Computational budget vs. computing budget vs. computation budget
Let's look at the dictionary definitions:
Of, relating to, or using computers.
the use or operation of computers.
the use of computers, especially as a subject of research or study.
So computing is a narrower field than computational, and is pretty much the same as computation.
You are talking about the time required to run on a computer, so I would say that Computing fits best.
The computing budget is 11 hours
budget doesn't really fit here.
allow or provide a particular amount of money
it is specifically referring to money, and you want time. Maybe allowance works better:
the amount of something that is permitted
but I would simply say:
The computing time required is 11 hours.