This post is just out of curiosity.

One of the advantages of common rail, is the high injection pressures. You're able to shove more fuel through smaller nozzles and get better atomization. Also, because you can have smaller nozzles for a given peak output, you aren't sacrificing much in the way of part throttle drivability.

The LB7 had injection pressures of 23,000 PSI, and the 7.3 is at 21,000 PSI, fairly close. However, for more capacity on a 7.3, hybrid injectors or B codes are often used. This drops the multiplier to ~5:1 or ~6:1 and 15,000/18,000 PSI respectively.

To flow the additional fuel at lower injection pressures, we need larger nozzles. However, larger nozzles negatively effect atomization, and part throttle use (raising EGT's while towing etc).

My question is, can you raise ICP to compensate for the loss of injection pressure to a point? And ergo use smaller nozzles to flow the same fuel within the given time constants?

More specifically:

What is the maximum allowable ICP?

What is the largest A code injector with a 7:1 multiplier?

What is the largest B code with a 6:1 multiplier?

Am I completely overstating the impacts/benefits of higher injection pressure?

Thanks!

 

Somewhere around 3400 psi ICP, the poppet valves will start to float. I think A codes go up to 200cc. If someone were able to build a 400cc split shot A code that could with stand 5000psi HPO and an IDM capable of sub-millisecond PW and an HPOP that could keep up, they'd be rich.

 

Wasn't swamps working on a HPFP set up for the 7.3?

 

Thank you. I'm guessing that's the poppet valve the solenoid controls? I haven't actually been inside one of these injectors, but that'd make perfect sense. The injector would no longer be controllable.

 

It seems to be stuck on the back burner. I'd love to see what it can do, but I don't think the cost will be feasible for the masses.

 

I couldn't resist. ICP sensors have been a common failure on our trucks of late. I have a strong suspicion that getting carried away with ICP and "Stinky Spikes" are shortening the life spans of many ICP sensors.


Feel free to blast away at me on this one - I've seen too much information to disregard my theory.

 

I'm not familiar with the ICP sensor specs, but it seems like a reasonable theory. I had a feeling the limit would be with sensors, injector o-rings, or the injectors themselves. I imagine the pump can be modified to produce higher pressure. Being the rails are cast/machined into the head, I imagine they can take whats thrown at them within reason.
Thanks again.

 

Seen a few oil analysis reports in 7.3L's running dual HPOP's & high ICP. The oil shears down much sooner, not a show stopper - just something to keep an eye on and be aware of.

 

Yeah, my very rudimentary understanding of oil shear, places it at a premium on our systems, as far as watching and maintaining oil change intervals. Common rail systems don't have near the same effect on the oil shear due to the fact that they don't use high pressure oil to drive the injector. They use high pressure fuel pump/lift pumps. I am not sure what the original thinking was, when the designers decided to use high pressure oil systems (HEUI), but they certainly weren't thinking of the hobbyist/enthusiast wanting MORE MORE MORE.