Ram HD 1000 lb-ft MPG loop

ShinerBock wrote:
Loaded is even worse with these two. If loaded to max 26k GVWR, it takes a over 200 hp just to move that much weight at 65 mph(which is the speed most of these trucks are governed at) up a 2% grade hill. So the 200 hp engine would be foot to the floor under heavy load pegging it's governed speed of 2,600 rpm on just about every incline. The 325 hp version not so much. Since it makes 750 lb-ft at 1,600 rpm, we can do the math to deduce that it is making 228 hp at 1,600 rpm allowing the truck to perform the same work with less rpm and it does not require the driver to push the pedal to the floor putting the engine under max load most of the time. In these conditions and truck applications, the 325 hp version is much more reliable.

From now, I'll address ONE point at a time to make our discussion more useful. Also be nice to stop getting personal and focus on technical matter.

You've done this before - when comparing two engines, you have to keep all other factors CONSTANT. So if you compare the engine life of a 200hp ISB vs 325hp ISB, compare both at 100% power output.

Obviously if you took a "700hp" ISB, operate it at 50hp, it'll out live a 200hp variant at 100% power output.

In addition, I can give you a whole bunch of reasons why an ISB making 750 lb-ft @ 1600 rpm can have higher EGT/ECT/IAT due to higher air/fuel mass, and therefore creates more wear, than an engine making 404 lb-ft @ 2600 rpm (also by math, for a 200hp engine)


Have a look at this:

https://www.cummins.com/engines/isb-epa-07?v=241&application=Transit%20Bus

Is it by chance vehicles with the lowest duty cycle / expected hrs (Fire trucks / RVs) have the highest hp rating, and city buses that experience the highest duty cycle (aka "foot to floor") have the lowest hp rating?

Again, these are all EPA 2007 certified, so emissions is irrelevant. That answers your proof for "higher hp engines will not last long in the truck applications"