There is one thing about your dyno sheet that has me concerned before condeming the spark plugs. Looking at your sheet there are two runs, one note mentions "NGK with previous timing table and stock AFR Timning table", then the second runs note mentions "TR6 NGK & stock timing". It appears to me that during both runs NGK TR6 plugs were used and only the timing advance was changed. So was it actually a plug swap that corrected the excessive KR or was it a change in the timing map in the engine calibration?

If too much advance is added to the timing tables either by the main timing table or via the AFR timing correction table which is an adder during PE (power enrichment) during WOT, either way can cause detonation, and once it starts it can increase in intensity quickly as chamber temperatures climb. I use a lot of TR6 spark plugs and have not seen KR caused by them. If the wrong heat range or the wrong type in electrode/insulator combination is used in certain types of applications it can cause excessive knock and the resultant knock retard.

For instance for higher boost applications I like to use a plug with a shielded electrode such as this:



It is a NGK plug with the same #6 heat range as a TR6 however its electrode is shielded as you can see in the picture. Its not hanging out in the chamber as with a standard TR6 exposed to chamber heat where it can get damaged or become a hot spot therefore causing preignition. This same type of plug is used in heavy duty truck applications as well. Years ago as a tune up tech in a dealership I used these types of plugs in various passenger car applictions when the complaints of detonation would come in. Droping the heat range and going to this type of electrode/insulation design cured many causes of detnation complaints in the early 70s in the early days of the then new catalyst equipped cars that were running leaner and leaner fuel mixtures.

Personally I don't think the problem with NGK TR6 plugs is very common. There have been instances of an aftermarket plug causing charging system errors, and there is even a TSB about this. But the TSB mentioned some other type of aftermarket spark plug, if I recall its one of them gimmick plugs with some kind of flux capacitor built into them Aside from that I haven't seen any causing excessive KR, at least not in my shop.

 

See Tom you know to much!

The first run is indeed TR6 plugs, the run with timing removed from stock timing tables to correct the Knock when the stock plugs were being used. That run was to verify nothing changed.

What did change was all the minor knock that was still going on went away.

Run #2 all the timing tables were returned to stock, in other words the timing was advanced back to stock. Just the way the car was originally calibrated. Hence "TR6 NGK & stock timing"

The originally post I responded to referenced minor or lite modifications, a pure stock vette may not demonstrate what I have shown. My car has a modified intake manifold, TB & a Venom intake.

My point to this is that the average driver would never know the timing was being pulled & the power reduced. Most also do not have access to tuning software to correct timing or more likely in this case correct the Burst Knock, Attack, Retard or knock sensitivity tables. It seems from the other site HPT the LS2 & 3 motor's are very fussy regarding knock.

A simple colder heat range plug did wonders! No smoke or mirror's, they did "not" make more power.

Now to a far more important question how is my 416 coming along for the C5?

 

You sold me on the TR6's, now what about gap. The car is and LS2 CNC'd H/C and the L76 intake, Kooks, Vararam, etc. I have been running TR55's gapped at .50 but I'm thinking about the 6's gapped at 45-46. ??

 

I just run the stock gap.