Thanks Scott that makes sense. Still kinda torn on injector size, turbo size and what one to do first? Been doin quite a bit of research and so far I've found the most agree on too much fuel is better than too much air. However, that comes with the price of high EGTs and high boost numbers. Now is this a true statement or one of those it is but...kinda statements.

 

OK - diesels run hot on fuel, not air - so you're better off with excess air unless your primary goal is power production.

Drive pressure - or Turbine Inlet Pressure - is the average PSI found between the cylinders' exhaust valves & turbo's exhaust volute, and as such is a indirect indication of the amount of work (drive HP) available to be exerted on the turbine.
More is better, unless you already have enough - that's why inducer/exducer size, exhaust housing A/R & wastegate selection/tuning is so important... excessive TIP costs power, especially at RPM.

Depending on which injectors you get (significant fuel economy difference between extrude-honed & EDM'd tips at the same HP increase), good fueling software - i.e. Smarty - will allow good mileage & durability out of the engine when you're not leaning on it.

Injector longevity is almost always compromised by 2 issues:
1. excessive rail pressure from stacking fueling boxes & software, running a rail cap, lifting suddenly after a hard run, etc. - great ways to blow tips of the bottom or solenoids off the top.
2. WIF corroding their internal parts, or WIF-generated fuel system detritus filtering out in the bodies' internal clearances.

The HE351 already on your truck would make a good secondary in a twinset - you can pick up an non-WG S400 frame primary on the cheap and either massage the Holset's internal gate to manage the extra drive pressure or use an external gate... with some interstage cooling (actually, your AK temps might do it already!) your goal of 7XX RWHP is readily attainable.

Swapping out the OEM passive-EGR bumpstick is very helpful - it's the gift that just keeps on giving.

Choose your stall speed after your turbo(s) are finished - tight converters & slow spool will keep the truck parked more often.

Make sure your lift pump's water filter flow rating can keep up with the pump GPH - otherwise you'll likely be dealing with a water-in-fuel injector issue at some point.

Also, besides developing much more clamp load, 625+ studs will hold their value far more than anything else - either to you, season after season, or to someone else if your build should change direction.

 

We have a few trucks running 90hp nozzles and a Silver 62 Turbo. Great Power and Fuel Economy.

 

what kind of egts are they seeing? I currently have this turbo and am running 37's. I have 4.10 rear gears and a 6 speed. Thanks