Quote:
Originally Posted by Gaz64
Any more pics of those pistons Ed?
I find it hard to believe the top ring is fitted to that piston, I can't see it.
The engine must have pinging a lot, intermittently.
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That was the only one I kept, Gary. They all looked about the same. The top ring is no longer in the land in that pic. I know, the visual is stunning. Amazingly this engine did not smoke and still had significant power. The second ring was apparently doing the majority of the heavy lifting — not something it was designed for.
Unbelievably the detonation was undetectable to the ear while driving the car, windows up or windows down. It was however, just enough to overheat the crown and top land but not enough to push out a chunk of piston or burn through a ring. The other thing worthy of noting was the engine literally ran 30K+ miles with this condition after being tuned by a big name shop.
The tune was reportedly done for max power. The engine did not have any knock detection or correction protections / capabilities because it was an OEM ECU. The car was a supercharged 03 Cobra which made the engine more detonation prone. I believe it would be difficult but not impossible to do the same thing with an n/a engine — but who wants to test those sorts of waters.
The old lean is mean quip sounds good but does not play well in the real world. I always like to shoot for a whisker on the fat side just for good measure. That does not produce any meaningful decrease in power but it does produce a significant improvement in engine service life.
Ed
p.s. Almost forgot to mention, the second and
oil lands were both tightened up a bit . The second ring was quite tight essentially keeping it from freely rotating on the piston. The
oil land was also slightly pinched but not enough to limit ring rotation or compromise
oil control yet.