Duramax LML DPF Delete Guide

The Duramax LML got a few new emissions systems that the LMM didn’t have, most namely being the SCR system in conjunction with DEF fluid. Of course, many early model LML’s experienced SCR and DEF problems, resulting in expensive repair bills.

While the Duramax emissions systems are good for what they are meant to do (reduce emissions), they do have some downsides to both performance and reliability. For these reasons, deleting the Duramax LML DPF system is popular. This guide is going to discuss the various emissions systems, the pros and cons of deleting the DPF system, and what delete kits you’ll need to get the job done.

What is the Duramax LML DPF System?

DPF stands for diesel particulate filter. Diesel fuel doesn’t burn very cleanly which results in “particulates” being left in the exhaust gases. The DPF filter traps and burns these particulates before they enter the atmosphere via regeneration cycles.

The DPF system is actually the last part of the Duramax emissions components in the exhaust. First is the diesel oxidation catalyst, or DOC, which is essentially a catalytic converter. The DOC usually sits right behind the downpipe. Next up is the SCR (selective cat reduction) system which uses DEF fluid to turn NOx into gas and water vapors. The DOC and SCR systems burn the exhaust gas down as much as possible before reaching the DPF.

On the Duramax LML the DPF filter is actually integrated into the same piping and housing as the SCR system. So the exhaust system goes downpipe > DOC > SCR > DPF > cat-back exhaust and muffler.

An additional emissions system not mentioned is the EGR, or exhaust gas recirculation, system. This occurs before the air enters the exhaust system. It takes exhaust gases after they leave the combustion chamber and recirculates it back into the intake system so it can be burned again during the combustion process, further reducing emissions.

What Does a Delete Kit Remove?

A DPF delete kit is a bit confusing because it actually deletes more than just the DPF. It will remove the DOC, SCR, and DPF components. Since the DEF fluid is part of the SCR system it becomes irrelevant and is no longer needed.

• Diesel oxidation catalyst
• Selective cat reduction
• Diesel exhaust fluid
• Diesel particulate filter

Ultimately, it removes just about every emissions device except for the EGR system. If you want to delete the EGR too, check out our LML EGR Delete Guide.

A DPF delete kit is really just one piece of exhaust piping that bolts to the downpipe and the muffler. Therefore, it deletes all of the emissions system that sit within the exhaust.

What About EGR?

An LML delete kit does not remove the EGR system. The EGR system needs to be deleted separately. Deleting the EGR system requires plugging the EGR valve and replacing some hoses. There are also a number of other ancillary parts to this system such as an EGR cooler.

Ultimately, deleting the LML EGR requires separate delete kit.

EGR Delete Kit

Diesel Patriots sells an LML EGR delete kit separately. Additionally, they offer a complete delete package that includes DPF, EGR, and a tuner with free custom tuning. Since it usually makes sense to delete everything at the same time, a complete delete kit is the way to go and gives you everything you need.

Buy Here: LML Complete Delete Kit
Buy Here: LML EGR-Only Delete Kit

Benefits

• Possible 100hp+ power gains (mostly from a tune)
• 2-5mpg fuel economy improvements
• More efficient and reliable turbo
• Less backpressure in exhaust
• Lower EGTs
• No more regen cycles
• No more need for DEF fluid
• Better reliability and less potential repair costs

On a stock LML, deleting the DPF won’t really do much outside of improve reliability and help the engine breathe better. The gains or benefits from a performance perspective come from a tune and from when you are trying to really push your LML with additional mods and upgrades.

The other benefits are predominantly reliability related. Less backpressure means lower EGTs which means a healthier engine and turbo. Not having these expensive emissions pieces reduces the potential for them to fail, leaving you with a $5k repair bill. Lastly, you’ll save some money at the pump by seeing better gas mileage and not needing DEF fluid anymore.

Downsides

• Reduced resale value
• Lose all warranty and dealer won’t work on your truck
• Illegal and will fail emissions
• Must DIY the install and a lot of repairs
• Bad for the environment
• Must be used with a tuner

If you don’t care about the impact to the environment, the primary downside is the headache of dealing with having an illegal truck. With recent crackdowns, a lot of shops won’t touch deleted trucks and there certainly aren’t any that will install the deletes for you. You’ll lose any warranty which might not be an issue for the LML but you’ll also run into issues passing emissions testing which can be an issue.

The last point is that it is a bit more expensive than just buying a delete kit. You also need a delete-capable tuner which is going to run you another $500 or so.

Should You Delete the DPF System?

It makes a lot of sense for reliability, power potential, and saving some money on gas. However, the headache of dealing with a deleted truck can outweigh these benefits. Throwing a tune on your LML without deleting the DPF can create similar power gains. The emissions systems are only restrictive and need to be deleted when you’re upgrading the turbo and pushing big power levels.

Ultimately, we don’t recommend deleting emissions systems unless you are chasing crazy power levels, or your DPF/SCR has already failed. Deleting it after it has failed is no more challenging than deleting it before, so long as it doesn’t cause any additional engine problems.

How to Delete the Duramax LML DPF System

If deleting the DPF makes sense for you, or you don’t care and want to do it anyways, here’s how you do it. It requires two things:

1. Delete Kit
2. Tuner (capable of DPF deletes)

First off, you’ll need the delete kit which is simply just a portion of the exhaust system. You can either replace just the DPF section, or you can do a full turbo-back or downpipe-back exhaust. Secondly, you’ll need a tuner capable of handling the delete. Most name brand tuners are actually no longer capable, so we’ll provide a few recommendations below.

1) DPF Delete Kit

All of the emissions systems that get deleted sit in between the downpipe and the muffler. Using a simple delete kit will just replace the piping that has the DOC, DPF, and SCR. It should be a direct bolt on and not require any modification. It’s simply one pipe that replaces this whole section of the exhaust. These kits are usually about $300.

The second option is you can upgrade the full exhaust system from the downpipe and back. This will not only delete the DPF but will also allow you to upgrade the muffler and back (cat-back) portion of the exhaust. You can go a few routes here: either 4″ or 5″ exhaust piping. Additionally, you can choose straight pipe options for a louder exhaust note or get something with a muffler to keep it a bit more quiet. This can run from $500 up to $1,000 depending on what material you want and so on.

Best Delete Kit: Diesel Patriots LML Complete Delete Package

Diesel Patriots is one of the only brands left on the market still selling delete kits. They offer both individual DPF and EGR delete kits, and tuners with custom tuning and optional transmission tuning. Alternatively, they offer a complete kit that comes with all 3-in-1 to save you a little money. Since it makes sense to delete everything at the same time, this is the best route to go. The best part here is their tuners come with custom tuning…you won’t be able to find this anywhere else on the market.

Buy Here: LML DPF & EGR Delete w/Custom Tuning

2) DPF Delete Tuner

Tuning is required when the DPF is deleted since there are a number of sensors and things like that attached to the system. Additionally, you’ll need to have the regeneration cycles tuned out. Without a tuner your LML will go into limp mode and be pretty much undriveable.

Not all tuners are capable of handling deleted trucks. Unfortunately, the majority of the name brand tuners no longer support this.

• EZ Lynk 3 w/Custom Tuning & Optional Transmission Tuning

You might be able to find these tuners elsewhere on the market slightly cheaper, but they will not come with delete tunes or with custom delete tuning. This will require you to find a tuner who will make you a custom delete tune which is tough to find nowadays. Best bet is to purchase from Diesel Patriots above and get everything together.

Summary

The Duramax LML has 4 main emissions systems: the EGR, DOC, SCR, and DPF. An LML “DPF delete” will remove the DPF, DOC, and SCR. Additionally, it will eliminate the need for DEF as well. The only remaining emissions system on your GM truck will be the EGR system.

DPF systems are prone to clogging, and the SCR/DEF is already a common failure item on the LML. Therefore, deleting these systems can lead to more reliability and a lower likelihood for expensive repair bills. Additionally, these systems cause a lot of backpressure in the exhaust which is bad for the turbo and causes higher EGTs.

Deleting the DPF system will result in a healthier and more reliable engine. Additionally, while it doesn’t necessarily create a ton of power on the LML it drastically increases its power potential. Unfortunately, deleting the DPF has a number of downsides and implications. It is technically illegal and will make repairs, inspections, resale, and so on more challenging.

Deleting the LML DPF requires a delete kit and a tuner. Delete kits run from $300 for a base kit to up to $1,000 if you want to replace the full exhaust system. Adding a tuner is going to add another $900-$1,500 to the price tag. Therefore, a full delete is going to run somewhere between $1,200 and $2,500 depending on the route you go.