Double Catalytic converter requirements?

[msmnick]

So, hey all. I've been working on an idea recently to try and "clean up" a volkswagen TDI for a nut friend of mind. I also had the idea to use this technique to help improve emissions on some of the fleet which may have issues next time around for CA emissions, as I plan on moving back and going to school their.

I know certain vehicles, particularly the 4.6l mustangs come to mind, run two cataltyic converters in-line in the exhaust system.

However, when running an aftermarket cat, would you be able to put to catalytic converters intended for primary use inline, and would this be a positive or negative effect type of thing? That is, would the second one improve the situation or would it suffer potential failure due to its location, or not being able to get up to temp, etc?

Perhaps there is availability of a secondary post-cat that I am not aware of, but I'm curious Nonetheless.

I'd also be interested in hearing your thoughts on this, I realize that this will likely bring down efficiency overall because of the extra restriction. One way I was hoping to combat this was with a good High-efficency High-cell count Metal core unit as at least the primary, and perhaps as the secondary as well. I'm sure the comparison of these to OE cats as far as emission reduction is debatable, but I have used Pace-setter metalcores in the Audi and passed emissions with them, so they are passable at least.

Ok, thanks for reading, Lets see what the ideas would be. (note, the diesel is not required to pass emissions, but she wants less soot out the tail-pipe, so to speak. A diesel injection pump upgrade is on the table as well)

[shovel]

Starting mid-year in 2000, v6 equipped S10's began to get dual inline catalytic converters... the rear one stayed in the same location and is the same part number, but a new smaller one was added a couple feet forward, immediately after the junction of the two cylinder banks' exhaust.
This "precat" as it's called serves only one purpose: it heats up more quickly due to being closer to the engine and made of a lighter material - so it reduces HC emissions during the first few minutes of driving before the main cat gets up to temp.

"a guy I know" shattered the catalyst inside his precat after partially crushing the enclosure with a rock on a particularly rough Arizona road, removed it entirely & blew out the main cat with a leaf blower (to remove debris from the damaged precat) and filled the gap with a section of straight pipe. No driveability difference was apparent, the ECU did not report a post-cat O2 sensor failure, and the vehicle produced nearly identical #'s on its next emissions test.

YMMV.

[ncs]

2 cats? Weak. 2.0l turbo Subarus come with three cats, one in the uppipe, one in the downpipe, and one in the midpipe. Don't diesils need a different type of cat than gas engines?

[msmnick]

Originally Posted by ncs

2 cats? Weak. 2.0l turbo Subarus come with three cats, one in the uppipe, one in the downpipe, and one in the midpipe. Don't diesils need a different type of cat than gas engines?

Yes, diesels require specific cats for their application. Still, they are available and the theory behind them is the same.

I typically use Jegs' online catalog to get high-performance type cats. I think they've got diesel ones as well.

[RobertSmalls]

Originally Posted by ncs

2 cats? Weak. 2.0l turbo Subarus come with three cats, one in the uppipe, one in the downpipe, and one in the midpipe. Don't diesils need a different type of cat than gas engines?

Yeah, and the 1996 Subaru 2.2L, Cali emissions, has a $800 cat assy. That's Insight-cat money, and the Subaru can't even do lean burn.

Universal 49-state aftermarket cats ftw.

But sorry, I don't know much about diesel cats.

[msmnick]

Originally Posted by RobertSmalls

Yeah, and the 1996 Subaru 2.2L, Cali emissions, has a $800 cat assy. That's Insight-cat money, and the Subaru can't even do lean burn.

Universal 49-state aftermarket cats ftw.

But sorry, I don't know much about diesel cats.

Hmm. So I wonder if running two inline would do much then. Maybe I'd be better off with an aftermarket ecu and wideband and just tune the thing to be efficient as hell... Though, I don't know how I feel about that on diesel/Turbo. Also, if you give a diesel LESS fuel, you get more soot out the back, go figure...

[bgd73]

stick to singularities.
you may want to check out trucks with particulate filters, and make a mini version.

[mwebb]

..."I'd also be interested in hearing your thoughts on this, I realize that this will likely bring down efficiency overall because of the extra restriction. One way I was hoping to combat this was with a good High-efficency High-cell count Metal core unit as at least the primary, and perhaps as the secondary as well. I'm sure the comparison of these to OE cats as far as emission reduction is debatable, but I have used Pace-setter metalcores in the Audi and passed emissions with them, so they are passable at least.

Ok, thanks for reading, Lets see what the ideas would be. (note, the diesel is not required to pass emissions, but she wants less soot out the tail-pipe, so to speak. A diesel injection pump upgrade is on the table as well)
"...
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if a VW TDi has a lot of "soot" visible in the exhaust
there is a problem in the system
locate and repair the problem

do not think that by self engineering a "cat" to the car , you are going to improve something or solve anything .

have a look in VWvortex forum