New exhaust?

RTStabler51 · **Posted:** Mon Jul 06, 2009 8:40 am

stoutdog wrote:

Also, could you link me to where you are finding them for the low $300s? I can find the aluminized, but would only consider the SS.

All I did is a google search with MBRP and their SS part number. I think it was auto accessories or something like that.

stoutdog · **Posted:** Mon Jul 06, 2009 8:53 am

RTStabler51 wrote:

stoutdog wrote:

Also, could you link me to where you are finding them for the low $300s? I can find the aluminized, but would only consider the SS.

All I did is a google search with MBRP and their SS part number. I think it was auto accessories or something like that.

Thanks, found it. Still though, what advantage would I expect to see in replacing the whole system cat back or simply replacing the muffler?...

RTStabler51 · **Posted:** Mon Jul 06, 2009 9:47 am

stoutdog wrote:

RTStabler51 wrote:

stoutdog wrote:

Also, could you link me to where you are finding them for the low $300s? I can find the aluminized, but would only consider the SS.

All I did is a google search with MBRP and their SS part number. I think it was auto accessories or something like that.

Thanks, found it. Still though, what advantage would I expect to see in replacing the whole system cat back or simply replacing the muffler?...

IIRC, the OEM catbach is 2 1/4, I'm sure someone will correct me if I'm wrong. So a bit more volume and better flow with the muffler. In the grand scheme of things, its honestly probably negligible.

stoutdog · **Posted:** Mon Jul 06, 2009 4:22 pm

RTStabler51 wrote:

stoutdog wrote:

RTStabler51 wrote:

stoutdog wrote:

Also, could you link me to where you are finding them for the low $300s? I can find the aluminized, but would only consider the SS.

All I did is a google search with MBRP and their SS part number. I think it was auto accessories or something like that.

Thanks, found it. Still though, what advantage would I expect to see in replacing the whole system cat back or simply replacing the muffler?...

IIRC, the OEM catbach is 2 1/4, I'm sure someone will correct me if I'm wrong. So a bit more volume and better flow with the muffler. In the grand scheme of things, its honestly probably negligible.

I'm fairly certain that all the piping is 2.5" while the muffler shrunk down to 2.25". Anybody know for sure?

Joe Romas · **Posted:** Tue Jul 07, 2009 7:12 am

stoutdog wrote:

'm fairly certain that all the piping is 2.5" while the muffler shrunk down to 2.25". Anybody know for sure?

I think if you measure the inlet to the muffler right at the body of the muffler you'll find out it's 2.25 :lol:

I've read that inside it's also very restrictive.

stoutdog · **Posted:** Tue Jul 07, 2009 8:09 am

Joe Romas wrote:

stoutdog wrote:

'm fairly certain that all the piping is 2.5" while the muffler shrunk down to 2.25". Anybody know for sure?

I think if you measure the inlet to the muffler right at the body of the muffler you'll find out it's 2.25 :lol:

I've read that inside it's also very restrictive.

Right, but I could swear I read that they whole system, excepting the muffler of course, was 2.5." I believe the pipes were pinched down around the muffler to accommodate the smaller size. Grr, now I'm confused.

Joe Romas · **Posted:** Tue Jul 07, 2009 8:25 am

stoutdog wrote:

Right, but I could swear I read that they whole system, excepting the muffler of course, was 2.5." I believe the pipes were pinched down around the muffler to accommodate the smaller size. Grr, now I'm confused.

It's the muffler's input that's pinched down and that's part of the muffler. The rest is 2.5" :wink:

If your still confused, crawl under there and look at the front of the muffler :lol:

stoutdog · **Posted:** Tue Jul 07, 2009 9:01 am

Joe Romas wrote:

stoutdog wrote:

Right, but I could swear I read that they whole system, excepting the muffler of course, was 2.5." I believe the pipes were pinched down around the muffler to accommodate the smaller size. Grr, now I'm confused.

It's the muffler's input that's pinched down and that's part of the muffler. The rest is 2.5" :wink:

If your still confused, crawl under there and look at the front of the muffler :lol:

I'm living in DC for another 4 weeks and my Jeep is back in Florida, hence the issues :wink:

I am probably going to have the shop hack off all the 2.25" parts and replace it with a 2.5" magnaflow. Now, the question is which magnaflow to use.... there are tons of models!

Anybody have a part number for a straight through magnaflow muffler that fits our exhaust?

Turbo Tim · **Posted:** Tue Jul 07, 2009 9:20 am

Before you do any hacking, you might want to consider what I did.
I made some square flanges got exhaust gaskets to match from NAPA. I then cut just before the cat, and then just after the muffler so that whole stock assembly stayed together. I then welded the flanges in so the stock cat and muffler can be put back in less than 5 minutes (if ever need be).
I then put a hollowed out cat and a Flow Master muffler in with flanges also. This makes it easy to weld as it all comes out.
This arrangement will pass the visual SMOG inspection if it ever happens. I chose the 70 series Flow Master because there is nothing to blow out over time. We use these on our off road cars as well over the Magnaflow and other brands.
Let us know what you do.

stoutdog · **Posted:** Tue Jul 07, 2009 7:23 pm

Turbo Tim wrote:

Before you do any hacking, you might want to consider what I did.
I made some square flanges got exhaust gaskets to match from NAPA. I then cut just before the cat, and then just after the muffler so that whole stock assembly stayed together. I then welded the flanges in so the stock cat and muffler can be put back in less than 5 minutes (if ever need be).
I then put a hollowed out cat and a Flow Master muffler in with flanges also. This makes it easy to weld as it all comes out.
This arrangement will pass the visual SMOG inspection if it ever happens. I chose the 70 series Flow Master because there is nothing to blow out over time. We use these on our off road cars as well over the Magnaflow and other brands.
Let us know what you do.

Turbo Tim, thanks for the advice. At the moment, I think I'm going to keep the cat, as most people (including now, GDE) believe it to be generally non-restrictive. Besides, I can only, in good conscience, circumvent so many EPA regulations. I'm going for max mpg not only to save a little cash, but to decrease my own levels of pollution. I can understand the SEGR (or GDE's version of it, which I will soon have), because the mpg gains are significant enough to offset a minor increase in exhaust pollution.

However, I have yet to see anyone gain more than 2-3 mpg by replacing their exhaust, be it a straight pipe, cat back, gutted cat, or simply a new muffler. All seem to yield approximately the same results in the long run - dependent upon, of course, driving style. Gutting or removing the cat doesn't appear to yield much in the way of mpg, only noise and pollutants (see Darby's post).

From a monetary standpoint, gutting the cat, removing it, or installing a catback system makes little sense as well. I've spent the better part of today trolling through other exhaust threads to come to this conclusion. There seems to be an insignificant difference between any of the aforementioned options... all that is really needed is removing the exhaust brake *cough* muffler. I cannot, therefore, justify spending $300+ on a catback or legal secondary system when I could spend around $100 (parts/install) and get the same results.

Make sense? Thanks again for your advice!

Sir Sam · **Posted:** Tue Jul 07, 2009 7:49 pm

While we are on the topic, if anyone removed their cat and doesn't want it, I am accepting donations for my CRD MJ project.

warp2diesel · **Posted:** Tue Jul 07, 2009 9:34 pm

I still have the extra boost gauge between my turbo and cat to measure back pressure when driving. Even with the lousy stock system the boost gauge between the turbo and cat stays at ZERO until I get over 2500 RPM unless I am trailer towing or going up a steep hill. Even when I was towing, I never got the gauge off the ZERO below 2200 RPM.
I will keep the extra boost gauge installed until after I install my Magnaflow Straight through and do some trailer towing.

I hope this puts it into perspective.

CRD Joe · **Posted:** Wed Jul 08, 2009 4:01 pm

Yep, looking forward to my 3" cat back no muffler. The more diesel sound the better! :lol:

stoutdog · **Posted:** Wed Jul 08, 2009 5:08 pm

CRD Joe wrote:

Yep, looking forward to my 3" cat back no muffler. The more diesel sound the better! :lol:

My understanding is that the diesel sound only comes out if you remove/gut the cat... the muffler just deepens the tone.

And, to quote another member, his 3" no muffler system sounded like "an old jalopy." Rackety Rackety Rackety. Let's face it, the CRD is not meant to and will never sound like a Cummins.

DarbyWalters · **Posted:** Wed Jul 08, 2009 6:04 pm

I have a 3" catback...exit in stock position and it sounds great. Not like an
"old jalopy" in any sense. People always ask me, "That sounds like a Diesel!!!"

CRD Joe · **Posted:** Wed Jul 08, 2009 6:09 pm

DarbyWalters wrote:

I have a 3" catback...exit in stock position and it sounds great. Not like an
"old jalopy" in any sense. People always ask me, "That sounds like a Diesel!!!"

Now that's what Im talking about!

Give me noise and lots of black smoke and Im happy! :lol:

Joe Romas · **Posted:** Wed Jul 08, 2009 6:32 pm

CRD Joe wrote:

Give me noise and lots of black smoke and Im happy! :lol:

And you'll help continue the bad opinions most people have about diesel engines :lol:

stoutdog · **Posted:** Wed Jul 08, 2009 11:39 pm

Joe Romas wrote:

CRD Joe wrote:

Give me noise and lots of black smoke and Im happy! :lol:

And you'll help continue the bad opinions most people have about diesel engines :lol:

x2 No mpg gain + worse for the environment = not worth the $$$ + bad for the diesel image

CRD Joe · **Posted:** Thu Jul 09, 2009 2:00 am

Come on guys, would you relax? There isn't anything I can do to produce black smoke, besides I run bio diesel! As for other people and their perception of diesel vehicles, I don't care what other people think! I give diesel positive feedback by my Jetta getting 62mpg and my KJ getting 38mpg and advertising those facts. People are always asking me about my high mileage vehicles and I proudly offer explanations as to how they too can get these high mileage vehicles. Let's be clear, with our current Marxist America hating president and his war on capitalism and the private sector along with his EPA global warming administration we and our diesel vehicles are an endangered species!

How's that hope and change working for you?

flash7210 · **Posted:** Thu Jul 09, 2009 8:23 am

I've thought about gutting the cat several times.
I dont think I will go through with it though.
I dont think there is much performance to be gained and I like knowing I
can easily put things back to stock at any time when necessary.

Removing the muffler was one of the first mods I did.
I bought an exhaust flange and tip from Summit. I removed the cat back
and left it at home while I drove to the exhaust shop. I gave them the
flange and tip and they welded an elbow together so the exhaust comes
out the side in front of the RR tire. Total cost, parts+labor, ~70 bucks.

Now, should I ever need to put the muffler and tailpipe back on, I just
unbolt the short-pipe and put in the old exhaust.

My wife, although she hates to admit it, now likes driving the Jeep. She
likes the sound it makes and likes all the available power.

New exhaust?

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