You guys brought up a sore subject. My experience is that displacement was increased to offset intake and exhaust load as well as parasitic drains such as high pressure pumps. Tier II was about as good as it gets. We had compression still, electronic fuel injection HPCR had just been introduced. The big 3 had their big bores putting millions of miles on American roads. DD series60 , the Cat 3406E and my favorite Cummins N14 Celect. I-H had the HEUIs for mid range. At the time ICP was maybe 2200-2500 psi. The manufacturers had reduced PM very low, but the goal post was moved. Now it had to be reduced further , oh and reduce NOx too. So now we're into EGRs and some DOCs for on highway. ( garbage trucks burning to the ground, remember that? )
That was short term. Particle traps are the next step, oh, while you're at it, reduce the noise from the inlet as well. Introduce panel filters and all those strange air cleaner designs. Now we have EGR and reduced flow capacity coming and going. Just to reduce NOx they knocked the compression ratios way down and introduced "cooled EGR" This reduced ignition efficiency so now the DPF is working hard trapping all that soot. Soot is being suspended in the oil and zinc is gone. Now we need to regenerate the DPF, some have burners to achieve heat, others use a 7th injector and others run in cylinder post injection. It doesn't matter which boondoggle it is, it's wasted fuel. Fuel used for something other than work. Now they realize that emissions require heat to work properly. You can't reduce soot to ash at idle. Now we get our compression back, fuel pressure goes sky high, fuel filtration becomes the biggest challenge. 5 micron final pass filters are now common, injector longevity is out the door. Higher heat , higher compression shows that current metallurgy is insufficient. Blocks show erosion, heads dance on the deck. EGR coolers are failing regularly. Coolant additives packages are pushed to their limits. Exhaust temps in manifold are nearing 650°F under load without dosing fuel for after treatment. Thermostat opening temps are climbing higher. 195° t-stat are common. So now combustion efficiency is up, we've got compression, temperature and metallurgy is creeping up. NOx is still too high, now we gotta add DEF to the exhaust steam to make sunshine and rainbows. Here's the plus of DEF injection. Some machines can forego EGR, not have it and address NOx strictly in the tailpipe.
The horsepower draw was really evident to anyone who performed a delete or perfmed a conversion in 3rd world countries. An A40D haul truck had a 13 liter engine, in the subsequent generations of emissions F & G they had to up displacement to 16. To be clear, a D13C is no slouch. Last I heard, they're running D16H engines. Through Ritchie bros, 3rd world countries could buy American used equipment, get a voucher so that once received at the dock, the dealer would remove all emissions equipment and reflash the computers. They get all the power and efficiency of a modern diesel without the emissions hassle.
I have watched over the last 20 years as this BS has crushed Mom n Pop outfits who didn't have the resources to survive the first breakdown post warranty. A machine that's otherwise fully functioning, derating, creeping at idle because a thousand dollar sensor decides it wants to be out of range. All dictated by foreign treaty and enforced by the EPA. Phooey
