This may not garner much play, but I'd love to hear some responses/insight regarding catalytic converter placement on an upcoming full exhaust swap for my v8 dakota. yeah yeah I know it's 'technically not worth it', but I'm the biggest fool in the world for exhaust systems, so this is my 'thang'. The scoop: Edelbrock shorty headers, modified crossover merge with a flowmaster y-pipe (y214300), run single into a 3.5" donaldson muffler I scored for cheap on ebay (probably subdued exhaust tone), then 3" single tail-pipe with a sweet dual exhaust tip I fabricated a while back with a proper 3" to 2.5" split. Now to the dilemma-


Would parallel 2.25" cat converters before the y-merge affect any 'benefit' gained by having a well designed merge?

To me, the benefit of twice as much cross-sectional converter area seems to be the best way to go, although packaging isnt as efficient (not a concern, really). It just seems that if I'm going to the trouble of adding headers/updated y-pipe/better muffler, then why not optimize converter setup as well.

10/7/2011 8:40:09 AM

Are the converters ceramic or metallic substrate?

10/7/2011 8:52:51 AM

It's undecided currently, as I've eyeballed both

What is hard to swallow is that the cross-sectional area varies wildly across the models, and in many cases the 2.25" units have basically the same area as a 3"


And by well designed merge I was referring to the converters possibly damping the pulse/scavenging effects of the merge

[Edited on October 7, 2011 at 9:25 AM. Reason : or am I full of shit]

10/7/2011 9:20:07 AM

well, i think its safe to say you are full of shit. now whether that applies to this mufflery mess i have no idea.

10/7/2011 9:44:18 AM

^i figured you were tired of listening to me ponder via gchat (and quit shitting up my thread arghx might not want to post&ponder if you keep it up )

10/7/2011 10:20:38 AM

There's a lot more to a converter than its cross-sectional area such as frontal area, cell density.



Metallic substrates cats tend to have to a greater frontal area and a different cell arrangement compared to a ceramic cat of the same nominal dimensions.

Quote :

"And by well designed merge I was referring to the converters possibly damping the pulse/scavenging effects of the merge"

I doubt any of us have the resources to say this with certainty. It would take a lot of trial-and-error chassis dyno time, expensive modeling software, or instrumentation that none of us could afford. I will say that based on what I have read, the cats are going to create a laminar flow as the exhaust enters the converter. I imagine that dampens pulsation effects at least to some extent, but pulsation effects are going to depend on operating conditions anyway.

10/7/2011 10:24:52 AM

^aha, that's what I'm after!


I'll read that data you're sending and ponder some moar. Even so, it appeareth that once I select a converter, that running two in parallel would be the best bet (appears that the metallic-cats have similar case dimensions across many tubing sizes)

[Edited on October 7, 2011 at 10:42 AM. Reason : -]

10/7/2011 10:37:46 AM

....so what's up with the 25% price increase on Magnaflow's spun-metallic converters? Did i miss a general price increase or what?

11/30/2011 1:15:36 PM

Cats, who needs cats?

11/30/2011 1:21:42 PM

situational :BEATUP:


but you know, stock truck, it's cheaper to do run cats than to try to beat them.

11/30/2011 1:32:19 PM

yes... sometimes...

11/30/2011 2:07:09 PM

clarity: stock OBDII truck

11/30/2011 2:40:37 PM

sometimes a resistor is as good as a cat.


Hey, so you know the whole readout they get,

they all comes from 1 02 sensor right??

how does 1 voltage give them that much info?

11/30/2011 3:56:04 PM

I failed with an OBD1 car during the visual inspection of the cat.

11/30/2011 7:31:31 PM

^ Lol.

Jiffy lube gave me hell about my 944 wanting to do an emissions test on an OBD1 car, so I took it across the street to Meineke. They did a quick visual for the cat and passed it. They completely igorned the huge crack in the headers

11/30/2011 7:36:42 PM