Nice update Idaho!
You have very good writing skills, magazine material, seriously!
Your turbo tuning and dialing in sounds similar to the encounters I had when getting my Powermax 6.0L turbo set up correctly. New reman injectors can do wonders for these older trucks and turbo performance.
Harry
Thanks for the compliment on my writing Harry, it's all done from my phone, and autocorrect and predictive text occasionally get the best of me, otherwise there wouldn't be the occasional oddity.
Let's talk about that turbo tuning. After I put the D66 on the truck, I installed a set of 37" tires. The truck cruises down the highway fine on the flat but hills the EGTs would creep up to 1250°F-1300°F, and that's a little high for a sustained pull up a grade. With more RPM came lower EGTs but try pulling a 6% grade with heavy truck traffic at 75mph and you'll feel my frustration. If the RPM is down around 1600, the truck wasn't making enough airflow from the turbocharger to keep the EGTs in check.
Initially I was playing with the engine tuning, and a little bit of timing change helped with the EGTs and the turbo spool up. But without doing anything too drastic, I was beginning to think it might be time to re-gear or go back to 35s. Then it occurred to me that it's not just an engine tuning issue, so I went back through my transmission tuning and completely reworked the shift schedule and converter lockup points to keep the rpm up in a more usable range. I haven't been able to recalibrate the speedometer and odometer to the new tire size yet, so I played around with the tune until I got it to the point where it holds first and second long enough even at light throttle that after the shift I'm above 1500rpm. At speed, the truck shifts from overdrive down to third (1:1) to kick up the rpm and avoid excessive heat build in the EGTs. The transmission tuning is helping a lot.
Now, I thought I had it figured out, at least well enough to get by. But, I'm never happy with "good enough" so right after the last oil change a couple weeks ago, I measured out a full dose of Archoil AR9100 and added it to the oil. It occurred to me that when I put I in my 6.0L, it improved turbo response, and since I haven't been running it for a while, it might be worth a shot again. Clearly it is magic turbo elixir, because the turbo lights about 100 rpm earlier, and EGTs dropped 50°F on average across the range. The truck also responded with an average improvement of 0.35mpg over 900 miles of daily abuse, so that's a perk too.
Finally, I'll share the oddest revelation in the EGT war to date. Last Friday I was working clearing out my storage and as I have frequently in the past, I had the key in the auxiliary position and the stereo on for a little music while I worked. Keep in mind, I've done this before and run the stereo for as much as five to six hours without issue. Well, to my unwanted surprise, the truck didn't want to start after about four hours. After making my first ever at call for roadside assistance in 26 years of driving, the tow truck driver hooked up, my truck started, and I was on my way. Fast forward to Monday morning and the truck had sat since Friday night's 100 mile drive home, I cycle the glow plugs, turn the key, and it cranks and fires, but it didn't sound "crisp" when cranking, it was just a little lazy. Monday afternoon was normal. Tuesday morning was a repeat of Monday's lazy crank, but Tuesday afternoon, the truck actually struggled to start at work. Pulled it into the shop, popped the negative cables off and load tested the batteries, and sure enough, the primary passed with flying colors, the secondary failed the load test. Where this story gets interesting is what happened after I put the new batteries in yesterday afternoon. I started home, and to my surprise the EGT's are down 50-100°F everywhere. The best I can figure would result in this is one of two things, 1.) the pyro readings are being skewed by the reference voltage not being in range for the design, or 2.) the bad battery may have been impacting the function of the PCM and IDM, the tuning doesn't have offsets for battery voltage that I recall, unlike gasoline engines where injector performance changes with voltage and there are tuning tables to adjust for those variations.
In the end, I'm really happy with everything about the truck except for the EGTs. That issue is probably going to require re-gearing the axles to resolve it. If I go that route, the next performance enhancement is going to be to upgrade the transmission, but I think I'm going to buck the system and not use the 4R100. I've been looking at swap possibilities, and while everything exists to be able to swap in an Allison 1000 5 or 6 speed, I've also recently discovered the info that there is a stand alone controller for a Mopar 68RFE, and that unit has, by far, the best ratio set in the pickup truck market. If it can handle 400 horsepower and 900 torque from a 6.7 Cummins, it should be able to handle my plans for this lowly old 7.3L including any power increases from injectors or more turbo, I doubt I'll ever exceed that power level.
So time for more research, and maybe an adult beverage to relax with this evening.
