Is it possible to lug a truck at peek RPM?

Your engine will have peak torque beginning at 1200 rpm. It will be your decision if you want to go below that. You will start losing pulling power below that point.

 

It's a modern engine as long as you didn't do ECM programming it will protect itself with its safety derate features being a 2009 1200 to 1500 you will never hurt it. Least that's what I was told on my 07 which ran to million plus before trading it

 

Just curious what your comfort zone is as far as pyro temp goes? Not sure what your engine is, but supposing it was a rebuilt, reflashed single turbo mbn C 15?

 

Stick a pyrometer in there.

 

You can pull down to 1200 and climb at 1200 constantly with no problem. I run my Cat between 1150 and 1400 all the time. If I let it go below 1200, it's either because I'm on flat road and empty or I'm pulling a hill but just about to crest the top.I also watch the EGT gauge( shift down if it hits 1000degF). My ECM safety parameters are off so it will not reduce power automatically to safeguard the engine; I have to watch gauges. Most engine ECMs will cut power when it gets too hot. Maybe someone can post a torque chart for your 07 Cummins ISX. I think it's peak torque is 1200-1500 like a C-15. The newer engines, like DD15 pull down to 1000.

 

That's at full power you're talking about. You can run along at 1000 rpm on the level or downgrade at low or no boost. If the work of the engine only requires 100 horsepower you could run at rpms lower than peak tq and hp and only using enough fuel to keep rpm steady and it wouldn't be considered lugging.

A good rule of thumb is if the engine can build speed just by adding more fuel you aren't lugging it.

Of course if your engine has fuel settings over stock you can risk building too much heat.

 

well at 1400 rpm up hill im floored...i cant add more speed by stepping on it, but its not falling....thus i think its not lugging and the motor just sound like its working it but off.

 

Sounds like peak rpm is really just peak speed limiter. I have yet to see and heavy diesel with a peak rpm of only 1400, and it is hard to imagine that someone tweaked the ECM to limit rpm at 1400 across the board. But, stranger things have happened when some idiot in a cubicle at a fleet gets an idea in their head. Is that 1400 limit in all gears? Another thing that crossed my mind, it there is a progressive shifting thing in the ECM that, when turned on, will limit the RPM's for shifting purposes. It could be that also. But even the lowest I have seen with that setting on is 1600 rpm. Each engine is different.

 

I mean, it normally slows to around 1400 from cruise speed. It normally cruises at 65 mph which is 1525. When I go up a relitivly seep it it cant hold 65 normaly but unless its real steep it generally stops dropping between 1400 and 1450 depending on the grade. ON the flat i can get it way over 1400.

 

When schneider got their first cascadias with the dd13 they neutered the crap out of the rpm band. i think max rpm was 1600, but they would basically derate power above 1300 so any hill you came to youd instantly drop to 1300 rpm and heaven forbid you had to drop a gear and the next gear would bring the rpms up to 1500 youd again instantly drop down 1300 rpm from the derate.