More 7.3 stuff.... The injector ramble...
Since the thread has gotten a bit quite, I thought I’d take a minute to address specifically the topic of fuel injectors. It took me a long amount of research, reading and learning to get my head wrapped around this topic, maybe I can ease your learning curve a touch. Fundamentally, there are a LOT of different options and opinions out there, so it can be difficult to weed through it all, and it’s a very big ticket item, both in terms of money and the benefits and pitfalls.
First off, some very basics. The system used in the 7.3 is called an HEUI, which stands for Hydraulic Electric Unit Injector. The best analogy I’ve found for understanding this is to think of the fuel injector as a turkey baster. The baster fills with fuel from the fuel rails (cast into the heads), then the main computer tells the Injector Driver Module (IDM) to fire the solenoid on the injector which then allows hydraulic pressure to essentially squeeze the bulb of the turkey baster and fire the fuel into the cylinder. The hydraulic pressure is provided by a separate High Pressure Oil Pump (HPOP). The oil pressure provided (through again, rails cast into the cylinder head and high pressure lines from the pump to the rails) by the HPOP is regulated by the Injector Pressure Regulator (IPR) and monitored by the Injector Pressure Sensor (IPS).
The IDM provides the high current voltage to fire the injector solenoids, while the main computer controls the parameters that the injectors are fired with. These include Timing (when they are fired), Pulse Width (how long they are fired) and HPOP Pressure (how much oil pressure is used to “squeeze” the injector). The only feedback this system provides back to the computer is the HPOP Duty Cycle, which is a percentage of how much capacity is utilized from the HPOP to maintain the computers specified Pulse Width, Duty Cycle and Oil Pressure.
Obviously, the higher and longer you fire the injectors, the more work the HPOP has to do, so the Duty Cycle becomes one of the principle numbers for understanding the overall health of your injector system and efficiency. If I remember correctly, you’ll get a temporary check engine light if your Duty Cycle exceeds about 65%, though I believe some tuners manage to turn this off.
Fuel injectors in the 7.3 tend to last about 200,000 miles before they begin exhibiting symptoms that effect the performance, efficiency and function of the system. This is principally due to wear of the poppet valves within the oil side of the fuel injector. The injector fires by closing these poppet valves, which causes the oil pressure to build (at up to and over 3000psi in some cases) and fire the fuel into the cylinder. Subjected to millions of high pressure oil cycles, the poppet valves gradually wear and have trouble fully closing, this is most evident by requiring an ever increasing Duty Cycle to maintain required pressure from the HPOP. This also becomes evident by harder starting, particularly when cold, grey smoke with unburnt fuel on cold starts, reduction in power (particularly when cold…) and in extreme cases the motor can start cold, but will then die after it warms up.
Personally, I ran my truck to about 260,000 miles before I replaced my injectors, but many of these symptoms were readily evident when I acquired the truck at about 210,000 miles. It was tough to start cold, pretty gutless until my oil temp got over 90 degrees, and put out a pretty significant amount of grey diesel-smelling smoke. As you can imagine, spouses, neighbors and anybody parked near you at the ski resort is not generally thrilled with this sort of thing. I wasn’t thrilled with the power reduction and the CEL going off as I regularly pegged that Duty Cycle.
So… in a nutshell, if you own a 7.3 and are near or over that 200,000 mile mark, it’s worth beginning to get your head and finances wrapped around the whole injector thing.
The downside here is that you can probably plan on blowing a whole Saturday swapping the injectors out (though it’s not a bad job, it’s a lot steps and time laying on top of the motor), and then obviously the financial ramifications. Though you could spend less, the wise thing to do is probably prepare yourself for spending between $2,000 and $3,000 even if you’re not necessarily looking to build some kind of horsepower monster.
Now the upside to this is that after you replace your injectors your motor is going to basically run like new, furthermore, you have a golden opportunity to make your motor run far far better than it ever did when it was new. As International/Navistar basically stopped developing this stuff in about 1998, then Ford went ahead and made it worse, the aftermarket industry has soldiered on and now provides us with fuel injectors vastly superior to what your motor came with.
Let’s take a brief moment to discuss what Ford did to us. I think it makes sense to everybody that for maximum power and efficiency we should pick the right moment and inject our fuel in one burst. Ford on the other hand was worried about peoples complaints about “injector clatter”, so they came up with the idea of a “split-shot” injector, used in almost all 7.3’s (some rare early exceptions) what they did was setup the injector to provide a brief pre-shot right before the main shot of fuel. What they hoped this was would do is quite the clatter, but it didn’t really do much. What this did do was put an excess load on the HPOP, cool the cylinder, sometimes compromise fuel pressure and unnecessarily increase the time length of the injection event. Essentially… a split shot injector sacrifices performance and reliability for an almost imperceptible difference in engine noise reduction. I would absolutely NOT recommend under any circumstances that a reasonable adult replace the fuel injectors in a 7.3 with new or remanufactured units from Ford or International/Navistar.
The aftermarket industry has left the OEM’s in the dust. Aftermarket fuel injectors are almost entirely “single shot” type, even in stock sizing this will result in an instant increase in fuel millage and power and a reduction in HPOP duty cycle.
As a side note, HPOPs rarely fail, HPOP problems are almost always actually worn injector problems, and a new set of single shot injectors will typically find even an old HPOP (and even an older e99 or OBS HPOP) all the sudden working better than new.
Furthermore, the aftermarket industry has devised what’s referred to as a “Hybrid” injector. By hybridizing parts available from Ford and International/Navistar’s industrial offerings these aftermarket injectors have different plunger ratios and are able to drive a higher pressure injection event while utilizing even LESS HPOP Duty Cycle. These are not as applicable to the ultra-high power drag racing and truck pulling crowds, but for moderate power applications it’s a major benefit. Higher pressure injection event, shorter pulse width, lower Duty Cycle. Of course, the only REAL downside is that they cost more.
So with all that, understanding moderate goals of replacing old injectors with something more reliable, that won’t require a lot of supporting modifications, a properly sized set of Hybrid, Single-Shot injectors is pretty much a no-brainer and will realize a significant a enhancement in performance across the board, including fuel millage, power and reduced demand from the HPOP.
To understand injector sizing, these are usually indicated by an AAA/BB arrangement where AAA is the injectors’ fuel delivery capacity and BB describes the nozzle size. Nozzle size is typically described as “Stock” or as “146”, where I believe 146 is the part number of the stock nozzle. Larger than stock nozzles are described as a percentage of orifice size increase over stock, typically 30%, 80%, 100%, 200% or even 400% for extreme cases. Stock injectors used in most PSD’s from 1999-2003 are “AD” code, this is a split shot injector in size 140/146, so it’s an injector with 140cc of fuel delivery capability and a stock nozzle. As another example, I’m currently running 250/200 Hybrids, so this is a Hybrid, Single-Shot injector with 250cc’s of fuel delivery capability and a nozzle that’s been modified with a fuel orifice 200% larger than the stock 146 nozzle.
In general most of this is pretty obvious, more CC’s of fuel means more ultimate power capability, larger nozzles help deliver more fuel quicker, so more fuel is delivered over a shorter pulse width. The principle problem we have to balance with this is that injector size increases, it requires more demand (duty cycle) from the HPOP to successfully empty the injector. It’s just impossible to empty a huge 400/200 injector with a stock HPOP, it can even be troublesome with a moderately sized 160/30 injector. This is where the magic of going with a Hybrid injector comes in, since the hybrids have a different plunger ratio and require less HPOP duty cycle, a moderately sized 200/30 Hybrid Single-Shot is easily handled by the stock HPOP, and even the slightly weaker HPOP provided in early 99 motors. (as an aside, I’m running an upgraded Adrenaline HPOP)
Sizing injectors with input over the internet can be a little difficult, if you go hop into the Powerstroke Army forums you’re going to get some pretty wacky answers, along the lines of “I love my 400/200 injectors! You just have to do some supporting mods!”, Never mind that some of those supporting mods might include huge turbo’s, block fill, dual fuel pumps and valve spring upgrades.
Assuming in this thread that we aren’t interested in turning this into a massive engine project, but instead just want good running motor with a realistic power upgrade my top level recommendation would be a set of 200/30 Hybrid Single-Shot injectors from Swamps Diesel Performance. This injector will start, run and head on down the road just like a stock setup (well, better actually). In a modest tow tune you’ll be making more than 300hp, with less HPOP duty cycle than stock, and excellent atomization with no smoke and very low EGT’s. In a hot street tune (that you could run all the time if you want) you’ll make close to 400hp, and again, it will run like a stock truck, but with a whole lot more pedal. Full out tune could yield close to 450hp, but it might be kinda smokey off the line (less so at low altitude). Even at this power level your still looking at stock levels of reliability and only mods I’ve mentioned before (intake, exhaust, minor turbo) are really recommend. To quote Dave from Swamps “totally fine on a stock motor as long as you only beat the snot out of it occasionally”. To clarify… by occasionally I think he means only like once or twice a day, assuming it’s a daily driver. He does recommend that you monitor fuel pressure if you doing extended full-throttle runs in the max setting (like drag racing), as you’re getting close to the max fuel pump capacity and running out of fuel pressure can damage the nozzles (cooled and lubed by fuel). But assuming you’re NOT going drag racing, this is not really a concern. Running these injectors in a hot street or tow tune you could mash the throttle to the floor and shoot up and over Vail Pass at 90mph without a concern in the world (other than the highway patrol and that Prius in the left lane).
Now the downside… These puppies cost $2,225.00 and have a $1,000 core charge, and REQUIRE custom tuning. Though you already have a Hydra, so Swamps will send you 6 custom tunes for free via email and won’t hit you for a core charge if you return your cores within 30 days.
At this point, it’s worth clarifying that cost is the only REAL reason to not go with the hybrid injector. You’re going to all the trouble of swapping them out, so other than missing the money, you might as well take the upgrade. If you don’t need the extra power, you can always just click the hydra down a notch, all the way to stock power if you want.
If your dead set on saving some money, another popular option is the 175/146 injector. This is a single-shot, but not a hybrid. You get a lot more fuel capacity and the stock size nozzle helps keep the HPOP duty cycle reasonable, but I still wouldn’t call them cheap at $1,875.00. You still must have custom tunes (all single shot injectors will require custom tunes), but they are again included for free. These injectors are still capable of bumping up a 7.3 to over 300hp and can be ran on a totally stock motor. These are really popular with guys who almost exclusively use their trucks for heavy hauling, and I have several friends who are very happy with them.
Lots of companies out there make fuel injectors for these trucks, personally when I’m looking at spending this kind of money, Swamps Diesel is the only company I’ll even remotely consider. They make the best fuel injectors in the business, have a sterling reputation and excellent customer service. They do a great job with the custom tuning and are more than happy to correspond via email and customize tunes as necessary. I highly suggest browsing through the website and reading some of the stuff. Dave also has a really nice injector troubleshooting document and installation instructions. You’ll notice that the regulated return fuel system is recommended by Swamps with most injectors, you can definitely run the injectors I recommended without doing this upgrade, though it’s a really good upgrade for a lot of reasons and is thus included as sort of a blanket recommendation.
Okay, wow. That was a lot of typing! Did I miss anything lol?
Crap… I did. Its also worth figuring it if you have a motor with Forged rods or with PMR rods. Google is your friend on this topic, you should be able to find info based on year, VIN or removing an inspection port on the block and using a borescope to inspect the rods. If your forged, go party! If you have PMR rods you’ll want your tuning to cap your power, probably around 380hp, and maybe limit your cyclinder pressure at lower RPM’s. Again, this is where I’ll STRESS that you have good custom tunes. Good tuning means the slightly weaker rods are a non-issue at appropriate power levels. More than a couple of people have been disappointed by poor tuning and the sudden appearance of a PMR rod into daylight.
