Maximum ICP and Injection Pressure
Thread Starter
|
Junior User
Joined: Mar 2008
Posts: 81
Likes: 0
Maximum ICP and Injection Pressure
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!
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!
Laughing Gas
Joined: Nov 2013
Posts: 868
Likes: 1
From: SoCal
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.
Thread Starter
|
Junior User
Joined: Mar 2008
Posts: 81
Likes: 0
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.
Laughing Gas
Joined: Nov 2013
Posts: 868
Likes: 1
From: SoCal
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.
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
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.
Feel free to blast away at me on this one - I've seen too much information to disregard my theory.
Thread Starter
|
Junior User
Joined: Mar 2008
Posts: 81
Likes: 0
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.
Thanks again.
Trending Topics
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
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.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Lead Driver
Joined: Jun 2007
Posts: 7,760
Likes: 27
From: Hampton, Maryland.
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.
Thread
Thread Starter
Forum
Replies
Last Post
88 Ford IDI
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
20
Feb 17, 2016 06:31 PM
snubber
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
13
Dec 2, 2004 07:38 AM