Knock sum vs Knock voltage

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colt92t
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Joined: Wed Apr 18, 2007 7:39 pm
Location: Canada

Knock sum vs Knock voltage

Post 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?
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colt92t

tlcoll1
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Re: Knock sum vs Knock voltage

Post 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

colt92t
Posts: 9
Joined: Wed Apr 18, 2007 7:39 pm
Location: Canada

Re: Knock sum vs Knock voltage

Post 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?
colt92t

tlcoll1
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Re: Knock sum vs Knock voltage

Post 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

honki24
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Joined: Thu Nov 17, 2005 9:59 am

Re: Knock sum vs Knock voltage

Post 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.
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