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Positive and Negative Knock retard?

Practical Reflash Tuning

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Discussion and questions related to the course Practical Reflash Tuning

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dear fellows,

i‘m tuning my mazda3 skyactiv 2.0 recently.

After some data logging,i’m not sure about the real meaning of positive knock retard and negative knock retard,which means to pull timing out ,while the other means adding.

need your kindly help.

terry

PS here is one of the logs with positive knock retard.

Attached Files

This isn't an engine that I've tuned before so I'm not familiar with the software. It could be that this is the Mazda ECUs way of retarding timing when knock is occurring and advancing timing when no knock is present. Many ECUs have this sort of functionality to deal with varying octane of pump fuel. The ECU can constantly advance and retard the timing to match the octane of whatever you've put in the tank (within reason of course).

If you can't find any information about this from your software supplier then logging the actual ignition advance and comparing this to the knock advance/retard can help you see what's going on.

hi Andre

thanks for your reply.

let's go a little bit further,what does "KCS learning value" means,i didn't find an exact answer from google.

good day

Did you look through all the documentation for the tuning software?

The KCS may indicate a learned octane adjustment or calculated octane rating.

hi arghx7

thanks a lot.

the tool has no instructions at all....

It's always dependent on the specific platform but I'd say the KCS Learning Value would be the final feedback from the knock control system which represents the final adjustment being made to the base ignition table value.

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