Exhaust Mod. Cat delete? Muffler delete?

lacrosseman2010 · **Posted:** Fri Feb 27, 2015 12:06 pm

Hello looking for some opinions on any exhaust mod. Would like the pros and cons of straight pipe from turbo back and from cat back. high flow muffler? What exhaust set ups do you have?

Stan Wright · **Posted:** Fri Feb 27, 2015 1:30 pm

From the factory the restrictions are the small factory muffler and the pinch point between the muffler and the converter. I've tried several different versions...2 1/2"...3"...muffler, muffler delete...cat, cat delete. If I were to do it all over again I would replace the muffler with a 2 1/2" Magnaflow muffler (removing the pinch point also) and keep everything else stock.

MM53 · **Posted:** Sun Mar 01, 2015 11:28 pm

Yes on the Magnaflow muffle get rid of the cat

ATXKJ · **Posted:** Mon Mar 02, 2015 12:22 am

unless you clogged up the Cat - there's no point in removing it - it's not a restriction.

WWDiesel · **Posted:** Mon Mar 02, 2015 7:14 am

Get rid of the choke point and the cat, both are restrictions, install 2 1/2 pipe inlet to muffler, install 2 1/2 inlet / outlet Flowmaster or Magnaflow muffler. This will improve turbo spool up time giving you a little more power and better fuel mileage if you keep your foot out of it. Sounds great as well... :wink:

Any restriction removed from behind the turbo lowers system backpressure and will lower EGT coming into the turbo...
Proved this on my Dodge Cummins with 5 inch turbo back exhaust system!!! Works for all diesels...
:2cents:

Diver1430 · **Posted:** Mon Mar 02, 2015 11:34 pm

I cut mine out and put in a summit street muffler. No noticible performance increase, but I have theGDE tune, weeks mod, etc. sounds good.

diesel_guy86 · **Posted:** Tue Mar 03, 2015 7:23 am

I did 3" straight pipe from the turbo back (I have a different turbo so I have a 3" downpipe too). I ended up having to put a muffler on because it was so loud. I think the large bore combined with the aluminum head on these motors make the exhaust note really deep. I used a MagnaFlow 3" straight thru muffler.
here's a startup vid before the muffler: http://youtu.be/9FmT0nS7HCM

And a drive off: http://youtu.be/jH66n06LsmM

I don't have any vids of after the muffler.

DarbyWalters · **Posted:** Tue Mar 03, 2015 12:30 pm

I did a 3" catback straight tube years ago with no issues. Saved the price of adding back a muffler and it sounds pretty good IMO. You could always go back and add a 3" Magnaflow later if the noise is not to your liking.

ibedonc · **Joined:** Mon Feb 12, 2007 2:40 pm **Posts:** 236

Darby , you still in Texas ?

I ask because they are not passing Diesels with Cat removed now , at least that is what I was told by one place I went to , I still have one guy that will do it but is it a ways away from me

papaindigo · **Posted:** Wed Mar 04, 2015 8:56 am

As hinted by ibedonc don't totally get rid of the cat. You may move, you may sell, or inspection requirements might change to where at least the appearance of a cat is required. As I understand it in theory you can gut the cat and keep it in place or in theory you can remove it and store it just in case. There have been at least a few forum members who have had to acquire cats to reinstall.

FYI - lots of restriction chat but I'll point out again that there are 2 restriction points upstream from the muffler/cat. Frankly I would not bother with anything other than a less restrictive muffler.

95Z28A4 · **Joined:** Sun Mar 30, 2014 9:53 am **Posts:** 297

Has anyone tried the NELSON GLOBAL PRODUCTS 86675M OVAL MUFFLER? This muffler is the stock replacement for an early/mid 1990's Ford F-250/350/E-350 7.3L pre/early PowerStroke diesel. I think if it can handle a 7.3L diesel, it should have adequate flow for our 2.8L VM.

Ebay link
http://www.ebay.com/itm/NELSON-GLOBAL-P ... #vi-ilComp

Nelson Exhaust Products Catalog (Look on page 3-8)
http://www.nelsonglobalproducts.com/cat ... 0Final.pdf

I will leave our CRD's exhaust stock for now. I am currently assembling a used oil filtering/centrifuging plant. I want to burn a blend of filtered/centrifuged waste motor oil and #2 diesel in my 1998 Dodge 12 valve Cummins and in our 2006 CRD. At that time, I will remove the cat and stock muffler and install the NELSON GLOBAL PRODUCTS 86675M OVAL MUFFLER (or maybe another muffler, If I find one better). If it drones or is too noisy, I will install a resonator upstream of the Nelson muffler. This Jeep is my wife's daily driver. She likes it.....especially likes it since I installed the GDE FT ECO tune. I think she won't like it if I make it noisy.

Mountainman · **Posted:** Wed Mar 04, 2015 8:01 pm

papaindigo wrote:

As hinted by ibedonc don't totally get rid of the cat. You may move, you may sell, or inspection requirements might change to where at least the appearance of a cat is required. As I understand it in theory you can gut the cat and keep it in place or in theory you can remove it and store it just in case. There have been at least a few forum members who have had to acquire cats to reinstall.

FYI - lots of restriction chat but I'll point out again that there are 2 restriction points upstream from the muffler/cat. Frankly I would not bother with anything other than a less restrictive muffler.

X2, or no muffler!

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

Please leave the cat in. Not a major restriction anyway. The muffler is the biggest restriction, since it necks down and back up again. Cut it out and replace with a straight pipe, or a muffler or resonator and you will basically have a 2.5" turbo-back exhaust. We will have muffler delete kits available this spring for anyone interested.

Here is a clip (not mine) of the sound different after a muffler delete (cat in place, muffler deleted):

http://www.youtube.com/watch?v=xlOBuliKo_M

mass-hole · **Posted:** Sun Mar 15, 2015 8:56 pm

I had my muffler cut out, but I am going to have a 2.5” put back in place. Around town is OK, but its annoying when your cruising along at 2200 rpm on the freeway for any amount of time longer than 30 minutes.

WWDiesel · **Posted:** Mon Mar 16, 2015 6:09 am

Quote:

Please leave the cat in. Not a major restriction anyway.

Some on here have obviously never experienced a partly or fully stopped up CAT?
They CAN BE a major restriction or choking point in an exhaust system.
If you can, remove it completely, or even gut it and put it back to pass any visual inspections.
Best option, replace CAT and choke point with straight pipe, install a free flowing muffler like a Flowmaster or one of the other brands. 2.5 inch from turbo back to exhaust tip!!!! :-)r

ANY back pressure in the exhaust system affects turbo performance and EGT's! So, the lower the back pressure, the lower the EGR's and the better the flow rate leaving the turbo...
From experience on my Cummins, now 5 inch turbo back...

cevans · **Joined:** Wed Aug 24, 2005 12:48 pm **Posts:** 278

WWDiesel wrote:

Quote:

Please leave the cat in. Not a major restriction anyway.

Some on here have obviously never experienced a partly or fully stopped up CAT?
They CAN BE a major restriction or choking point in an exhaust system.
If you can, remove it completely, or even gut it and put it back to pass any visual inspections.
Best option, replace CAT and choke point with straight pipe, install a free flowing muffler like a Flowmaster or one of the other brands. 2.5 inch from turbo back to exhaust tip!!!! :-)r

ANY back pressure in the exhaust system affects turbo performance and EGT's! So, the lower the back pressure, the lower the EGR's and the better the flow rate leaving the turbo...
From experience on my Cummins, now 5 inch turbo back...

I'm curious to hear from some people who have done free-flow exhausts on the CRD. For one, back pressure can actually be a good thing for control of turbocharger boost pressure. When you take the back pressure away, you increase the difference in pressure pre and post turbo, and increase boost spikes and boost creep potential. All of this is dependent on how tolerant the factory design is, so, I want to hear from owners who have free flow to see how their boost response changed.

Squeeto · **Posted:** Wed Mar 18, 2015 4:52 pm

papaindigo wrote:

... I'll point out again that there are 2 restriction points upstream from the muffler/cat. Frankly I would not bother with anything other than a less restrictive muffler.

Had to go back and find your original post on this!
2 inches out the back of the turbo and 2-1/4 at the first bend makes the pinch/choke point less of a worry.
I hope that this does not go unnoticed.

Exhaust Mod. Cat delete? Muffler delete?

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