Diablosport Forums

just wondering.. i have logged about 1.5 - 2 degrees of knock at WOT, ST and LT with the data logging feature.. is this enough to worry about and how do i correct if i need to?

anyone???

I wouldn't worry too much about 1-2 degrees. You can try removing 1* of timing in the RPM range(s) where you're seeing knock to see if that helps at all. If it's happening right at the shift, it might be false knock and you can ignore it.

1-2 degrees is fine in ST but seeing anything in LT is no good. Is this in an SRT8??

The engine is going to register some knock due to mechanical noise etc... and the knock sensors tend to be somewhat sensistive on those engines. mnunes is correct that if it's happening while shifting it probably is false knock.

this is the RT

From what I have seen, anything under 3 deg of ST knock is normal, specially at peak torque, 4k-5k. You do not want to see LT knock at all.
I would rather try to add a little bit of fuel than removing spark to reduce your kr even further if you feel up to it.

actually johan i didnt log LT knock, sorry i misread the log, i logged ST knock and Fuel knock... is 2* of Fuel knock bad??

Nah anything under 3 is acceptable, and yeah if you see LT knock yey got issues, but log the ST and ensure it is under 3.

cool thanx for the feedback.. the most i logged was 2.5* .. i adjusted the wot fuel and got her to 0*

what do you do if you have LT? Sorry, I'm new to this site.

brandondill wrote:what do you do if you have LT? Sorry, I'm new to this site.

More fuel and/or less timing advance.

thanks Quick.

Maybe Johan could give us a brief explanation of how the PCM arrives at long term knock retard?

My understanding of short term knock retard is this:
The knock sensors are tuned to the acoustic/vibration properties of knock and produce a voltage proportional to the magnitude of knock detected.
When knock is detected the PCM will pull x degrees of timing depending on how far over some threshold the voltage from the sensor is.
After some period of time (milliseconds) the PCM will check if the sensor voltage has dropped. If so, it adds back some timing.
This polling and restoring timing would continue until the knock retard has been reduced to zero.
The result is that a single knock event will result in a response that is gradually tapered off.

My assumption is that if, on some number of cycles, the PCM reduces the knock retard (adds back some timing) and on the next check the voltage has not dropped, it will move the knock retard to Long Term. I'm also assuming that Long Term knock retard is similar to short term knock retard but maybe a longer polling cycle. Short term knock retard is driven by the knock sensors. Long term knock retard is driven by short term knock retard. Short term knock retard and long term knock retard are additive. So if you have 2* of long term knock retard and 3* of short term knock retard then the total timing pulled due to knock at that point would be 5*.

Is that basically it?