Here's the story:

I've been experiencing pretty bad tip-in audible knock between 1800-2600rpm, I'd cured the issue by reducing timing to the point it was 5-7 deg BELOW the stock table...but this seemed a rediculous solution because if the factory can get away with that timing I REALLY out to be able to (I DO have a higher CR but the factory timing is pretty tame). I've finally been able to get my knock sensor sensitivity set right so that REAL knock is pulled but false knock is eliminated.....by temporarily reducing the max KR table to zero I was able to tell that I'm actually REALLY knocking audibly, now I had to figure out HOW to fix this tip-in audible knock issue.

Since there are three issues going on here I had to eliminate them one at a time:

Fuel - I'm not in PE when this knock is occuring so that's not the issue.

Spark - If the factory can run this timing I should be able to as well....

Air - Throttle transitions use the VE table....I've tuned the **** outta that so that's not the issue (or is it ??), Oh...I *may* have found my issue. I started out by logging KR but instead of logging the RPM vs. Main Spark tables I logged is as RPM vs. VE to see where in the VE table I'm getting knock - BINGO !!, there was an area on the VE table that was a "valley" EXACTLY where I was getting knock !! I interpolated that area between points that I knew were good and suddenly my tip-in and transition knock is gone !!

I had *thought* my VE table was good because of all the tuning I've done to it, but apparantly I'd missed something.....

 

Excellent detective work! I like the fact that you methodically diagnosed the problem and found the root cause, instead of just throwing more mods at your truck.

 

Classic!!! I read a thread back in the day on ls1tech about a guy doing this and figuring out the "holes" in what appeared to be a solid VE table (turbo guy as well, maybe not twins though LOL). This should be added to any VE tuning scenario. Smoothing and even hand smoothing will miss those small dips! Congrats. Informative.

 

yes, very informative as I am havis this same problem right now. I get up to 8* of retard at 2000 rpm@ .60 g/cyl.

I inoticed after reading this thread that I too have a valley in that area, and I have reduced timing to 10-12*.

Thanks for the thread!

 

Hmm logging KR on a MAP vs. VE

Now thats a idea i never thought of before, cool tip