Opening up the stock exhaust? - Chevy and GMC Duramax Diesel Forum
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 11 (permalink) Old 08-23-2019, 06:41 AM Thread Starter
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Opening up the stock exhaust?

Couldn’t find anything on this so I’ll ask you guys. Has anybody found a easy way to open up/cut out/expand the factory tailpipe before it goes into the vented section. I’ve got a box of goodies laying in my garage to delete my truck but the local exhaust shop flat out lied to me and they can only bend up to 3” (they SAID they could make a delete pipe) I’ve figured out a fix for that but I’m stuck waiting a few more days for the pipe to show up. I was sniffing around under my truck last night and noticed that while the tail section is 4”, with the tip being 5”, the 4” necks down to 2.75” at the end. Without cutting the bugle off to get at it, how could one go about getting rid of that choke point? I’m going to borrow some pipe expanders from work and try to go in through the tip and flare it out, or try to do some very surgical sawzall work. Might cut the bugle off at the thin strips, cut the cone off and reweld the tip back on. My goal here is to open up the exhaust while leave as much stock stuff on as possible, so if I need to put it back stock in a hurry I can. Thoughts?

And no, I’m not just going to buy an aftermarket exhaust, I’m a tightwad to start with and this last round of hay almost every piece of equipment I own decided to break down in some new and exciting way so my play budget has been diverted to more important things

16 C.C. LT. Tinted, Weather Techs, Boost Tow mirrors, leveled on 35ish, Ridge Runner tuned
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post #2 of 11 (permalink) Old 08-31-2019, 12:52 PM
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I’m not sure why our exhaust pipe is reduced in diameter right before that vented section. It would require an additional process; which is one thing that makes me wonder if there’s some benefit involved, although I can’t imagine what that would be.

My idea would be to get the largest size hole saw I could that could pass thru the main exhaust pipe. I would make a long drill bit extension, which would give me enough length to reach up the larger tip and reach the main exhaust pipe. In my head, the hole saw would center itself (well enough, at least) on the OD of the main exhaust pipe to allow a slow RPM start with the drill. It would also be easy enough to create bushings for the drill extension to center the assembly in the extension, if needed. I’ve ran the scenario thru my head a few times, and don’t see why it couldn’t work...
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post #3 of 11 (permalink) Old 08-31-2019, 04:46 PM Thread Starter
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Ive been pondering on it and its just thin exhaust pipe, I think Im just going to go through the vents with a die grinder and burr (not sure the actual name) and eat the metal away. I was kinda shocked when I measured the outlet at 2.75.

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post #4 of 11 (permalink) Old 09-01-2019, 05:40 AM
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Exhaust necks now just before the slits to increase velocity and allow room for the cooler outside gases to get sucked in and mixed with the hot regeneration exhaust. I wondered about reaching up in there with a hole saw and just opening it up a little to help it breathe.

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post #5 of 11 (permalink) Old 09-01-2019, 08:22 AM
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I have some long extensions for my drill,think I'll attach a 3.5" hole saw and have at it.

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post #6 of 11 (permalink) Old 09-01-2019, 03:11 PM
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Quote:
Originally Posted by jlawles2 View Post
Exhaust necks now just before the slits to increase velocity and allow room for the cooler outside gases to get sucked in and mixed with the hot regeneration exhaust. I wondered about reaching up in there with a hole saw and just opening it up a little to help it breathe.
That was my guess as to why the outlet is the way that it is.
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post #7 of 11 (permalink) Old 09-02-2019, 05:54 PM
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should yeild ~1/2 HP on the dyno...

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post #8 of 11 (permalink) Old 09-03-2019, 10:28 AM Thread Starter
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Quote:
Originally Posted by Sandman_73 View Post
should yeild ~1/2 HP on the dyno...
People have spent good money on less

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post #9 of 11 (permalink) Old 09-03-2019, 07:42 PM
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People have spent good money and lost HP. (Just saying)

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post #10 of 11 (permalink) Old 09-04-2019, 05:02 AM
 
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Red face My Plan

The restriction on exhaust really bother me, it seem like really poor engineering from chevy, and reports of melted trailers was a big concern, so I had this idea.

I liked what banks did with exhaust but report of a lot of rust discourged me.

So I order a 4 inch 45 degree Stainless pipe from Summit racing for 45 dollars and painted black with high temp paint. Added a left over tip from another project, and a SS clamp.

I am going to cut off the the "trumpet" section right after the first bend and put this new pipe and tip. I still have to figure out a hanger strap to hold it up but don't think that will be a big problem.

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