true straight pipe

dieseledkj · **Posted:** Tue Jul 31, 2007 12:03 am

I have noticed that several people have cut off their mufflers but left the cat. Has anyone run true straight pipe (no cat / no muffler) or just a straight through muffler. I have a local shop that will remove everthing from the downpipe back and will set it up so I can reinsatll the stock system if its needed. I'm pretty sure I will run an open muffle of some type, just not sure until I hear it.

bugnout · **Posted:** Tue Jul 31, 2007 9:17 am

I've got a Cherry Bomb installed, I can now hear the turbo spooling, Way cool, but other than that not much additional noise. Still have the Cat. I think it gave my CRD a little more jump, or maybe that turbo sound just makes me think its jumping faster. :wink:

Stan Wright · **Posted:** Tue Jul 31, 2007 9:43 am

http://liberty.eurekaboy.com/magnaflow2.htm

I put a 3" straightpipe on mine but it was too noisy. Sounded like an old junker. I put on the smallest 3" muffler Magnaflow makes and now it sounds nice.

Johnboy · **Posted:** Tue Jul 31, 2007 10:12 am

Having read this thread, I am still not clear if any of you have removed the cat conv. I cut out the muffler and put a piece of pipe in. Sounds a littel better, only 10-15% louder so it is not obnoxious at all. I have been wondering about cutting out the cat conv also. Cant find any wires (indicating sensors...) so shouldnt throw any codes... How much muffler effect (sound) does the cat conv. have?

nix · **Posted:** Tue Jul 31, 2007 10:51 am

Do diesels have o2 sensors like those found on gasoline powered vehicles? Gasoline powered vehicles usually have one before and after the cat.

UFO · **Posted:** Tue Jul 31, 2007 11:01 am

nix wrote:

Do diesels have o2 sensors like those found on gasoline powered vehicles? Gasoline powered vehicles usually have one before and after the cat.

No. Diesels burn fuel with an excess of O2, so an O2 sensor will tell the computer nothing.

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

It is turboed, and the turbo acts like a muffler, so I don't think that removing the cat is going to make it significantly louder, if that is what you are going for.

dieseledkj · **Posted:** Tue Jul 31, 2007 11:08 pm

When I cut the muffler on my 03 Dodge it did not change anything. I removed the cat then all H_LL broke loose. The cat was holding back all the sound back for sure. I now have a flow through muffler and it lowered the noise 30-40% over no mufffler or cat. I was worried about this libby engine having a backpressure sensor like the 6.0L PSD. I spoke with a guy at Disesl Dynamics and he told me it did not have any type of sensor in the exhaust system. He suggested to go with 3" pipe from the downpipe back and add a good quality muffler. I think i'm going to have my local exhaust guy build me a system that I can take off and re-install my stock stuff for warranty work. Thanks for all the info so far guys!

bentrod · **Posted:** Wed Aug 01, 2007 3:55 pm

I too installed a straight pipe, and then went back to stock. The CRD is not just lound..it makes that awful drone sound that rings deep in your head!

I have played with lots of diesel too-they all sound different. Main reason is what kind of turbo/turbo turbine housing is on it.
Our CDR just so happens to have the VG turbo and its variable vains lets lots of sound/noise right by.
In retrospect my 93 Dodge Cummins had no wastegate on on it at all-nothing but sweet music comes out of that straight pipe.

I say don't loose the cat.

McMoney · **Posted:** Wed Aug 01, 2007 6:24 pm

I was just goin to cut out the muffler but when it was up on the lift i decided to make it all go. Yes i am cat free. It is a little loud and i will be putting some muffler on..... but i will do that when i have the money for a custom 3 inch header back. Sounds really nice at idle but wot it is a loud... waking the dead :twisted:

After driving for a while you get used to the noise. Dosnt seem as loud to me anymore.

I was talking to someone about my crd and they said they could tell it was a diesel by the noise and i said it was quieter before i removed everything.

They also said engines need a little back pressure to work properly but i just figured the turbo made the backpressure so it should be ok. So far so good.

UFO · **Posted:** Wed Aug 01, 2007 7:43 pm

McMoney wrote:

I was just goin to cut out the muffler but when it was up on the lift i decided to make it all go. Yes i am cat free. It is a little loud and i will be putting some muffler on..... but i will do that when i have the money for a custom 3 inch header back. Sounds really nice at idle but wot it is a loud... waking the dead :twisted:

After driving for a while you get used to the noise. Dosnt seem as loud to me anymore.

I was talking to someone about my crd and they said they could tell it was a diesel by the noise and i said it was quieter before i removed everything.

They also said engines need a little back pressure to work properly but i just figured the turbo made the backpressure so it should be ok. So far so good.

You are absolutely right. The best backpressure for a turbo is ZERO.

true straight pipe

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