The crank pulley design is quite different for MT and AT cars. Is the risk of failure the same in each case?
Yes i believe so. its to do with the bonding of the pulley; as it gets older it like everything else weakens over time.
"The value of life can be measured by how many times you soul has been deeply stirred" - Soichiro Honda
From this side, the crank pulley design looks quite different between the MT and AT spec.
The AT model requires larger diameter in order to spin the ACG at faster rate due to higher current consumption under extended long period of brake light activation such as in the traffic jam.
However, from this end, both looks similar so the bonding method/design is identical and thus, the risk of failure would be similar from design point of view.
However, the biggest factor on pulley weight separation issue is the rapid change in rpm.
Typical example is the frequent sudden big rpm changes during the track session.
Therefore, the owners who track their NSX regularly will replace the crank pulley at shorter interval.
Under normal street driving condition, the rpm change rate/speed/slope would be lower on AT engine than the MT one so it is probably safe to say that AT crank pulley will be generally in better condition than the MT one under normal street driving condition.
Some AT owners in Japan installed 3.2L C32B engine on their AT NSX and regularly tracking their NSX happily.
They are replacing the pulley at shorter interval.
Added to this rpm change rate, the heat and age will play big part and hence, must item to be replaced at every TB service regardless of the annual mileage.
Based on the data I have, I won’t trust any crank pulley more than 10 years old even with just the street usage.
Kaz