Exhaust noise and catalytic

greiswig · **Posted:** Mon Jan 09, 2006 2:00 am

With all this talk about muffler upgrades boosting performance without much effect on the noise level, I'm wondering what a better flow catalytic converter would do, too? Or is the converter acting as a muffler as much as the muffler is?

fireman1028 · **Posted:** Mon Jan 09, 2006 10:33 am

The reason there isn't a difference of sound is because of the turbo. It acts like a muffler itself. The main reason we are changing the exhaust is for flow. The stock muffler is the same muffler that is used on all Liberty's (restrictive). Our engines need a more free flowing exhaust. I am not really sure about the cat, maybe some others can chime in a little more.
Allen

greiswig · **Posted:** Mon Jan 09, 2006 2:15 pm

Okay, here's a different way of asking the question: suppose that, in replacing the muffler with a straight-through design muffler, one were to find that a 2.5" hole in the catalyst matrix had mysteriously appeared, making it a straight-through design catalytic converter. I wonder what effect that would have on the exhaust note?

LibertyCRD · **Posted:** Mon Jan 09, 2006 2:48 pm

With the straight-pipe and the cat on the CRD Jeep sounds like a small to medium sized farm tractor. My guess is that with no cat it would sound the same, only louder. Not a very pleasant exhaust note at all if you are used to hearing the mighty Cummins engines in the Dodge trucks. I LOVE listening to those...

grywlfbg · **Posted:** Mon Jan 09, 2006 8:50 pm

We've discussed this in some earlier threads but my $0.02 would be to leave the cat on and intact. I don't know how much it's helping but I assume it's there for a reason (since they're not yet required by EPA regs - DC wouldn't have added cost just for fun). We are in serious danger of losing diesels alltogether with the coming EPA regs - let's try to play nice and not piss off others.

N don't even get me started on aftermarket pipes on motorcycles :evil:

greiswig · **Posted:** Tue Jan 10, 2006 12:31 am

grywlfbg wrote:

We've discussed this in some earlier threads but my $0.02 would be to leave the cat on and intact. I don't know how much it's helping but I assume it's there for a reason (since they're not yet required by EPA regs - DC wouldn't have added cost just for fun). We are in serious danger of losing diesels alltogether with the coming EPA regs - let's try to play nice and not piss off others.

N don't even get me started on aftermarket pipes on motorcycles :evil:

No argument here. But there are two basic types of catalytic design, from the little I understand: pellet (cheap and not good for flow) and honeycomb (more expensive but with better flow). I'm wondering about what the nature of the stock CC is, and whether subbing a better design would be similarly beneficial to mileage and performance. But...that might be at the expense of noise, since the pellet types probably also dampen exhaust pulses better.

boxhead · **Joined:** Fri Jul 08, 2005 11:14 pm **Posts:** 186

I believe ours are the honeycomb design based on an early CRD'er reaming his out. For me personally, I've got enough changes to fight with DC about on warranty issues without messing with the cats.

n3qik · **Posted:** Tue Jan 10, 2006 7:31 pm

Yes, the cat is of the honeycome type.

FarmDiesel · **Joined:** Thu Sep 15, 2005 8:49 am **Posts:** 132

Yeah, once my warranty period is over, I'm going to consider experimenting with different catalytic systems on the CRD. The only downside is that I'm pretty sure I need to wait until the 7/100 warranty is over, and not just the 3/36...

grywlfbg · **Posted:** Wed Jan 11, 2006 1:59 pm

Actually, I'm pretty sure that all vehicles sold in the US must come w/ an 8-year emissions warranty. But if you're not concerned w/ warranty repairs to the emissions system itself then yeah, I'd just wait for the 7-year powertrain warranty to expire.

Exhaust noise and catalytic

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