What do these mean? What is the 5.9 ?

 

The "ISX" is the 15 liter cummins highway engine with DOHC. I know that the older 5.9's were called "ISB"s, but I am not sure if the newer ones are still called that. Hope this helps a little.

 

The ISB is the 5.9L. ISB stands for interact system, b-series. all 98.5 and up 24 valves including common rails are isb's. also, the 3.9L 4 cylinders are considered ISB's.
12 valves are 6bt's, and older 3.9L's are 4bt's
ISX is a 15L x-series engine in heavy trucks.

i'm pretty sure that "IS" means it's computer controlled, if that's an easier way to think about it.

 

Thanks!

 

Here's some more info I just found(if anyone else cares!)- What Is This Interact System? It's a new engine design platform that combines sophisticated electronic engine controls with high-pressure fuel injection and high-strength componentry for an engine that outperforms every competitive diesel on the market today.

Describe The ISB In 15 Words Or Less. The ISB is a fully electronic, 4-valves per cylinder, in-line 4 or 6-cylinder turbocharged diesel.

 

The Common Rails are ISBe.