Your ideal emissions setup?

As most of you know it's illegal to remove or disable emissions control devices. But if you could legally delete some of these things from your engine, which one of these items:

• EGR (Exhaust Gas Recirculation)
  
• DOC (Diesel Oxidation Catalyst)
• DPF (Diesel Particulate Filter)
  
• SCR (Selective Catalytic Reduction, a.k.a. the DEF system)

would you remove? Or if you have already done some deletes, which ones did you remove? Note that I am not saying I would do a delete if I owned a Diesel, but I'm just wondering.

In my opinion the ideal setup would be aa DOC and an SCR system, no EGR or DPF.

 

Because I feel it's necessary to strike a balance between reducing emissions and maintaining efficiency, and I hate some of these items more than others. Some deletes I get, some I don't.

With an EGR system you're dumping exhaust gases back into the intake. As you may know, there's a lot of soot in the exhaust on a Diesel engine that is getting plugged up in your EGR cooler and intake. Not only that, EGR reduces the efficiency of your engine as there's less oxygen in the cylinders and combustion temperatures are also lower.

Modern DPF systems will have a regeneration system which pours fuel into the exhaust, adds air, and lights the fuel on fire to increase the DPF's temperature and clean it out. Does burning more fuel to save the environment make any sense? I didn't think so. Not only that, the EGR system also reduces your combustion efficiency which means less power, higher fuel consumption, and more soot being produced. And now your DPF plugs faster.

A DOC is like a catalytic converter on a car, and its job is to cook any unburned hydrocarbons (so unburned and incompletely-burned fuel and oil vapours) into water and CO2, as well as some of the soot (carbon) into CO2. It also helps reduce NOx slightly.

The SCR system injects urea into the exhaust, which decomposes into ammonia at high temperatures. Urea and ammonia react with NO, NO2, and other nitrogen oxides to form nitrogen and water.

Lastly, Diesel engines are much more efficient when they run lean than when they run rich. The excess of air allows you to achieve a very thorough burn, so you produce a lot less soot (black smoke). This does increase NOx, though (since you have lots of nitrogen, lots of excess oxygen, and lots of heat), but the SCR takes care of that without interfering with the combustion process.

In my opinion, EGR really should have been only a temporary fix until SCR systems took over.

 

...and is capable of running without any electrical input.

 

DPF's also present another problem as it affects what fuels you can run on. A big advantage of Diesel engines is that they'll run on pretty much anything, and a lot of guys run waste cooking oil and waste motor oil in their Diesel (pickup) trucks. If I owned a semi I would also be interested in running my waste fluids (not coolant, obviously) in the fuel tank. Why is this a problem in a Regen engine? Because in a Regen engine, the same fuel that the engine runs off of is used to provide heat for cleaning out the DPF. I'm not sure about this, but my first impression is that waste motor oil (since it's loaded with black carbon) would burn very inefficiently in the exhaust stream and would take a much longer time to do a regen since it would produce soot as it burned.

Going off on a tangent here, but I personally feel like the whole fossil fuel phase-out is almost completely hype at this point. Our oil and coal reserves are still more than plentiful enough, and our efforts should not be on phasing them out at this point, but instead they should be focused on emissions control (specifically aftertreatment). The reason I'm saying this is because I'm very interested in biofuels and the use of pyrolysis to turn waste (garbage, sewage, sewage sludge, yard waste, and all kinds of things) into oil, which can then be refined into biogasoline and biodiesel. But that's for another time.

By taking out the DPF you don't have to worry as much.