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MadMaxHSV
September 10th, 2009, 05:15 AM
I've noticed as many seem to have, that even with the stock tune i'm logging knock retard.

I've just finished doing an AutoVE Mafless tune which is fuelling nicely, but for now i've re-enabled the MAF but still open-loop.

Even though the fuelling seems fine and i'm on the stock timing map i'm still getting knock (which seems strange with high octane fuel and stock timing).
I'm on an LS2 with the E40 ecm, running 98 octane fuel.
The only engine mods are a set of 1-7/8" longtubes (high-flow cats and 3" catback)

Reading around it seems this may be the oversensitive knock system at work but i'm fairly new to this and want to be sure.

Attached is a log from one drive around the local bypass. I'm picking up retard on both GM.KR and GM.KNKRET.
A good example is at timestamp 10:46:09.874 getting 3.8 degrees retard at 11.77 AFR and 21* spark pulled to 17* at 4759rpm

Is anyone able to have a look and see if this looks like false knock, or something to worry about?

Many thanks

ringram
September 10th, 2009, 08:26 AM
A wise Ozzie once told me that unless knock is sustained and therefore sawtooth in shape then it may not be actual knock. That big spike a little later on for example looks like nothing to worry about.
Most of that looks fine to me. Your AFR is a bit rich for NA though dude.
If you lean it up a tad you might need to drop a little more timing out. I picked up 10% more rwhp going from 11:1 to 13:1
You will never get rid of all logged KR in my experience. You will get the odd weird tick now and again. Its Mr Sawtooth you want to avoid which shows timing being pulled and added as knock is detected and decayed back out etc.

MadMaxHSV
September 10th, 2009, 08:48 AM
Cheers Rich, I won't worry too much then. May try reducing the knock sensitivity or is that wise?

Was happy keeping the AFR a bit rich until I squared my VE and checked everything else was in order (like no knock :) ).
Got SD running quite well now. Time to start leaning it out.

ringram
September 11th, 2009, 06:45 AM
You can make spark recover faster. You can try detuning, but Id be tempted to look at recovering faster and making sure you have no sustained knock at any point. As you lean out you might want to keep an eye on things in case it pops back on the radar. But when you get real knock it will look like a circular saw tooth type of thing. You can also make it pull less out when it does detect knock.
That would be better than moving towards making it deaf to real knock IMO.

Let me know how you go comparing SD vs MAF for throttle response etc.

MadMaxHSV
September 14th, 2009, 11:36 PM
I need to try some more back to back comparisons between SD and MAF.
Not seeing anymore knock with the leaner PE commanded, so ok for now.
I might bump the recovery rate and see how I go.

ringram
September 16th, 2009, 07:45 AM
Get some dyno time once fueling is sorted and play with spark.
Use bidirectional spark and hold a timing cell if you can (or if the dyno operator can)
You can actually pick up power by reducing timing at WOT sometimes.