Cummins isx 15 dyno graphs or charts

Can't help with specifics, but maybe try asking them to increase TQ up to 1850 , instead of asking for more HP. Some boss,s think oh he wants more HP so he can rev the #### out of the truck, but ask for more TQ and they think oh oh maybe he needs more power, it's just a mind game thing !

 

your running way to high in the rpm's they pull best right around 1350. downshift at 12 up shift between 15-16. they govern out at 2k start cutting back fuel around 17

edit i did miss read your post a bit on the 1600tq and 450 hp the lowest hp ones iv drove is 475 and 1850 check your valve cover for what rpm peek tq is as and that is the rpm you will want to let it chew down to before grabing a gear down. being as all the isx's iv drove were all 1200rpm peek tq i would assume yours is the same but all the ones iv drover were at 1850 tq with my current truck set at 535hp previous set at 565hp. no issues pulling after getting a few miles on the new truck it was a total dog with no tq for the first 5k miles or so till the computer started giving me some power seems to keep getting better the more miles i get on the truck

certainly see if they will bump you up to 1850 tq thats where your pulling power will come from

 

also check the literature that came with the truck i haven't been bored enough sitting in the truck to read any of it yet. but from another driver with a new truck in our company told me that it explains rpms and how if you spend too much time over revving or lugging the motor it will hold back giving you power longer as to protect the engine. and increase the hp in different intervals until the motor reaches the end of its break break in program somewhere around 20k miles. this i have noticed my self as i get more miles on it she defiantly has picked up quite a bit of power mostly in tq from the feel of it. when the truck only had 1500 miles on it, it would fall flat on its face as soon as it saw a mole hill loaded at 100k+ now it will pull hills just fine. also seems to be getting up in the mpg per the display it has picked up almost a half a mile per gallon sense the last noticeable increase in power.

 

http://youtu.be/LmNTjfm4cwM

 

The highest torque rating that you can get for that engine family is 1750. Peak torque is at 1200 rpm on that engine. Peak HP is at 1800.

 

I dunno...there could be something wrong if it's taking you so long to build road speed. I've got a 525/1850 ISX, and I can get up to speed every bit as fast- if not faster, by working the engine between 1150 and 1400 rpm, instead of working it in the 1600 - 1800 rpm range. Now, I'm grossing 85,500 which is far from 100,000+, but it's heavy just the same. My experience is pretty much the opposite of yours. All I seem to get at the higher rpm's is a bunch of noise and high fuel consumption. Down low though, it feels like she will plow through a brick wall and barely use any fuel doing it.