N14 running 1800@ 75 mph

I have a m11 in a 96 international 9200 with 3:07 rears, and @74 im turning about 1800-1900 rpm, im not sure if my tach is right or not, but it will run like that all day, I was told a long time ago that a diesel engine was designed to run wide open not chopped off at the knees, lol

 

To make money you need to be running between 1350 and 1550, above 1550 you are just burning extra fuel, the higher the RPM the less efficient the engine is and the more heat it produces. The torque curve and the HP curve cross at 1550, that is the RPM the motor has the most HP and the most torque, above that and you are running on HP. That is not how you make money.
An engine has a constant thing that is tied to RPM that is Friction HP, that is the amount of HP it takes to turn the engine at the RPM that graph goes up constantly the higher the RPM the higher the Friction HP. The lower the RPM the lower the friction HP.
Just a thought!

 

John, I mean no disrespect to anything you said.....I just wish to temper the theory with a dose of Cummins reality. He's talkin' about 75 MPH. An N14 is NOT gonna be happy if you are geared to turn 1550 at 75! I have had virtually every incarnation of Cummins from my first Big Cam 400 to a 600/2050 ISX; and I can say with no fear of contradiction that Cummins like to turn. IMO with his setup....the revs are very normal.

 

Just ran from VA to South FL at 6.9 mpg turning 1800rpms. Im impressed. Now to figurw out what I can safely turn it up to. Its a 350 I wish I could turn it to 400 or 435 without burning it up

 

Not so bad, eh??

 

my ser 60 11.1 turns 1800 at 70 m.p.h. all day 16 years now. don't hurt a thing. though I do keep it at 1500 rpms when time is not a factor & stay in the right lane.

 

my truck gets 7mpg all day long whether im turning 1300 or 1800 rpm, just saying

 

If I turn up to 435 would it hurt my fuel mileage? 6.8 with 80k and hills.

 

Another truck that defies science! Where do guys find these magical trucks?

 

ive had this truck for 10 years and it has gotten 7mpg since ive had it, I don't know if its the m11 or 3:07 rears or both, now its not going to be the first one at the top of the hill, but im satisfied with it