bluwtr49 wrote:
As has been said the "sweet spot" correlates to peak torque rpm. In my case the cat C12 is around 1250 or so and is fairly flat to ~1500 so that range is what I consider my sweet spot. ~1450 give me 65 mph so it all comes together nicely.
Find the torque curve for you particular engine and that should help.
If you are a member of BAC there is a retired CAT mechanic that will look up your serial number and tell you the testing data when new. If you already know this sorry for repeating. Being a member won't be an issue for him he is a very helpful guy. Happy Camping!