gasser76

Hi all,

How many of you have replaced the muffler with a straight pipe (cat still installed)? Any long term issues or benefits ... other than the sound?

I thought I read somewhere a while back that the exhaust gas temp would lowers some, which is good. Is that true?

Thanks,

rockcrawler304

I pulled my muffler off almost a 100k miles ago. No benefits or down sides to it. "Maybe" a few degrees cooler on EGT's which is good but not enough to actually notice. I did it for the sound is all.

1-2-3

I've never ran muffler on either of my CTD's. The muffler off the 99 laid by the garage for years. Only thing that ever happens is people complimenting on how good it sounds. Take out your silencer ring in the turbo too. You'll get a hint of the turbo spinning/whizzing. Won't affect anything on the engine, besides sound.

jstone44720

Long term, I think it is fine for the engine mechanically, but bad for diesel motorsports overall. The more attention we attract, the more likely we will have to deal with increased hassle from from various govt. groups. Mine will have a muffler again soon, as I keep getting dirty looks from the neighbors.

tslewisz

I pulled mine off and replaced it with an Aeroturbine. When that split I just put a straight pipe on it. It's not TOO loud since the cat is still on. I like it fine.

When I did it I didn't have a pyro, but most people on the forum were saying the muffler was more restrictive than the cat and would keep EGT's a little cooler.

Grit Dog

Same.
My truck still has the cat and resonator and sounds good with NO exhaust drone when towing or running it hard. Good middle of the road combo IMO. A buddy's 3rd Gen compeltely straight piped is LOUD and the drone is almost unbearable when towing.

NickBeek

I replaced my factory muffler with an MBRP straight through muffler. No drone and quiet as can be inside the truck, out side it sounded just right. Then I did stacks with no muffler, that lasted exactly two towing trips before I put the MBRP muffler back in the mix... It was stupid loud in the cab when towing. All this has been with the cat in place and functioning.

Pull Dog

I can tell you my experience with the exhaust system on my 05, this is all I have to go on since this is my first diesel. My truck was bought 5 years ago with 23K miles and the previous owner had removed the cat, put a 5 inch turbo back system on it with a fake muffer. The immediate effect I noticed of course was that it was loud, very loud. I was aware diesels were loud and I wanted this spottless clean truck bad enough to go ahead with the deal. I did ok with the noise until I towed my 5th wheel. The noise or drone inside the cab was unbearable. It hurt your teeth!!!! Again, this was my first diesel and the experience of pulling with all that torque was great but I knew within the first 10 miles of towing that I would replace the system.

The first thing I did was contact the Dodge dealer where I bought the truck and became very firm with him that he had sold me a truck non compliant with EPA requirements and he did not make me aware of this prior to signing. He immediately agreed to ship me an OEM cat and I agreed to have it installed at my cost. This thing is like several hundred dollars and the size of a beer keg!! I put it on and noticed no difference in MPG (hand calculation) or seat of the pants power. Then I ordered the stock 4 inch exhaust and muffer...OEM...and installed it myself. Now I was back to a totally stock truck. I checked very closely for several weeks and noticed absolutely no difference in MPG both towing and non towing highway and local driving. It was much quieter but yet has the very familar Cummins sound. There was absolutely no drone when pulling hard.

I have no idea why people want to tinker with these trucks, spend thousands of dollars on enhancements and void their warranty. These trucks pull and pull hard, are very reliable and sound gutsy. I'm sure that if attached to a dyno you could see differences in power and EGT but my seat of the pants experience tells me you don't gain any substantial difference other than noise. I agree with those posters who have stated we don't need to draw attention to ourselves with noise.

Diesel manufacturers are coming up with new engines all the time, the new Fords sound like a gas engine. I'm not against the sound of the stock Cummins but when passengers in the back seat tell me the fillings in their teeth hurt someone has made a mistake in enhancing the truck!!

tantruck

Not a straight pipe but I have the MBRP muffler behind the Cat on my 2007 and it is quiet and has just enough tone when you accellerate to sound good. I have tried many combinations on my 2004.5 and come to the conclusion that even with a resonator in place of the Cat and a MBRP cat back muffler it's too loud at highway speeds towing. I do have a SPS 62 turbo which lets a bit more noise through.
That said I am seriously thinking of putting the Cat back on my 2004.5 for a little more peace and quiet but then I'm getting older and tired of all the racket.
It's fairly cheap to try the muffler delete and if that doesn't work leave the Cat and do the muffler back thing. It's just a pain to take the exhaust apart unless you use the stainless steel band clamps which I highly recommend.

They work great and they make both types, one for butt joints and one for lap joints. Even the butt joint style will stretch / deform enough to seal the lap joint when you tighten the heck out of them.

I believe several manufacturers carry them but I've had good luck with Walker 4.00 inch band clamps I got at Summit:

Walker Exhaust 33280 - Walker Butt-Joint Band Clamps -
Overview - SummitRacing.com (These are the butt joint style or smooth straight type)
http://www.summitracing.com/parts/WLK-33280/
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or
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Walker Exhaust 33224 - Walker Torctite Exhaust Clamps -
Overview - SummitRacing.com (These are the lap joint style, - kind of hard to see the step in the clampin this photo)
http://www.summitracing.com/parts/WLK-33224/
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Not too expensive and allow you to disassemble when needed as opposed the the traditional "u" style muffler clamps which deform, (crimp), the exhaust pipe making it difficult to separate.

Just my 2 cents.

Grit Dog

I didn't void my warranty by removing just the muffler (but I'm sure the PO did the day he drove it off the lot and put a Bullydog on it! haha)

If you dont like rolling down the passenger back window when going thru a tunnel or under an overpass and tromping on the go pedal then you probably won't understand. If you do, then you will understand!

gasser76

Thanks guys for posting the replies! I am going to order a muffler delete kit, I think. It seems to be the perfect balance and should achieve that deeper & throaty tone.

RamGazer

I wish I knew what I could do in order to get some quite in my truck. Like I posted in another thread I started the more miles I put on my truck the louder it gets inside the cab. I like the outside sound just not the in-cab noise (the air vibrates and it gets hard to understand someone else talking).

cdennyb

Since I have a Donaldson muffler you can basically see thru like an old time glass-pack, I chose to delete the CAT and keep the muff for sound control, (I run 6" stacks) and the muff has far less back pressure than the CAT does. I have put pressure gauges on upstream of both and downstream and measured so I know for a fact.
Tried the whole straight pipe thing but pulling a 40' enclosed 3-axle car trailer made it hard to talk or listen to the stereo with the windows down.

1-2-3

Mine is 4" all the way. I have no idea what y'all call drone is. I absolutely love the way my truck sounds and if there was a radio station that played the song it made going under bridges, I'd have it set to that station and pull off the **** so nobody could change it. If you don't understand why i would like that sound all the time, I guess it's the same as i don't understand how somebody could listen to rap music all the time either. I waited on my 99 to open it up till the warranty ran out, and the 04 was already done when I got it.

gasser76