Cummins isx pulling rpm

This is not specific to the ISX, but engines haven't been lasting as long as they used to. N14, series 60, and 3406 were all million mile motors. Some of the longevity is due to emissions, but a lot, IMO, is because the manufacturers recommend lugging them. I don't think 1450 is lugging an ISX, so it's up to you. Buzzing it a little would mean you're already in a more effective gear for when you need your Jake.

 

The ISX's sweet spot is 1,400 to 1,500 rpm at 65 mph for linehaul applications.

1700-1900 is high end
Won’t hurt to go to 2100.

 

I've always wondered how the can recommend such low RPM in these new engines. Maybe they are just lower torque? But I agree lugging at low rpm and high torque is a killer.
That said 1200-1300 is about as low as I would go, and that's only if you aren't putting a full foot into it. If you are really pulling hard I'd keep it 1300+. And 1700 isn't gonna hurt a darn thing either

 

I always pulled with the isx at 1600 -1700 rpm and about 20psi of boost...seems to just chug up the hill, without abusing it.

 

The compromise I arrived at was - for fuel economy - to try and run at lower rpm's on the flats (in low torque situations, I have a gauge), but to not be cheap and wind her up a bit going up hills. Especially so when heavily loaded. I have a new 'Endurant' automatic, and actually, 95% or more of the time, it seems to keep the rpm's about where I would, anyway. Which is convenient. But every once in a while I'll go to manual mode to keep it working constantly in a lower gear.

 

Lower rpm requires more fuel and speed will drop on hills. I understand the less revolutions. But not if more throttle is required.

Cruising the mostly flat California. I found 1500 to be better with a .5 bump in economy. I didn't lose much speed on the small ups either. But that was a 16 FL with dd15.

1600 - 1700 is the peak range for isx 450. As mentioned above.

 

I have isx15 450hp and usually cruise at 1500rpm @70mph. I do have 10spd with 3.55 gears

 

Since you're always heavy I say 1500-1700 for longevity. The isx 12 and 15s I've driven liked that rpm range for pulling. (2011-2015 era). Easy as hell to keep it in that range with your 18sp. And turn your fan on at the bottom of the hill, don't wait for it to heat up

 

Back when you had mechanical engines and actually had to be a driver and not a steering wheel holder. Most trucks on the dash stated something like, operating rpm range and DO NOT LUG ENGINE written somewhere visible. Now you have color coded idiot lights