Had a couple of people ask me this, so thought I would post it for archive purposes.

On the EVO8 there is 1 knock sensor, this is logged through the #1 knock channel.

These are the following knock paramters:

Knock#1 Raw
Knock#1 Volts
Knock#1
Knock Retard
Knock Fuel

Knock #1 Raw is the raw asynchronous signal coming from the knock sensor. It is sampled continously (at a very high frequency). There should be no need to log this parameter, as it is basically meaningless for tuning purposes (see below for why).

Knock #1 Volts. This is the Knock #1 raw signal synchronized with the ignition events. Basically what this means is, Knock #1 Volts is your Knock #1 Raw reading sampled at each ignition event. If you have no ignition, you don't care about the reading as it is meaningless. Knock #1 volts is what the EMS looks at and compares to the Knock calibration table to give you a Knock #1 reading...

Knock #1 is defined as Knock #1 volts - Knock voltage calibration @ that RPM as defined in the AEM knock calibration. This tells you how far above the noise threshold you are.

Knock Retard is how much timing is being pulled as a result of Knock #1
Knock Fuel is how much fuel is added a a result of Knock #1.

Here are some examples.

Lets say your knock calibration table is setup at 5000RPM to be 2volts.

If Knock #1 Volts is 2.5
that means Knock #1 is 2.5-2 = .5 volts

and so on...

Knock tuning is often a very overlooked area, and usually takes a while to get right on each car, but it can prove to be VERY helpful when done right. It can be setup to mimick OEM configs by altering the knock restore rate, how many degs to pull per volt of knock etc. If your tuner does not spend a decent amount of timing tuning your knock table, please request that he/she does. Its a very nice feature of the AEM EMS, so don't go without it!

Hope this helps some.

 

Ii always log knock #1 raw no matter what.

 

Phillip, thats good that you log Knock #1 Raw, but just know its useless in determining actual knock readings, and furthermore the EMS does not even use it to generate Knock #1. It calculates it based on Knock #1 Volts.

In older versions of the EMS software, there was no Knock Volts / Knock Raw...it was all Knock Raw. But after 1.00 Knock Volts was seperated from Knock Raw.

And, I hope everyone logs internally to tune their knock cal....if you don't you are missing a TON of resolution that the external logging will not pickup in something like the Knock #1 volts reading which changes quite rapidly and requires a heavy sample rate.

 

It's all useless until you've tuned the car on a load bearing dyno and found out what the knock threshold is. But i just log it to follow the trend of increasing noise, then i look for spikes.

 

Definitely! I have tuned 2 cars with basically identical setups, each having vastly different noise tables. Pretty interesting, some motors are noisey, some are quiet!

 

indeed

 

Very helpful info. Thanks Vijay!