When I put an MBRP 5" exhaust on my Cummins it bolted right to the turbo outlet. From what I've noticed all the Duramax "Turbo back" exhausts don't mate to the Turbo but to the downpipe off the Turbo which is still a stock "restrictive" pipe.

Does any exhaust vendor make a 4" downpipe to use in conjunction with an MBRP or a Corsa system. I aslo noticed it might be a challenging proposition to get that pipe in place if there was one. Clearance looks real tight up against the firewall.

Any experience with this?

Mike

MBRP , Kennedy are a few

there is only one and it comes with the a new down pipe with custom front pipe.. I believe TTS makes it. I think it retails for $400+ for the two peices, but its true 4" from turbo housing to 4 bolt flange. Its a pain in the rear to get to that down pipe on the duramax, but it can be done.

When I put an MBRP 5" exhaust on my Cummins it bolted right to the turbo outlet. From what I've noticed all the Duramax "Turbo back" exhausts don't mate to the Turbo but to the downpipe off the Turbo which is still a stock "restrictive" pipe.

Does any exhaust vendor make a 4" downpipe to use in conjunction with an MBRP or a Corsa system. I aslo noticed it might be a challenging proposition to get that pipe in place if there was one. Clearance looks real tight up against the firewall.

Any experience with this?

Mike

IMO I don't think there's a real advantage, unless your adding an aftermarket turbo.All aftermarket down pipes neck down for clearance issues.

I don't think a 4" pipe will fit without major mods to the firewall. The BD down pipe is 3.5" and fits with a minor firewall adjustment. It won't work on an LB7, but might work on an LLY or LBZ turbo.

Last I heard the TTS downpipe was on BO

Last I heard the TTS downpipe was on BO
When I inquired on the phone last week they had them. BTW, I was very impressed with the integrity of the TTS technical guy I spoke with (don't remember the name). He put it all out straight and simple. The Downpipe is a royal PIA to replace. Will there be a difference in performance?--- some, but given the basically stock setup I have, not enough to warrant the headache. I know I'll be buying my 4" system from TTS

I was inquiring at my local truck acessory shop about exhaust and I asked the same question. He stated that there are not many manufactures that make the down pipe, because they have the best made one already on it.

We were discussing my 05 duramax. He pushed the aluminized Bully Dog, cat back system. Pretty reasonable on the price also.

He pushed the aluminized Bully Dog, cat back system.

Not to bash Bullydog or anything but I have treid to install that same system on a friends truck twice now and both times it didn't fit. I can't remember the part number to it but it was a XC/SB truck and the system was just too long. I removed the stock catback system and loosely built the BullyDog system next to it to see what was going on and the lengths and bends in the intermidiate pipe were too long putting the over axle pipe hiiting the rear end. I tried to cut the intermediate pipe but you can't, the front of the pipe is swedged down to accept the four bolt flange that you have to cut off your stock pipe and the rear of the pipe is only six inches from a bend that you wont be able to mate to the muffler. To top it all off I called them and both times and was told the same thing, We make them to fit all truck types with the included extension pipe and it should fit. My friend returned it both times and he will probably go with a MBRP system as per my recommendation.
:rant: over.
Sorry for the long story but I want to share my experience for the crowd.

Don't some AM turbos come with a larger replacement down pipe?

TTS is the only one I know of sold separately though I don't see it listed separately on thier site I think they will sell it separately.

It might be a good thing to replace if you are dropping your transmission as that might make it easier to install.