8.3 rpm for economy?

[Napabavarian]

I've read around a bit and found varying answers, from what I have gathered Cummins recommends 1800, many schoolies are in that range, some say 1750, then I read the RV forums and they say 1450-1475 is the perfect sweet spot, of course skoolies tend to have the 250hp engine and RVs tend to have 300-350hp engine, I'm not sure if that makes a difference, however they do tend to report better mpg, 7-9 vs 9-11 and they would also be heavier.

Thanks for the input.

[Cjgoertzen]

Peak torque on my unit happens around 1600 rpm. I do believe that for me too see better mileage my rpm should be around 1800-1900 @60mph vs the 2200. Keep in mind the sweet spot on the rv's is lower because they use the same engines if im not mistaken and some of the heavy haulers. I am talking the rather large rv's.

[Napabavarian]

Thanks, I was comparing the same engines with different power settings, I see they tend to be in the 8-10 liter area mostly with some 7, 11, and 12s. I wonder if the torque comes in earlier on the higher hp 8.3s.

[Cjgoertzen]

I believe peak torque would happen a bit sooner with the higher hp engine. More hp means more fuel which would light the turbo sooner. Injection timing likley advanced a little sooner aswell.

Just my 2 cents