Boomhauer, what does the tier 4 emissions do to earn your ire?
Oh where to begin...
There are several emissions control systems in use for Tier 4. You have diesel particulate filters, urea injection systems, and exhaust gas recirculation systems
These systems have lots of electronics to manage the emissions systems. I don't have anything against electronic engine controls in general but there is a point where the amount gets rediculous- and every sensor is a potential point of failure.
Then the various systems themselves have issues. DPF filters have to be "regenerated" or cooked out by the engine running at high loads periodically. The process can take a lot of time and use a lot of fuel. We recommend to owners that they run the engine with a load on and at higher RPMs frequently to try to keep the filter in good shape, mostly low RPM usage and not doing the regen cycles will mean a clogged filter. We have a special oven that the filter can be baked in to get it cleaner (think of like how a self-cleaning oven works) Basically the DPF system is a pain in the ass.
The EGR systems send the exhaust gases back into the cylinder to try to reduce emissions by displacing some of the incoming fresh air. This causes some issues, and diesel owners who have removed EGR systems have noticed a marked improvement in reliability, but it does void the warrenty.
Basically, this:
By feeding the lower oxygen exhaust gas into the intake, diesel EGR systems lower combustion temperature, reducing emissions of NOx. This makes combustion less efficient, compromising economy and power. The normally "dry" intake system of a diesel engine is now subject to fouling from soot, unburned fuel and oil in the EGR bleed, which has little effect on airflow, however, when combined with oil vapor from a PCV system, can cause buildup of sticky tar in the intake manifold and valves. It can also cause problems with components such as swirl flaps, where fitted. Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of diesel particulate filters.[9] EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity.[10]
The urea injection systems (diesel exhaust fluid) is the least problematic by far- all it does is inject the solution into the exhaust stream. It's simply an extra expense. The DPFs and EGRs are what cause the most trouble. I would look to avoid them while you can still get older equipment in good shape.
Modern diesels are great engines- lots of power and very advanced. The issues with modern diesels come mostly from the emissions systems, which also reduce fuel efficiency in many cases. Until the emissions systems issues are more advanced, I'm not a fan of them- except for the job security...we are getting some of the issues resolved (when the first tier 4 stuff came out it was an absolute nightmare) so do your research on the new stuff before committing to buy- some makers are having more trouble than others.
