ISX 475 vs. ISX 400 ST

compare CPLs. Part lists are different, turbos, injectors...

 

The ones we get here have the same peak torque.
I don't if the know torque curve is the same.

 

If you are loaded heavy , run fast or drive in mountainous areas you will.
On relatively flat ground with light loads under 65 the difference will be negligible.
Unless you are using more then 400hp to propel the truck you won't notice , it in nice to have it in reserve though.

 

The big deifference is the ST in the name. The ST stands for Smart Torque. What you have are two different peak torque amount during operation. For all of the gears except the top two would have for example 1450 or 1550 lbs ft of torque and then you might have 1650 or 1750 lbs ft of torque in the top two gears. It is for fuel economy reasons. I have been able to tell the person that owns the truck what the torque rating of the engine is when I drive it. You can and will feel a difference in the performance between the two trucks. The torque curve is similar, but not the same on both ratings. Also you will not be able to upgrade the 400hp to 475hp without mechanical changes to the engine.

 

There are CPLs for every engine. According CPL I choose calibration file to let engine run properly. Some "smart" guys use to put 475 HP calibration to engine that was designed for 430 HP maximum!

 

Smart Torque is sometimes programed in to engines for the sake of the drive-line when in lower gears.
No good uprating an engine if the rest of the drive is already at its limit.

 

Don't worry about the driveline. Unless it's out of a pickup 100hp isn't going to blow things apart. There are plenty of guys with 700hp to the ground running a driveline ordered for 475 with no catastrophic failures. The way you drive makes all the difference.