multiplier and .500 in rpm, would current rpm condition be used and overide the 105+kpa condition?
IE.. 5000prm what would the KA multiplier be? .5 or 1.00.

Nate