Diesel cat or gas engine cat any difference?

[Hoss 350]

so our tailpipes might smell like pee or chicken pee since a ton of urea comes from chicken processing farms.

Yes, that is one of the places that I have heard discussed to get the urea if they do go with this system. However, the problem is that the EPA requires emissions systems to be fully self-controlled, meaning, they do not accept a system where the owner has to fill up a urea tank or else the system is rendered inoperable.

BTW, I can just see it now… all of the ways people come up with to save money on urea by “filling the tank” themselves, if you know what I mean…

NOx is one of those things that presents a real problem for diesel engineers, because it is created independently of the fuel burning, by heat alone. As we all know, more heat typically means a more efficient burn, and more efficiency means more power and better fuel economy. So, reducing the heat in order to reduce NOx usually means lower fuel economy, and less efficiency. Every other pollutant, across the board, is reduced with increased efficiency. The only way to reduce NOx without reducing efficiency (that I know of) that we have found to date is Urea injection. Every other option involves reductions in efficiency. Those options include EGR, lowering compression ratios, and so on.

So far, the EPA has done the following for the pollutants in our diesel engines. They have reduced compression ratios and added EGR’s for NOx, all of which reduced efficiency and created more particulate matter, hydrocarbon emissions and CO. They added a catalyst to take care of the HC and CO emissions, and are now adding particulate filters to take care of PM. All of this, unequivocally and without doubt, has reduced the efficiency of our diesel engines.

The route I wish they could have taken is to INCREASE efficiency across the board to get rid of particulate, HC, and CO, then injected urea to handle NOx. Net result is a very efficient diesel engine.

That is why you see early 90’s diesels getting 23 MPG and the current release of the 6 liter is lucky to get 15 (from what I’ve seen). They have reduced efficiency so much trying to reduce NOx that we are now burning MORE fuel, increasing our dependence on foreign oil, and just generally are getting screwed.

 

[DaveBen]

Hoss, your appology accepted, but you have made a small error. "so they are (from the factory) ALWAYS in a lean-burn situation," is not true statment. Diesels run from Rich to Very Rich. That is how they are throttled. They don't go lean unless you are coasting down a hill.

Dave

 

[Hoss 350]

Hoss, your appology accepted, but you have made a small error. "so they are (from the factory) ALWAYS in a lean-burn situation," is not true statment. Diesels run from Rich to Very Rich. That is how they are throttled. They don't go lean unless you are coasting down a hill.

Dave

Anytime a diesel burns rich, they puke black smoke, since there is not enough oxygen to fully burn the fuel. Since they do not have throttle plates, diesels are able to take in WAY more mass airflow than is needed to burn the amount of diesel injected at stochiometric. So, they almost always run lean.

Rich diesels are smoking diesels. Since most diesels do not smoke from the factory, then they come from the factory running "lean".

This is one of the reasons why we have yet to see direct injected gasoline engines, because the engine would not run at stocihimetric, and would therefore negate any operation of the NOx side of the catalyst. A DI gasoline engine would benefit greatly in efficiency due to the elimination of the throttle plate. Whenever you hear about "lean burn" technology as it relates to engines and efficiency, DI gasoline engines are probably at least part of wht they are talking about.

 

[powerboatr]

http://www.me.iastate.edu/biodiesel/Technical Papers/Wang Conclusion.pdf
read page one conclusions

sorry about the link but i have troulble doing the "poke here " stuff

 

[Hoss 350]

http://www.me.iastate.edu/biodiesel/Technical Papers/Wang Conclusion.pdf
read page one conclusions

sorry about the link but i have troulble doing the "poke here " stuff

Oh yeah, baby, NOW we're talking!

Unfortunately, this still does not fix the NOx problem (in fact, it makes it worse) which is the one that is causing efficiency issues. So, we still have a ways to go...