Engine/Transmission (1994 - 1998) Catalytic Converter ?

[SteveAnsley]

I have a '98 12 valve w/ 105,000. Stock exhaust w/ the cat in place and no muffler.



I was wondering how much of a concern is there w/ my cat being plugged-up w/ soot and causing a loss of performance?

I'm getting different opinions from muffler shops, some shops say a diesel isn't going to cause any flow problems; others say the soot from a diesel will plug a cat.



2nd ?

Will a cat also work as muffler w/ regards to exhaust noice/tone/resonance?

As mentioned, this truck does not have a muffler, only the cat. What kind of sound difference would be expected from the cat as opposed to without?

 

[Dieselnut59]

I don't know how one sounds with only the cat, but it has a nice sound with only the muffler and (in my opinion) a very nice sound with neither. It does have a "growl" at around 2000 rpm with the factory downpipe. 4" downpipe cures that. I would highly recommend a full 4" system if you straight pipe it. My cat from my 1996 has about 200 miles on it. When I picked up the truck, I got the factory "delete" pipe (used on 1993 built 1994 models which came with no kitty). The truck now has right at 200,000 on it and has gone through several exhaust experiments before the one I love, full 4" with the dual stacks.

Got full 4" on the '03 with a straight through muffler and a home made 3 to 4" straight pipe system on the '98 work truck.

By what I have noticed, cats can plug up. The one on a previous '98 really looked bad when I took it off and performance was greatly improved after removal. If you can get away with it, 5H1Tcan the kitty.

 

[TPCDrafting]

I took my cat off at around 90-100k miles. It wasn't plugged and I didn't see any performance, mileage, temp. improvements. The exh. is a little louder, not much, but the pacbrake at idle hisses louder than before.

 

[cumminsnbabes]

Cut it out. it can only help and definitely won't hurt anything. my truck is straight piped clear thru and sounds awesome.

 

[EBottema]

Having a cat is a restriction. With it gone it will make it a little louder of course but will drop EGTs very slightly and maybe give you a little better fuel economy... .

 

[mschoenheider]

There was a noticable sound difference when I put the cat back into my 4" system for emissions. Without the cat, the 4" was pretty raspy and loud. With the cat added back in, the 4" is louder than stock, but not objectionable. No detectable difference in EGT with it back in there, so I left it on. I did chop off the 3" inlet to the cat back to where it tapers out to 4" and welded on a 4" piece of pipe for the inlet. I understand this probably doesn't flow as well as a 4" cat from the newer trucks, bit at least I don't neck down to 3" anymore.

Mark

 

[JGK]

If you take it out, keep it around. Some states are getting anal with their emission testing. I tested 2 or 3 years just fine without mine until last year. Then I had to put it back on to pass the test (visual inspection). 'Course, it's a rather gutless cat, but it passes the test



-Jay

 

[MHalloran]

If you take it out, keep it around. Some states are getting anal with their emission testing. I tested 2 or 3 years just fine without mine until last year. Then I had to put it back on to pass the test (visual inspection). 'Course, it's a rather gutless cat, but it passes the test



-Jay

Jay, what was your technique for guttin' your cat? Easy? Mike

 

[EBottema]

Jay, what was your technique for guttin' your cat? Easy? Mike

Use a air chisel and start beating the inside of the cat apart. It will shatter since it is just metal fibers. use a chisel and do this over a trash can!

 

[Forrest]

Jay, what was your technique for guttin' your cat? Easy? Mike

I used a loooong 1/2" socket extension & hammered away. :-laf . Ditto what EBottema said. The guts break up after a couple passes through it. When I had mine removed, he kept 2" or so of pipe on either end. I just stood it up on the driveway, 4" side down & hammered away.



Wish I had the air chisel. Last whack of the hammer with a tired arm ... didn't hit the bar straight on ... hit the side of my left hand.





Forrest

 

[EBottema]

Oh by the way. The metal and fiber material inside the cat is bad for you. After your done, wash your hands and try to wear a particle mask



erik

 

[JGK]

Sorry for the delay in replying... I haven't been on the 'net since last week.



Yeah, it was several years ago. I used a 3' long straight pry bar with one end that was pointed. Took me about 45 minutes. I stood it on end on a wood block in the gravel driveway and worked at it from both ends. Mine seemed to be a sort of ceramic honey comb. Didn't look metallic in any way.



In any case, once you get a good hole through the middle, work at simply making the hole bigger and bigger. Eventually it will break loose and fall out.



I suppose, once you had a 4" hole down the center, the rest could stay in place if you wanted.



To get it to work with my 4" exhaust I had to cut off the 3" end and weld on a piece of 4" that the local muffler shop flared for me. I used the 4" wide band clamps to put it in just in case I wanted to remove it again in the future. If I ever do twins and go to a 5" system, it'll look like just a swelled spot in the piping!



-Jay

 

[MHalloran]

Guys... Thanks for the replies. I asked Mark @ DPPI also about the cat & if it was necessary. He said on my truck (a 96) it would be a resonator, not a cat. Guess that would explain some guys seeing metallic insides & some seeing honeycomb. Cats on some (maybe newer) and not on others --kinda strange. I always connected gas engines with cats. Diesel also? A resonator makes sense.

 

[EBottema]

Fed law required 96 to have a CAT. I think mark is mistaken. Anyone else ?

 

[Forrest]

I think you're right. Mine is a 96 & it's a CAT. Here's some pics. edit ... WAS a cat.



It's been "tweaked" to mate up to the 4" outlet :-laf

 

[SteveAnsley]

Well the straight pipe was a bit too much for me. A bit too loud and had a terrible drone at highway speed.



Had my muffler guy put in a Flo-Pro 7" round muffler yesterday, much better.

Has a nice rumble, without being too overbearing.



There is a a little bit of a drone between 1600-1800 rpm's. Going to hook the boat up later if I have time and see if the drone is more noticeable with a small load. Might play around w/ alum. angle clamped to the pipe in various spots.



Side Note: The muffler does exhibit a rattle from the gases flowing through. Not bad, just noticeable. What about a high-heat insulated mat wrapped around the muffler?

Any suggestion as to a good / not-too-expensive material that might work?



Edit: The cat was a bit plugged w/ soot. First thing I noticed was the truck did not decelerate when letting off the accelerator the way it would when the cat was there, apparently the cat was acting as an exhaust brake to a small degree. Drives noticeable better and with a smooher idle. Seems to idle about 50 rpm's less. The idle was never bad, but seems VERY smooth now; kinda glad it has a bit of a rattle so I know it's running.

 

[TravisG]

Forest- What is that donut lookin thing on the tailshaft of your transfer case? Between the U-joint and tail housing. I don't think I have one of those.

 

[Forrest]

I don't know Travis. I see you have a 4x4 too, thought it may be that.

 

[Andy Redmond]

balancer for the driveshaft

 

[TravisG]

Oh- Thanks Andy. Why don't I have one of those?