The matrix collapsed. But it really did totally collapse. At the end of the return leg, it wouldn't go over 30. (Yes you're right-melting a ceramic would be a hell of an achievement!)
I wouldn't have thought that was possible in a closed-loop fuelling system ...
I was surprised but not once I thought about it? Don't forget, the hottest flame is a stoichiometric one ie closed loop. Combine short gearing pushing the RPM up to about 4500-5000 at 70 mph +10%+1+X, and only a single exhaust valve and the EGTs were probably over 900C. Turbo petrols run rich to keep temperatures down and often EGTs drop at full throttle.
It might have been frequent lifting off that did it (no overrun fuel cut off). Interestingly, the engine was not distressed, no audible pinging, no overheating, no loss of power indicating heavily retarded spark timing. Compression check was fine-no burned valves. It wasn't a MAF/lambda problem either. Only the cat wa replaced and it's sailed through emissions ever since.
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