Here it is; a working theory on tuning woes when swapping stale sticks for the economical equine enhancers... remanufactured injectors. For those unfamiliar with me, I am not an expert, a diesel mechanic, or a long-term diesel owner. I ask a lot of questions, do my mods, and measure the results to the level that "****" doesn't cover.

New injectors have a crisper response to the High Pressure Oil than used ones do, hence... we replace the old ones. When we choose to save a few bucks and go reman, each rebuilder has their own procedure and policy for the level of the rebuild and just as important - the level of bench-testing.

Let's say a rebuilder automatically replaces all internals, but that doesn't mean the core they put the internals in is up to snuff... so the rebuilder bench-tests the injector, while monitoring flow. After the bench-test, a good rebuilder will match up a set of 8 injectors with near-identical flow and record that data for future reference.

How is the bench-test done? That right there is the "core" of many a woe once it reaches the head of a 7.3L: Rebuilder A does a flow test at X pressure, with Y pulsewidth, with a "test fluid" at Z temperature. Rebuilder B does a flow test at Y pressure, with Z pulsewidth, at X temperature. Rebuilder C does a flow test at both settings to make sure the injectors match up across a broader spectrum of operation. Throwing a number at this to get a better understanding, let's say rebuilder A tests the injector at 700 PSI, with a pulsewidth of 1.5 ms, and the test fluid is 100 degrees F. This tells us the injectors are matched at a cold/cool startup, but it tells us nothing about what will happen when the engine temp is full and the ICP drops to a warm idle of about 500 PSI. Take Rebuilder C who does a bench test with the same settings, but also does a test with the pressure at 500 PSI. That rebuilder is more likely to know what would happen when the engine warms up and drops ICP, as well as what will likely happen when the ICP climbs as the end-user communicates to a ricer by way of smoke signals. OK... that's one aspect of how choosing your rebuilder for reamans can make a difference once the IC pipes are torqued back down.

Now the tuner: Your tuner gets flow data from the rebuilder... as well as a request from the end-user (that's you and I, by the way) for a quieter idle, a subtler throttle, and better road manners with Cruise Control. OK... that means keep the ICP low on those remanned oversized injectors the end-user ordered up for a daily serving of puffed ricer. Wait... rebuilder A tested at 700 PSI and there's no clue as to what would happen if the tuner drops to 500 PSI to fill the "special order" of the end-user. Guess what... 1, 2, or even 3 injectors flow differently than the others at the reduced pressure and the Perdel on each leaves speed bumps in your idle (imbalance or "lope"). The fix? Set the idle parameters to match the rebuilder's test parameters and you will have one smooth idle... at the expense of noise level, throttle sensitivity, and Cruise Control stability.

If you are shopping for injectors - go new or go researching... and accept the fact that this still doesn't gaurantee instant success, but it reduces the odds of a truck collecting dust and disgust instead of miles and smiles.

This is the point where others more knowledgeable than I fill in some gaps and assist me with my errors. Next!

 

My injectors were rebuilt and stuffed with all new parts. My builder said that a few of my injectors needed minor machining before the parts went in.
I didn't ask what/when/where, but it makes me feel good knowing that he just didnt shove in new parts and call em done.

 

Heck I am simply popping popcorn and settling in.

 

Because of your story Tugly, is why I have decided to go with Swamps. Tomorrow I'm going to have another long talk with David and then place my order. I have decided to go with Swamps for injectors and tuning. I most likely will go with his recommendations. They have done lots of dyno and cylinder pressure testing on their injectors with their tuning. It seems like he knows his stuff. Matched tuning AND injectors is what I want, and Swamps says they can provide it. Their warranty is the best I have found. One of my questions I will ask him tomorrow is, exactly how they test the injectors before they get shipped out. I too want to know how thorough they test their injectors. I sure hope I have better luck than you had.

 

I'm almost out of the tunnel, I can feel the heat of the reflecting sun as I near the exit. I have one injector slightly out of balance at idle and the fantastic customer support I've been getting spackles the furrows on my brow. One more open VC on the driver side and I shrink-wrap the Buck$Zooka for the winter.

Injector and tuner from the same vendor can be pointless... as in... no finger-pointing.

In all fairness, my biggest issue was a couple of injector bolts that worked loose during my vacation... and that plucked the nerves more than anything else.

 

Injector and tuner from the same vendor can be pointless... as in... no finger-pointing.
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That's what I'm looking for.