Does a cat back exhaust really improveexhaust flow or would I be better off replacing the muffler?

 

Most people on the forum will do a turbo back exhaust. This will definitely improve flow while decreasing EGT's. It is your choice to run a muffler or cat from that point on.

 

I recently change my exhaust with a 4" MBRP exhuast. Cat delete and new down pipe, with the muffler. Truck sounds great and has even picked up about 1 or 1.5 mpg with crappy winter blend fuel.

Do it. Call the guys at DPPI and "git r done"!!!! You won't be disappointed.

 

Well, cat back exhaust is pretty much running pipe from your cat into a new muffler with a new midpipe and tailpipe right? The thing to do is go complete full turbo back with a muffler delete and to get max flow go with a cat delete aswell. The only ristriction would be from bends which is pretty nill. I have no cat but still have a muffler. It's sweet.

 

I did the same as sawboy stated above. MBRP straight back no muffler and no cat. Lots of whistle below 2000rpm and lots of rumble above. The turbo seems to spool faster too. I wouldn't worry about the high end expensive stainless too. Living under a daily driver they all are covered with road grime in about a week and I only have the patience to scrub the tip.

 

The reason I asked about cat back is I don't want to void my warranty. So the question is is it worth doing a cat back or should I leave it stock.

 

I saved my cat and can swap it back in if I think it's absence will affect warranty work. Another consideration is alteration of the emissions equipment is view as less than legal.

 

Are you worried about the downpipe. It took me a couple of tries but the dealer in the town down the road said they were cool with it, so i am patiently waiting on the 3.5in MBRP down pipe from DPPI. Most dealers dont like the idea of you messing with the downpipe.

 

Are you going to leave your cat?

 

I went with a turbo back 4 inch stainless margna flow exhaust and muffler that is really a staright through. It has the nice turbo whistle at lower R.P.M. and it will bark when u walk on it. I don't think not having the cat in it will not cause as much arguments on your warranty as it does on gasoline engiens as on diesels the cat is not really that effective any ways. I agree it may not be so legal in all area's but it doe s increase the performance alot and even with a bully dog tuner and outlook monitor on my truck running it in the tow mode, i have not seem the egt's go above 660, although it is winter and not pulling right now.
I just got the truck in sept. it is an 05' 6.0 and i put the tuner on after the exhaust, but with the bully dog i can switch from the tow performance extreme modes or back to stock on the fly.
One thing to note too is now bully dog has the de fueling capability in the outlook monitor for egt and engine coolant temp and also transmission temp's so i don't feel so bad running a bully dog tuner now

 

I deleted it with a test pipe from Pure Diesel Power. It is a bolt on replacement pipe so if i need it to go in for warrenty work, i just bolt the cat back in place and take it in.

 

You can also mod the cat by making it a straight through pipe with just a bit of welding. It will fool the casual observer unless it is removed.

 

I had high hopes of getting a straight answer to your question because I had the same question! C'mon guys yes or no is the Cat-Back worth the money in your opinions? Does it lower EGT's? It must to some lesser degree right? I sure wouldn't expect a performance difference but I personally don't want to have to replace things when I visit the dealer. Somebody out there is running a Cat-back right?

 

Yes a cat back will lower your EGT and this is a benefit if you tow. The turbo back system will lower the EGT about 50-75F lower than the cat back system.

Something to consider, if you travel alot you may require warranty work at a dealer that is not mod friendly, and FMC does not like Turbo Back systems and has been known to void warranty repairs do to this. FMC does not have issues with a Cat Back system, so this is a safer warranty route to go.

If you do not tow much then the lower EGT will be of little benefit, the only other benefit of an A/M exhaust system is a different sound. MPG & performance gains will be slim to none on a stock or lightly modded engine.

Another option is to just replace the factory muffler with a "Walker BTM" muffler, which do to its better flow characteristics will reduce the EGT as well. If you do not mind increased noise, you can just straight pipe it from the Cat back.

Removing the Cat (legalities aside), only sees about 1-2Hp gain, and increased whistle. The downside to removing the Cat is it will cause warranty issues since any professional mechanic working on a vehicle with disabled emissions equipment can recieve a hefty fine from the Feds.

 

Just FYI I have a 4" turbo back MBRP exhaust. I am currently having some turbo issues. Sounds like the bearings are drying up. I decided go to the dealership where I have purchased two trucks and a possible third just to have a listen. I do not get my service done here however. I also do not have a cat. The tech told me that no work would be covered under warranty because I have an after market exhaust. I let him know that I would never buy another truck from them and I would have whatever work done elsewhere. Luckily another dealership is much more mod friendly. But if you don't have many options I would be careful because this could have meant some big bucks for me. All over an exhaust which actually eases the strain on these motors.