First off, I'll give a little background on what I've done prior to my injector installation. I installed a Fass 140 gph system on my 2000 Excursion with the 7.3 diesel. Next I installed an Adrenaline HPOP with all new braided stainless steel lines with the crossover line as well. Then I also installed the regulated fuel return from Riff Raff and have 55 psi at the fuel bowl with all fuel system mods. The old 7.3 (267000 miles) was running quieter than ever before! My intentions were to prep my entire injection system prior to my injector installation. The injectors that I installed were stock with 30% nozzles. Unbeknownst to me nor the supplier of the injectors, my engine was equipped with all AD injectors. I ended up getting 7 AD's and 1 AE. Now I have a pretty bad knock from the driver side bank.. My question to those knowledgeable with this engine is this combination causing my knock? Before anyone even suggests it, it's not due to any hydraulic condition during the installation. I made doubly certain that this did not happen by leaving the glow plugs out and turning over the engine before installing the glow plugs, plus, I turned the engine over with a long ratchet 2-3 times manually after the glow plugs were installed just to be certain. My gut feeling tells me that the AE injector is at fault. My reasoning is that this knock wasn't there prior to the new injectors plus the fact that the AE injector wasn't needed after my mods since there is adequate flow of oil and fuel to the injectors. I think my knock is due to preignition since the AE injector gives fuel quicker to the #8 cylinder which I don't need due to my mods. Am I correct or completely wrong? Please no speculation, just knowledge. Thanks in advance!

 

You should post this in the 7.3 section as well to get more looks, I have that adrenaline pump and 180/30 injectors but no regulated return and I'm still on the stock pump for now

 

The AE injector shouldn't "give fuel quicker to the #8 cylinder." The AE injector is also called a "Long Lead" injector, and "Long Lead" refers to longer lead time before injection. Longer lead time is slower to inject, not quicker.

The longer lead time was aimed to provide the injector in #8 a tiny bit more time to fill, because of a disturbance in the fuel rail caused by a pressure pulse from the interrupted injection of #6, which fires immediately before #8. As the pilot shot is sprayed into #6, the spray is momentarily interrupted, so as to spit up the shot of fuel.

The way that interruption is mechanically accomplished is to redirect the fuel inside the injector of #6 back to the fuel supply rail bored into the head, instead of into cylinder #6, for the length of time it takes the annular groove that redirects the fuel as it is being sprayed to pass the port where it is relieved into the rail, instead of being sprayed. It is an infinitesimally brief spit back, or hydraulic pulse. But it is enough of a pulse to disrupt the fill of #8.

So the thinking was, if #8 could be given a slightly longer lead time, as controlled by the location of the annular groove within the #8 injector, the hydraulic disturbance within the rail could be mitigated without mucking with much else. There was enough tolerance and variance in injector manufacturing that CAT found that it could cull a group of injectors on the high side of a given tolerance for location of the annular groove, in order for International to test this thinking to see if it would make a difference. It was found that it did, and thus the long lead time injector was born.

You have 30% nozzles. Assuming that means that your nozzles have bigger holes, and assuming you ordered these bigger holes in order to admit more fuel within the same number of milliseconds as a stock injector with regular size holes would, then one might say that your bigger hole injectors flow more.

I don't have higher flowing injectors, but I had to fill up a bucket of water today, and to do so quicker, I removed the spray thingy I had on the garden hose, because while the spray thingy was good at atomizing the water into a nice spray, due to constricting the orifice that the water had to shoot out of, not as much water flowed out of the hose with that smaller orifice, and I wanted to fill the bucket faster.

Which brings us back to your cylinder (the bucket) and the pilot shot of your split shot injector. Like me with my garden hose, you removed the constrictor on your nozzle tips by having them over bored.

Only a small amount of fuel is admitted to the cylinder during the pilot shot, and then the spray is stopped for a bit (when the spit back pulse into the rail happens, because the plunger is still moving, the fuel is just redirected away from the bucket).

Since you removed the constrictor, the first little bit of pilot fuel just drops in... just like that. High flow. Less restriction. Hence less atomization, and thus less molecular fuel dispersion, distribution, and link up with the oxygen molecules in the compressed air swirl, all of which lead to less likelihood of "preignition", as you earlier surmised.

If the pilot shot drips into the cylinder as a homogeneous droplet, it may not even burn completely until later. The entire point of the pilot shot is to get the air in the cylinder ignited hot and bothered so that the furnace is burning when the main shot of the fuel is sprayed in. If the furnace is already burning, it is more likely that the full value of the fuel sprayed in on the second shot will be burned efficiently during the power stroke.

More importantly toward your complaint, which was a knock, or a percussive injector noise, when the furnace is hot and burning, adding fuel is like pushing a stone that is already rolling. The second shot is adding fuel to an already burning fire, rather than starting a fire cold with an explosive bang.

So, it could be that with the bigger holes in your split shot injectors, your pilot shots are dribbled and inefficient. They may not pre heat the cylinder with as robust of a start in the fire for that power stroke. The main shot hits a warm cylinder, rather than a hot one, and then bang, critical mass, single shot, pre-millennial diesel clatter.

If you think that the noisy injector is #8, try swapping it with #2 temporarily. Or move it to the other side of the block temporarily.

Keep in mind that you changed several things at once.

1. You changed injectors.
2. You changed injector builders (from OEM to whoever rebuilt the injectors you bought)
3. You changed injector design (from OEM to 30% over bored nozzles)

You changed a lot of other stuff too, but since you said your engine ran quietly with the old injectors, even after changing all the other stuff, all that other stuff is ignored, because we are trying to find the reason for the new noise that you reported occurring after you changed the old injectors.

A huge unknown could be what is actually inside the rebuilt injectors you ordered.

Do you know for certain that you have split shot injectors?

You said you received 7 AD and 1 AE. Are you basing this description on the markings on the solenoids, or by what the injector rebuilder said, or both?

There is also an injection timing variable if you are running a tune. Does the tune play well with split shots that are 30% over?