E63 caput @ 43k 🙄

[jimjamiejames]

The misfire occurs at high revs with full throttle, initially only in one of the two hottest-running cylinders, No. 1 or No. 5. The cylinder I had to have bored out and linered, with the most bent conrod, was No. 5.

Which would go along with what jobsworth said and the hot exhaust igniting the unburnt fuel.

 

[Bellow]

Here’s what I think happens. The piston rises to the top of the bore on a compression stroke. The direct injector is ready to go, squirts in the fuel. The spark plug fails to fire. The air fuel mix stays there as the piston is dragged down by the rest of the engine. Piston begins to be driven up by the con rod for the exhaust stroke carrying the unburned charge still there in the chamber. The instant the exhaust valve opens, even the tiniest smidge, the charge is lit by exposure to the hot contents of the exhaust manifold. But the piston is still coming up the bore hard to push out the spent exhaust that should be there. The narrow top of the con rod doesn’t help here. The rod is exposed to uneven pressure from an uncontrolled burn and it tweaks.

No disrespect Jobsworth but I can't believe that there would be sufficient pressure to bend a rod as the pressure can vent pretty freely to atmosphere via the open exhaust valve. Unless turbo back pressure and the influence of another cylinder exhausting into the manifold at the same time tips the balance. Maybe why cylinder # 5 is most susceptible? Only supposition on my part though.
Unburned fuel will potentially wash the bore of oil though.

The misfire occurs at high revs with full throttle, initially only in one of the two hottest-running cylinders, No. 1 or No. 5. The cylinder I had to have bored out and linered, with the most bent conrod, was No. 5.

I remember going through all the possibilities at the time of your failure but don't remember the conclusions reached.
A casual look at the videos reminds me there was debate as to where the rod was restrained (thrust washers small or big end).
For certain, on turbo motors, unwanted oil in the cylinder (from incorrectly installed guides?) plays havoc. Pro-detonation the ECU retards timing which leaves heat in the cylinder that should have been better deployed in expansion. Oil getting past the rings in smart fortwo engines leads to them burning exhaust valves. Pistons are also exposed to more heat.

 

[Muckypaps]

So my car has a crap engine.
I have 10k before it pops.

 

[E55BOF]

No, and unlikely, in that order, but the last bombproof - or almost - V8 engine MB made was the M113. Which engine do you have, and what mileage has it covered?

 

[Muckypaps]

M157 981
37k miles
I was only messing, I have faith.

 

[E55BOF]

So have I. And hope too, just in case...