Different ISX power levels

[Rawze]

The ISX15 engines generally seen from the factory within 2 tiers. Mid-tier 400 - 515 hp and above 525HP+. At 485 and below, definitely tier-2. At 500 - 525hp, it may have to be looked up by engine ser#, and above 525hp is tier-3. The 2 different tiers have different injectors, cams, and slightly different compression (but same size) pistons. Everything else inside them is the same like crank, bearings, etc.etc.etc. - I am also told that some of 2250 and 2350 ISX's have different exhaust impellers in the 451 turbo that comes with them, though I have not confirmed this myself.

There are no factory programs to put a 400 all the way up to say, 600HP, but even the 400 ISX can be set easily enough to 600-HP with a custom made program, but doing so has a steep cost of component longevity.

Adding power to a mid-tier engine is not the same as adding power to the higher tier engine. Sure the smaller engine can do it with no troubles, but it takes a bit longer for the fuel to get into the cylinders, they have a bit less valve opening time (they did this for for improved emissions), etc. making them build heat more quickly + overheating those mid-tier injector tips at high HP levels.

Also, the higher the HP made by increasing torque, the shorter the engine life on any engine. This is especially true of the the ISX due to its short piston/rod design. This higher torque abuse of them mostly comes form truck owners these days who are hell bent on driving them with higher torque settings down in the engines lower rpm ranges (below 1500). It is this ridiculous mentality of high geared rear ends, etc. making it hard on the engine, requiring high torque to get the truck moving. It is the hardest on the liners due to the high internal friction that it creates (short rods + high volatility) by making that much torque at low RPM's.

I.E.> It is not so much the increased HP (within reason) that shortens their life, but the extra torque added into them, especially on the lower end. The 600HP programming is a fine example of abuse, right from the factory. It has 2050 ft-lbs torque in it, but only in the 1100-1300 rpm range where it is very hard on the engine. Those 550+ hp engines live a shortened life when driven hard in the lower rpm ranges because of this.

>> Gearing the vehicle too tall for the application is just as bad. Using tall rear ends forces the engine to use way more torque (and therefore a lot more wear), and not even be able to make full HP. MEga-fleet companies most often gear their trucks too tall on purpose to combat that right foot of their company drivers. Company drivers hold the fuel pedal all the way to the floor everywhere they go.. so the truck is geared waay too tall + governed at 1500-RPM and below.. so that the engine cannot make full power -- artificially saving fuel at the direct expense of engine life.

Mega fleet makes out like a banchee, because they don't care about long term longevity.. as long as they can get it thru the warranty, and then sell it off, abused to all h#ell.. then they win.

The next poor soul looses big-time who buys that truck used, it with a million+ of engine wear due to it being geared too tall and lugged into oblivion at max torque and low rpm its whole life.

The irony is that if a decent driver who does not slam their foot in the floor all day long, is actually more fuel efficient than when the truck is being geared so badly that it cannot get out of its own way. A truck geared with a decent set of rears, where higher RPM can be used and less wear-causing torque, IS MORE EFFICIENT OVERALL when loaded, but only as long as the driver is not abusing this fact, and not slamming their foot in the floor all day.