Ah, this isn't a question I can answer formally as a moderator, as its up to players to decide how to best use their engines
However from a personal point of view, I would suggest to keep it simple.
While you can tune your engine for every individual circuit, that doesn't do you much good if its just mashed on top of any old car design. You need to consider the bigger picture, and the circuits characteristics, often the strength I select for a track each season will change depending on what stage of the season I am at, and how I wish to balance out my car for that circuit.
I tend to work by the starting principle of "if in doubt, go for acceleration". However as you are in a No Refuelling league, it might be worth thinking about fuel economy.
