Getting ready to buy a 4'' exhaust system for my 06 PSD.which one do I buy?I need it to be quiet on the inside but dont mind a little rumble outside.I am looking at the mbrp cat back system. What do you think?

 

Thread moved to 6.0L PSD section.

 

Well, allot depends. First, I assume you have an automatic trans. cause I think I'm the only one here running a manual. So that solves at least one clearance issue. THe stock down pipe is 3" from the turbo to right before the cat, so if you don't increase the size of the downpipe, your not really doing much acept changing the way it sounds. Now, there has been some debate over this dealing with "backpressure" issues with the turbo, but it's all unsubstanciated and I beleive you'll be better off with a larger down pipe (I was).

MBRP does make a nice system, especially with the cat delete section that some people prefer. However, it's just as easy to make your own section with some pipe and two band clamps. Bully Dog has a system that is easily converted with this method, if it fits your truck. It sure didn't fit my truck! the down pipe hit the transmition, and the intermediary hit the front leaf spring shackle and transmition mount/frame cross member. It was a mess to fix. But, it might slip right in to your truck, having an automatic.

Here's what I would do if I could do my truck over. With the brand of your choice go 4" turbo back, with no cat, and no muffler. IT'S NOT THAT LOUD! I thought it would be loud too, but I put 5,000 miles a weekend on my truck, and I hardley notice the difference. You will notice a big difference when you nock the rag top off that little import next to you when your in town...and that's what we all want!!

 

From experience--the backpressure issue has been beaten to death--it's a MOOT POINT and means nothing. 3.5" downpipe will make you spool a little faster from a stop. 4" will give you better flow on top end and may be a little louder out the tailpipe. I have the 3.5/4" magnaflow straight piped. rumbles a little going down the road and roars when you hammer it. It whistles at idle just a little.

 

I have the MBRP 4" Turbo Back. I like it. The sound in the cab isn't much more than stock. The sound outside is nice. I still have the cat and muffler. I am happy with it after about 2000 miles.

 

I have the MBRP Off-Road package. The top piece of the downpipe is 3.5" and the bottom piece transitions to 4". It doesn't give you the option of keeping the cat. It has a great rumble on acceleration but quiets down nicely when you level off.

 

Island Doc,

Be sure you get a system that lets you bolt the cat in and out if the system if you go turbo back, which is reccomended for make EGT reduction and best CFM flow rates. The MBRP and AFe are the only two system that I am aware of that let you bolt the cat in totally un modified, this keeps the dealers happy. You can be racing and in twenty minutes be "legal". With the cat in you'll get a good rumble when it's floored, and a nice increase in turbo whistle. Cat out you'll get 15% more rumble and whistle!! Running catt'ed and cruising it's real close to stock!

Call us if you have any questions we'll be glad to help you.

Mark @ DPPI

 

The cat is 3.5 inches on both sides. So, any turbo back 4" system, whether is has a 4" down pipe or 3.5" down pipe, and is designed for the cat to be a part of the system it will be attached with clamps. The Cat can be replaced with a piece of 3.5" tubing (the same as the stock piping you took out). So you can just cut a piece of your stock exhaust and slip it in...and whalla.....Cat delete pipe. Free. Downside, at least in my system, I have the Banks monster exhaust is that it has a 3.5" downpipe, tapers to 4" BEFORE the cat(or lack of cat) then flares down to accept the 3.5" cat then AFTER the cat starts 4" and continues 4" out the back. No idea what that does to performance, but I LIKE IT! Lotsa choices.....

 

badbrad60,

You're right you can do that with a piece of 3.5 inch pipe, but if you mod the cat you have technically voided the emmissions law. To do what you suggested you have to cut the flange off o the entry of the cat. That's why we promote the AFE and MBRP systems as the cat is not cut or modified in any way and bolts in using the stock flange etc.

Mark @ DPPI

 

Good point Mark. Banks system requires you to cut the flange off the cat. This system is obviously different than the AFE and MBRP...