For future reference, this is my daily driver. I do want reliability. I ran 13,000 miles with very advanced timing and had no problems with it, so I thought that I had a reliable tune.
Anyway, so what I am taking from this is that If I hear something that sounds like metal hitting metal, it is severe detonation and that the pre-ignition is inaudible. That would explain some of the symptoms that I saw on my spark plugs.
Based on Ted's advice, I retarded the WOT timing to 28 BTDC at 3,000 RPM and tapering down to 15 BTDC at 750 RPM and found that the engine felt more responsive. I drove it 800 miles only stopping for gas and the plugs looked as good as new at the end of this.
I also noticed that the engine is much smoother at low speeds (below 3,000 RPM).
My previous WOT ignition curve was completely flat to 1500 rpm (34 degrees BTDC) and tapering to 25 BTDC at 750 RPM.
I am thinking that my original theory was incorrect and that the spark plug erosion that I observed during hard driving was due to pre-ignition, not incorrect plug heat range. The worst detonation that I felt was about 2,700 RPM before (the 90% VE breakover point). This may have also been a contributing factor in the engine failure on the dyno.
Thanks for the advice Ted! I think this information is very good for posterity.
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Originally Posted by RETed
"Hear" preignition?
Not the real early preignition events...
On a dyno, you'll see it on the graph.
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Please expound on what you see on the graph that indicates preignition...
I will see if I can scan the graph of my 5,400 RPM blowup in and see if you can identify the event.
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Originally Posted by RETed
In my experience, EGT's will start to climb when you start to edge into early preignition.
Once you overly advance the ignition timing, then you start to get serious preignition which misfires and drops power drastically.
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Ok, so that explains the drop in power when going to 43 degrees.
What I hear you saying is that the 8.2:1 engine really made 210 WHp at 33 degrees BTDC ignition timing, the extra 6 WHp that I picked up going to 38 degrees was due to early pre-ignition.
I had EGT ports installed on my Defined Autoworks headers, so I will get EGT numbers when I run with those headers on the dyno (probably at least a month out).