Page 1 of 1

Knock sum vs Knock voltage

PostPosted: Mon Apr 19, 2010 11:53 am
by colt92t
Hi all,

I want to know to correlation between knock sum and knock volt because in my logging I can see very high knock sum value when I have very low knock voltage?

Re: Knock sum vs Knock voltage

PostPosted: Tue Apr 20, 2010 9:20 pm
by tlcoll1
There's no direct correlation, but usually high knock sum corresponds to spikes in the voltage. I'm not seeing that on your plots, though, unless you have smoothing turned on on that plot. With knock sum available to log, I tend to use that exclusively, as that'll be the thing that causes timing to be pulled.

Tom

Re: Knock sum vs Knock voltage

PostPosted: Wed Apr 21, 2010 7:13 am
by colt92t
Yes I see spikes (max 1.0) without smoothing, but I was staying in mind that the knock voltage should be higher then 0.x for the ecu start recording some Knock sum. So, this is normal?

Re: Knock sum vs Knock voltage

PostPosted: Wed Apr 21, 2010 8:55 pm
by tlcoll1
In general, the voltage will increase with RPM. Think of that as the "background noise." The spikes are the real knock events, which the stock ECU sees. As I said, I'd just look at knock sum.

Tom

Re: Knock sum vs Knock voltage

PostPosted: Tue May 04, 2010 2:12 pm
by honki24
FYI with EVO ECUs you can log the knock voltage threshold too, so you can see when you're going above the threshold (which moves) a corresponding knock count is assigned depending on how much over you went and how quickly the voltage ramped up.