Do we know what ZJ stands for in power unit type identifications?

Having a chat with someone who believes the 280ZJ is a Dalian product
but I was once told by an engineer in Qishuyan this larger capacity
power unit was the idea of the director(s) of that works in a move away
from the production of the Dalian design 240ZJ. Anyone know for sure?

A few people wondered if the reason for Qishuyan to go to 280mm bore
cylinders was influenced by the ND2s and ND5s in China at the time and
did these designs influence any other aspects of the 280ZJ design.

Cheers

Mark