Stealth DPF Delete by Flopster843

14 Nov 2011

I’d like to start this off by saying that tampering with or deleting the emissions equipment on any street legal vehicle could be considered illegal in most countries, including the United States. An emission delete is designed for off-highway or closed course competition use only.

There are two main parts to performing an emission system delete on a truck equipped with the 6.7L Cummins. The first part is removing the physical parts from the exhaust system. This can be accomplished by replacing the entire exhaust system with one that does not include the emissions, replacing the emissions part with a straight piece of pipe, or to punch out the interior of the OEM exhaust system.

The second part involves the vehicle’s computer. You can’t just remove the exhaust without modifying the computer, it will set a bunch of codes and you will no longer be able to drive the truck. You must delete the emissions equipment out of the truck’s computer with a programmer, or you can create simulators to fool the truck into thinking the system is still intact and functional. The home made sensors are very problematic and usually cause problems. Obviously, it is better to reprogram the truck so everything works properly.

I wasn’t going to destroy my perfectly good emissions system from my truck. So I acquired a complete exhaust system from a similar truck, and modified that one. The stock system starts with a Catalytic Converter (CAT) in the down pipe directly after the turbo, a Diesel Oxygenizing Catalyst (DOC), the Diesel Particulate Filter (DPF), and then a muffler.

I recommend starting this project by updating your computer with the correct DPF delete software. If you don’t install the correct software, you will set a bunch of codes and cause a lot of issues. Starting with the computer will ensure that you can update the computer correctly before you do all the physical work to change the exhaust. It would suck to get all of this done just to find out you can’t drive the truck because your programmer won’t work. Do not drive the truck with the delete software installed while the DPF is still intact. It will quickly plug the system and cause a lot of problems. I updated my Smarty with the “ME” software and uploaded it to my truck.

To start the physical modifications, I got a cheap hole saw kit from Harbor Freight to core out the exhaust system. The biggest hole saw you can get into the OEM exhaust is 3.5 inches. I welded a 3 foot steel rod to the pilot bit so I could reach all the way down through the exhaust system.

I bored out a 3.5 inch hole through the DOC and the DPF with the hole saw. I cut the hole until my saw bottomed out, removed the saw and then chipped out the center with a pry bar. Repeat this process several times until you have a hole all the way through both the DOC and the DPF. I then used the saw to skim down the sides and enlarge the hole to about 4.5 inches. The material in these pieces is extremely soft and the saw will make quick work of it.

The CAT in the downpipe is a different story. It is made of a very stout metallic substance. The hole saw won’t even start to punch a hole through it. I put a ½ inch drill bit in my pilot bit and drilled a ½ inch hole through the CAT. Then I had to utilize a pry bar to chisel out the remainder. You’ll have to peel it off layer by layer starting from the hole you just drilled. Eventually everything will come out, but it takes a long time.

Now that you’ve got the system punched out, you can install it on the truck or go a step further and paint it like I did. I went to the local parts store and bought 4 cans of VHT Flameproof ceramic header paint. Two cans of grey primer and two cans of black. I also got some red Scotch-Brite pads and some Acetone to clean everything with.

Start by sanding the exhaust system down to the bear metal to remove any and all contaminates that have accumulated over time. I used a sanding wheel in my 4 inch grinder to make quick work of it. I then finished the corners with a red Scotch-Brite pad. I didn’t sand the extension pipe because my truck is a short wheel base and doesn’t require that piece. After sanding, clean the entire thing with Acetone and paint like you would with normal spray cans. Do several light coats, not just one heavy coat. Follow the instructions on the cans and it should turn out nice.

VHT flameproof is rated to 2,000 degrees, but only after it is properly cured. It must be baked on by an oven, or by a very specific heat/cool cycle on the vehicle. The back of the can details this process quite well. Even after the paint is completely dry, it is very soft and scratches easily until this heat treating process is complied with. After that, it’s very robust.

The exhaust system I got had some old broken thermocouples left in it, so I cut the tips and the wires off of them and screwed them back into the exhaust to plug the holes. For the other empty bungs, I went down to the local ACE hardware and picked up some random stainless steel plugs. They’re not an exact fit, but they’re close enough to keep the exhaust from leaking.

Now that the new exhaust system is complete, it’s time to install it on the truck. Remove the spare tire before starting with the exhaust. This will give you more room to work with the tail section that must go up over the axle. Removal of the OEM system is fairly straight forward. Loosen the clamps and electrical connectors from each piece, and then remove the rubber hangar. Tug and pull until it comes off. Start from the back of the truck and take each piece off individually until you get to the downpipe. Leave the exhaust pressure sensor on the passenger side of the transmission attached to the transmission; just remove the rubber hoses coming from it.

Remove the clamp holding the downpipe to the turbo elbow and pull out the down pipe. Don’t remove the cast elbow from the turbo; you’ll just have to put it back on later. To remove the downpipe in one piece, you must drop the transmission cross member. Support the transmission with a jack, remove the three nuts holding the transmission mount to the cross member, then remove the cross member bolts and drop it down.

Install the new system in the exact opposite order that you removed the old. Start by hanging the downpipe on the rubber hanger on the bell housing. Then re-install the transmission cross member. Aligning the downpipe to the turbo is a pain in the butt, so stack some stuff on top of the cross member and set the downpipe on it to help get it aligned. Once you’ve got it aligned, install the clamp holding it to the turbo. Install the remaining exhaust one piece at a time working your way back. Then put your spare tire back under the truck.

Since the modified exhaust doesn’t utilize any of the OEM sensors, there are now several open electrical connectors hanging under the truck. To take care of this problem, I got in contact with James at Rollin Smoke Diesel (www.rollinsmokediesel.com) and got a set of DPF delete plugs. These are simply blank plugs that go into the OEM wiring harness to cap off the open connectors. Install these into the wiring harness and tie all of the wires up out of the way.

Start the truck after you ensure have got the correct software uploaded. Perform the proper heat/cool cycle listed on the back of the VHT cans to properly heat treat the ceramic paint on the exhaust. While you’re doing this, check for any leaks in the system. After the heat treatment process is complete, you’re finished with the install.

So how does it sound? Honestly, it sounds completely stock. There is no more noise, no more turbo whistle, no rumble, nothing. I’m actually pretty disappointed with it. I suppose leaving some material in the DOC and the DPF act as a muffler to dampen out all the sound. If you like your truck to remain quiet, then this is the mod for you. If you want it loud, this isn’t going to cut it. There’s a video of the exhaust on the “Media” page of CarboniteCummins.com that you can check out if you want. Pay special attention to the fact you can hear the engine and the dual disk clutch very clearly even though the camera is positioned right by the tail pipe.

Special Thanks To:

7642 N 400 W

Michigan City, IN 46360 219-851-1195

rollinsmokediesel@yahoo.com