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#1: 10-05-2008, 06:00 PM
*** Knock, do you have any?
 
 LittleBlueGT
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Title: RS4 killer
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I have learned the hard way, and so have a few others. Now that another local has blown a stock block I think this problem should be addressed.

How do you know if your engine is experiencing detonation (knocking)?

-you log it!


Seems simple, but many people miss a few important bits of info. Yes all this info is in threads like Subaru's Knock Control Strategy Explained at RomRaider. But let's make it a bit simpler so even the basic guy that wants a strong running stage1 or stage2 can figure it out.

First myth (that seems to get carried around, and expounded upon from time to time, even by people that should (and maybe do) know better:

"My car is showing positive DA (Dynamic Advance), I guess all is well"

WRONG! That statement could be true, but just as easily could be false.

Let's look at an example:

Here is a little log showing DA, I have heard others say, "look at how happy the ECU is, it is adding 8 degrees of timing almost all of the time!"



Here is the exact same log, but this time FBKC (Feed Back Knock Correction) is added to the list of logged items:



Same log, same everything, but now it is readily apparent that at 5219 rpm the ECU heard what it thought was a knock event, and pulled 2 degrees of timing as a result.

That same info could be seen in the first log, but it is a bit harder to see. First of all I know that my high load DA table is all 8s, so at high load if my DA is anything but 8 degrees, I know there is a problem. Second, one can graph out the timing, and from there it is easy to see that the ECU pulled 2 degrees of timing.

"But it was easy to see the pulled timing, even w/o logging FBKC.
"

In this log that may be true, but it is not always that easy to see. For one thing, not all tunes are set up the same (not saying one way is better then another). This can get more complicated, but lets just leave it at that.

I think for the "Joe Blow" that just wants to quickly see if things are safe it is much easier to log FBKC and be done with it. Of course one should also make sure their IAM is at 1.0, and it is a good idea to look at one's learning view. All are addressed in other threads.



Cliff notes:

1) log or learn how to log, or have a buddy log your car, even if you are just running COBB stage2 (our gas doesn't even like COBB's tune)

2) if you only have COBB logging ability, then learn how to read the logs properly to determine if there is any knock.

3) RomRaider is the best tool IMO to use for logging, use it to log FBKC

4) if FBKC is 0 for a WOT run, IAM is at 1.0, and your learning view loks clean, then it is pretty safe to say your engine saw no knock for that logged run


Hope this saves a few blocks.
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