LNF false knock (kr) and how to tune out

[codename Bil Doe]

After hearing it for the bazillionteenth time, I'm making a thread that is easy to search for.

False knock occurs because torque-based ecu's use kr as a catchall for something it's programmed to not like.

I race with up to 25 degrees of peak timing with zero knock. It's not what LNF's just do. It's because someone didn't know how to fix it that they said that.

Below 190 degrees ECT (I won't go specifically into how it varies and reduces response as the temps climb) the ecu will input false knock immediately until the engine is up to operating temps. On my 2007 this means a solid 3.7 deg of kr that will hold as long as there is any pedal input. On my 2009 it would mirror pedal input. Fun to play with.

Once the engine is above 195 deg ECT the engine will input false kr any time there is steady pedal input but the timing dips. Go to the point of kr at part throttle. If there is a dip in the timing, note the load and rpm at which that dip occurred. Raise the timing in that cell 1-2 deg until the timing is flat in logs. Your false kr will disappear. Same with dips at wot. Make sure to smooth the table after changing.

The ecu does not like seeing any sharp changes in a table. This includes wgdc, cam and spark timing, dal, etc. All tables must be smooth.

Your logged timing should be completely flat. I'm willing to bet that 99% of the people on here could log a steady 10% pedal and see their logged timing look like a saw blade.

[lt1z350]

I have been saying that for a while that this style and the ltg like my caddy uses kr as a total catch all. I also have experienced in my logs up to 8 degrees of kr but yet timing is still climbing at the point of knock and that alone tells me the kr is from something else like over boost or some other parameter going out of wack. It's weird sometimes I can see delivered torque cross over demanded torque but yet all my tables are set at max so obviously not the torque but something else or a table we cannot access. Point being when I see this next movement on the log 6-8 degrees shows up and a timing change to lower boost and bring back in line. I don't see much throttle closing ever but the kr controlling all the things that stock would shut the throttle. And yes log normal driving and the stock timing looks like a saw blade with broken teeth on it. Same with cam timing where I guess your point being just smooth over these tables will help the conditions. Well before the ltg I see you guys have been have been fighting false knock or kr readings due to other things making it show up. 3-4 degrees cold like u said is big and I never put together possibly retarding timing to super heat the exhaust and engine by using more retarded timing. Good post and will give your theory a try this weekend.

[lt1z350]

Was thinking a little more about this and not sure if yours has but the ltg under engine > torque management >fast torque exit. From what I understand fast torque are things like fuel cut and timing cut. The table has a value at lbs torque. Say 37lbs explanation says when torque exceeds this value fast torque exit will enable. So pulling timing or fuel to pull back torque where could see false kr from over torque situation. I have set this on mine to 370lbs but didn't experience the changes I had hoped for and maybe due to my tables still choppy. If someone knows the lnf has this let me know and your experience with this table please. Going to smooth some stuff and do what bill said and see how it works out for my ltg this weekend.

[KLUG'S SS]

I do know on my CTS which has the 3.6 DI motor and the same E69 as the LNFs I have had a ton of false knock issues as well. I've done A LOT of smoothing to my spark tables and still seeing the false knock all over hell! As codename Bil Doe said in his first post about all tables being smooth such as cam timing etc.... so I guess I need to address some other tables and go over some of my logs with a fine tooth comb looking for the timing dips like he has stated.


I know compared to many many MANY LS applications I've tuned over the years the timing tables in these Bosch pcms look like CRAP. Just very rough and all over the place really, in my opinion. Looking at any timing tables in pretty much any LS powered car or truck in the graph view or even the table view you can see how smooth and predictable the timing maps are. Not my car in the stock calibration!

[lt1z350]

Have you verified that the logs are not pulling timing when the kr is present? Just curious if yours is acting the same way as mine do. I never hear knock or pinging which I know sometimes you won't. I don't have any signs of it on my spark plugs and have gone as far as bore scoping the cylinders and looking at the top of the Pistons for it. Since I run meth they are very clean so can see everything and no pitting at all. I have also read the lnf guys were clocking the sensor and seeing less knock at 9:00. It's frustrating as it freaks you out when u see 6-8 degrees and only running 2 degrees at wot and I have a generous shot of meth to help with al that and still shows it. So this weekend going to smooth tables and add timing and see how it likes it since this engine is so far down on timing compared to any other combo I have run or read about.

[lnf-efr-6758]

I have attached a log of my LNF, and would like to clarify what Bill is asking to do before I go ahead and make changes.

This is not my tune. The car runs beautifully and with a ton of powwa but I still have that dreaded KR. If I am reading the OP's directions correctly and referencing this log, I would want to add a degree or 2 at 110% engine load at approx. 2600 rpm - I am targeting frame #5045 in the log for an example. Then smooth the adjacent cells as good as possible.

For the past year, I have been trying to deal with this frggin annoying situation. What really frustrates me is that in most cases the KR cannot be duplicated at the same load and RPM. I have tried all types of mechanical measures along with tuning, but nothing seems to work. I've even run 118 octane race fuel!!!....that didn't work either!

Bill...If you are right I will be ecstatic.

Any input or comments are welcome.

Edit: Not sure if this matters in this subject, but am running 93 octane - EFR 6758 - Forged pistons & rods.

[lt1z350]

I had same issue on my ltg and once I went through and smoothed out the timing table I got rid of 90 percent of it. I get 1-2 degrees here and there but it doesn't do anything so don't worry about it. I also went up a lot in my tables. When I smoothed I always went up were I could and total I have gained 5 degrees so far with no kr wot. I get mine at light loads but very little now. Funny it is almost always 1 degree at 4400 right were my peak torque is logged. So try that first smooth out that table so no drastic changes at all from one cell to the next. Mine has no more then 2 degrees change anywhere in the table now.