The 6.7 Cummins diesel engine was introduced in 2007.5 as a replacement to the 5.9L due to tightening emissions regulations. Since then, emissions regulations have continued to tighten and various new systems have been added to the 6.7 Cummins. One of the reasons the old diesels remain so popular and expensive today is because they don’t have any of these modern emissions systems which tend to be problematic and very expensive to repair.
One of the new emissions systems added to the 6.7 Cummins is a diesel particulate filter, or DPF system. The DPF system has hung around since then and is still used in current Cummins engines.
While the diesel particulate filter and all the other emissions equipment is very good at reducing emissions, it also has its shortcomings. As we discussed in our 6.7 Cummins common problems guide, the DPF system is prone to clogging. Additionally, since it is part of the exhaust system it creates a lot of post-turbo backpressure which decreases turbo reliability and restricts performance. Lastly, when it does fail it costs about $2k-$3k to replace.
This guide is going to specifically cover the DPF system. We’ll discuss what the system is, how it reduces emissions, and the pros and cons of deleting the DPF system. If you want to read up on the various other systems, check out our guide on all 6.7 Cummins emissions systems.
What is a 6.7 Cummins DPF System?
DPF is a diesel particulate filter. Burning diesel fuel releases microscopic solid particles into the exhaust gas, commonly referred to as diesel particulates. These small, solid particles contain hundreds of different chemicals in them and are harmful to human health. The particulates can stick to your lungs and are carcinogens.
Diesel engines have oxidation catalysts, called DOCs, that function like normal catalytic converters. This helps clean exhaust gases, but it doesn’t capture these solid particulates. Enter the DPF, or diesel particulate filter.
DPF filters trap these particulates, commonly referred to as diesel soot. It looks like a catalytic converter and uses the same honeycomb internal structure but is made of ceramic materials. This honeycomb mesh structure captures the soot and then burns it into a harmless ash through a regeneration process.
Regeneration occurs in both passive and active cycles. When EGTs (exhaust gas temps) reach 950-degrees Fahrenheit or higher, the DPF soot naturally burns through passive regeneration. However, since exhaust gas temps don’t always get that hot, active regeneration needs to occur to clear out the filter. During active regeneration, diesel fuel is injected into the exhaust stream which heats up the exhaust gases as they pass through the DOC and then burns the DPF soot.
DPF System Changes
For 2007.5 through 2012 model years, the DPF system was separated from the DOC system. The DOC catalyst was integrated in the downpipe which was followed by the DPF piping. In 2013 the DOC was removed from the downpipe and integrated with the DPF filter.
Therefore, deleting a 2013+ DPF system will also delete the DOC. However, if you want to delete the DOC for 2012 or prior, you need to upgrade the 6.7 Cummins downpipe.
6.7 Cummins DPF Delete Benefits
There are two primary reasons for deleting the DPF system on the 6.7 Cummins. First is for performance purposes. Since the DPF system is part of the exhaust, it creates a lot of backpressure which detracts from performance potential. Secondly, the DPF system is prone to clogging and costs $2k+ to replace when it clogs.
- 15-30hp and 50-100wtq gains depending on your tune
- 2-5mpg improvements
- Less exhaust backpressure
- Improved turbo efficiency and reliability
- No more regen cycles
- Reduced maintenance and repair costs
Power gains and mpg improvements will vary depending on what year your 6.7 Cummins is and what tune you are running. If you don’t delete the DOC catalyst in the downpipe on older models then you likely will experience a lot less power gains since the DOC sits right behind the turbo.
The fuel mileage improvements come primarily from eliminating the need for active regeneration which shoots fuel directly into the exhaust stream. The other benefits are improved reliability from the turbo due to less backpressure and piece of mind knowing you aren’t going to clog your DPF and be out $2k-$3k in repair costs.
6.7 Cummins DPF Delete Cons
While deleting the DPF sounds good for the mileage and power gains, it isn’t all sunshine and rainbows. The EPA has been cracking down on emissions deletes so finding anyone to install one for you or work on your truck after its installed is becoming very difficult.
- Reduced resale value
- Must sell private party
- Voids factory warranty
- It is illegal
- Increases pollution and is harmful to the environment
- Requires a tuner
- Will fail inspections
The majority of the downsides of a DPF delete revolve around the fact that it is illegal. The dealership definitely won’t touch your truck and nowadays a lot of independent shops won’t be willing to work on it either.
Outside of the legality, it reduces resale value of your truck, is harmful to the environment, and requires a tuner which adds to the cost of deleting the system.
Should You Delete Your DPF System?
Honestly, unless you are chasing crazy power goals or using your truck purely for off-road applications then we don’t recommend deleting your DPF system. Some states will send your truck straight to the crusher if it’s caught with deleted emissions systems.
It creates so much more headache than necessary. If you want some power gains, drop an intake and tune on your 6.7 Cummins. Plus there are plenty of additional mods for the power hungry. Furthermore, you can get some nice MPG gains as well through a tuner and an intake,
I understand the cost of replacing the DPF if it clogs is scary, but a DPF delete isn’t going to be a ton cheaper. Also, Cummins has an 8yr 80,000 mile warranty on the DPF system.
Overall, it’s up to you and your willingness to put up with the headache of having an illegal car that no one will touch. But we just don’t think it’s necessary unless you are really trying to put down massive power numbers. These engines have already proved plenty capable with basic bolt-on mods.
How to Delete your 6.7 Cummins DPF
If you do need or want to delete your DPF system, there are a few components. First, you will need a DPF delete kit. Second, you will need a proper DPF delete tune.
While deleting these exhaust components mostly just requires bolting up some new piping, keep in mind that you won’t be able to find a shop to do it. You will need to either DIY a delete or pay someone under the table to do it as shops will not risk the potential fines.
DPF Delete Kits
As we mentioned above, 2013+ models have the DOC integrated into the DPF. Therefore deleting the DPF also deletes the DOC. For 2012 and earlier models the DOC has to be deleted separately, via an upgraded downpipe. If you want to maximize power gains and gas mileage, you’ll want to remove the oxidation catalyst in addition to the diesel particulate filter. Since the DOC bolts directly to the turbo, it is a lot more restrictive than the DPF system on pre-2013 engines.
Regardless of the year all DPF delete kits also delete the SCR system. The benefit of removing the selective catalytic reduction piping is that you no longer have to fill up on DEF fluid. Additionally, if you are going to remove one of these systems you might as well remove all of them.
A DPF delete kit is simply a straight pipe that replaces the stock DPF and SCR piping. There are turbo-back options for earlier models with the separated diesel oxidation catalyst.
A DPF Capable Tuner
The second necessary component for a DPF delete is a tuner. Only certain tuners can handle DPF deletes off the shelf so keep that in mind as you pick a tuner. While just about any tuner will work with a custom DPF delete tune, only a handful of devices come with pre-built off the shelf DPF tunes.
All these various emissions systems have numerous sensors and electronic components that send signals to the 6.7 Cummins ECM. Deleting the DPF system without a tuner will cause the engine to run extremely poorly. Additionally, reducing all the post-turbo backpressure without properly tuning boost levels can cause the turbo to over spin and fail.
The main point here is that while a $500 delete kit sounds cheap, keep in mind you will also need a tuner if you don’t have one which can add an extra $1,000 onto the delete cost. Here are the DPF delete capable tuners:
- EFI Live
- SCT X4
6.7 Cummins DPF Delete Summary
Overall, deleting the DPF and other emissions systems sounds like a really good idea. It prevents clogged filters, reduces maintenance costs, improves performance, and increases gas mileage.
However on the other hand it makes your truck illegal so that it won’t pass inspection, it hurts resale value, it’s bad for the environment, and most shops won’t touch your truck for repairs anymore.
So should you delete your 6.7 Cummins DPF system? We honestly don’t recommend it unless you really need to for extremely high performance applications. The DPF filter has an 8yr/80,000 mile warranty. And on top of that these trucks are still capable of producing power gains in excess of 200rwhp with all of the stock emissions systems still intact.
If you want to delete it for gas mileage purposes, you can also drop an intake and a tune onto the car for some MPG gains without hurting factory warranty or making your truck illegal. Again, it just creates way more hassle than it is worth unless you absolutely need it deleted for performance purposes.