Engine model numbers are as much defined by marketing as by engineers.
In other words if it's different in any way capitalize on the difference with a name change. However if a model is selling well and a completely new name would sound different, then it is not a good idea, so just add a small change like a -1 or a "b" after the model.
The general public (non buyer) would never be expected to sort this out logically.
I believe that this applies to auto engines as well