Just filter your EGR

picosecond

Veteran Member
Joined
Apr 6, 2000
Location
New Milford, CT, USA
I've mentioned this before. Somebody please tell me if this makes sense. Can you do it?

With a cylinder filled with backward-pointing alternating-side baffles that forced the exhaust gas to sidewind through (something like I'd imagine the soot trap in the cat works). You could design it to break down for easy cleaning if you get a machine shop to make it right. Maybe fill it with stainless-steel wool for disposability, though it would be hard to ensure that no slivers went into the manifold.

Or how about the high-temp filter bags used in chemical processing and power generation? I didn't get much information from the websites: http://www.bgf.com/filtr.htm http://www.micro-filtration.com/home.htm http://www.king-filter.com/
 

Big Red

Veteran Member
Joined
May 22, 2000
Location
Newark, DE, USA
What are the requirements that would be placed on the filter?

How much airflow, how much particulate would need to be filtered and what max. temperature does the system see?

I don't know much about the system and don't have the time to dig into it, but if someone can guess at the above numbers I might be able to dig into filter types.
 
M

mickey

Guest
What you're talking about is a particulate trap. If you can invent one that works efficiently, reliably, and is relatively maintainance-free you'll be a millionaire overnight. This is one of the "holy grails" of modern diesel emission control research. Tons of money is being put into this.

Besides, reducing soot isn't the primary purpose of EGR. It's done to reduce NOx emissions, which you can't "filter" out. You can cut down on them a lot with a catalytic converter, but a good NOx cat isn't reliable in a diesel engine because the soot fouls them up. The catalytic converters in our TDIs are a very different design from the ones in the gas engines. They aren't very good at removing NOx from the exhaust. That's why VW has to retard the injection timing about 5 degrees beyond the optimum point, thus sacrificing a certain amount of power and fuel economy to keep NOx emissions legal.

The ultimate solution to these problems will require 3 steps:

1. Sulphur must be virtually eliminated from diesel fuel. This would cut down a lot on the amount of soot produced by diesels, thus allowing Step Two to happen:

2. Reliable Trap Oxidizers must be developed which can filter out and burn the remaining soot. No reliable production models are yet available. Mercedes Benz installed trap oxidizers on their diesels in the late '80s, with poor results. The required technology wasn't there yet, and the fuel was too dirty.

3. Once steps 1 and 2 are taken care of diesel manufacturers can install gasser-type catalytic converters to handle the NOx. If this all works well enough it might give them enough leeway to advance the timing back to where it belongs, thus giving us more power and fuel economy than ever! But none of these things will happen until the sulphur is out of the fuel. Support your local EPA!

-mickey
 

picosecond

Veteran Member
Joined
Apr 6, 2000
Location
New Milford, CT, USA
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by mickey:
What you're talking about is a particulate trap....This is one of the "holy grails" of modern diesel emission control research.

Besides, reducing soot isn't the primary purpose of EGR. It's done to reduce NOx emissions, which you can't "filter" out.
--mickey
<HR></BLOCKQUOTE>

Well, maybe it's not very green of me, and maybe I don't understand. But I don't really care about "filtering" NOx (gas separation is beside the point)... it's the particulates that coalesce into goo in my intake that I want to trap or filter.

The TDI intake manifold seems to be doing a pretty good job of trapping the crud on its own; maybe we could put just a little something in front of it, in the form of a 6" convoluted pathway to encourage the crud to settle down earlier. Something with quite a bit of surface area. Even better if there's disposable component, and it's easy to get to (a five minute, no tools job).

The NOx can do what it wants, unless taking the particulate out of the EG (or cooling it as a side effect) would defeat the emmisions purpose.

Matt
 
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