What a Cummins delete kit removes and why owners install them

A delete kit for a 2018 Cummins diesel engine removes or bypasses emissions control systems — specifically the diesel particulate filter (DPF) and selective catalytic reduction (SCR) system. These systems trap soot and reduce nitrogen oxide emissions to meet federal environmental standards. Owners install delete kits to reduce engine backpressure, lower exhaust temperatures, and increase horsepower and fuel economy.

The 2018 Cummins 6.7L engine in Ram trucks comes with both systems factory-installed. A delete kit physically removes the DPF from the exhaust line and reprograms the engine computer to stop the SCR system from operating. The result is a cleaner, simpler exhaust path and an engine that no longer performs the regeneration cycles that periodically heat the exhaust to burn off trapped soot.

Owners report improved throttle response, cooler engine temperatures under load, and better fuel economy after deletion — though the exact gains depend on driving habits and how aggressively the engine is tuned afterward. Some also delete to avoid the cost of DPF cleaning or replacement, which can run $1,500 to $3,000 when the filter clogs.

Key Takeaways

  • A delete kit removes the DPF and disables the SCR system, which are emissions controls that reduce engine performance and create maintenance costs.
  • Installation requires both physical removal of the DPF from the exhaust and engine computer reprogramming to prevent fault codes.
  • Deleting emissions systems is illegal for on-road use in all 50 states under the Clean Air Act, though enforcement varies by region.
  • Off-road use in remote areas or on private land carries lower legal risk, but the vehicle cannot be registered or insured for street driving after deletion.
  • Common complications include check engine lights if the tune is incomplete, reduced resale value, and warranty voidance from the manufacturer.

The legal status of emissions deletion on 2018 Cummins trucks

Deleting emissions systems on any vehicle registered for road use is illegal under the Clean Air Act, which is enforced by the Environmental Protection Agency (EPA). The law applies to all 50 states and prohibits removing or disabling any component of the emissions control system. Violations can result in fines up to $37,500 per vehicle for the vehicle owner and up to $43,280 per vehicle for shops that perform the work.

Enforcement happens most often during emissions testing in states that require it — California, New York, Massachusetts, and several others. In those states, a deleted truck will fail the test and cannot be registered. In states without emissions testing, enforcement is less common but still possible through roadside inspections or if a vehicle is impounded for other reasons.

The legal distinction between on-road and off-road use is important. A truck used only on private land, in remote areas, or in competition is at lower legal risk, though technically the law still applies. Once a vehicle is deleted, it cannot be legally registered for street use, and insurance companies may deny coverage if they discover the modification.

What's included in a typical 2018 Cummins delete kit

A complete delete kit for the 2018 Cummins 6.7L includes a DPF delete pipe (a straight exhaust tube that bypasses the filter), an SCR delete tune (engine computer reprogramming), and sometimes a DEF delete (which disables the diesel exhaust fluid injection system). Some kits also include a new exhaust manifold gasket, clamps, and hangers to fit the new piping.

The DPF delete pipe is usually mandrel-bent stainless steel or aluminized steel and bolts directly into the factory exhaust flanges where the DPF was mounted. The SCR delete tune is a file loaded into the engine's PCM (powertrain control module) that removes all emissions-related fault codes and prevents the engine from trying to operate systems that are no longer there.

Kits vary in quality and completeness. Budget kits ($400 to $800) may include only the pipe and a basic tune. Mid-range kits ($800 to $1,500) add better piping materials and more thorough tuning. High-end kits ($1,500 to $2,500) often include custom tuning, additional performance enhancements, and support from the tuner if problems arise.

Installation steps and what to expect

Installing a delete kit requires both mechanical work and computer tuning. The mechanical part involves lifting the truck, removing the factory DPF assembly (which is bolted to the exhaust manifold and the muffler), and installing the delete pipe in its place. This typically takes 2 to 4 hours for someone experienced with exhaust work and may take longer if rust or seized bolts are encountered.

The computer tuning is done by connecting a laptop or handheld tuner to the OBD-II port under the dashboard. The tuner reads the current engine file, loads the delete tune, and writes it back to the PCM. This step takes 30 minutes to an hour and is often done while the truck is on a lift so the exhaust work can be completed at the same time.

Most owners either have the work done at a diesel performance shop (which charges $1,200 to $2,500 for labor plus kit cost) or do the mechanical work themselves and send the tuning to a remote tuner via mail-in service. Mail-in tuning is cheaper ($200 to $500) but requires the owner to remove and reinstall the PCM themselves or have a local shop do just that step.

Common problems after deletion and how to avoid them

The most frequent issue is a check engine light that appears days or weeks after installation. This usually means the tune did not fully disable all emissions monitoring, and the engine is detecting that the DPF is no longer responding. A quality tune should prevent this, but incomplete or poorly written tunes sometimes miss certain fault codes. The fix is to contact the tuner and request a revised file.

Another common problem is reduced fuel economy in some cases, especially if the truck is driven aggressively after deletion. Without the backpressure of the DPF, the engine can run leaner than intended, and aggressive tuning can increase fuel consumption. Choosing a conservative tune and driving normally helps avoid this.

Warranty voidance is automatic — Cummins and Ram will not cover any engine or emissions-related repairs once deletion is discovered. Some shops will not service a deleted truck at all. Resale value also drops significantly because the next owner inherits the legal liability and cannot register the truck in emissions-testing states.

To minimize problems, use a reputable tuner with references, choose a quality DPF delete pipe (not the cheapest option), and have the work done by someone familiar with 2018 Cummins trucks specifically. Avoid aggressive tuning if the truck will be driven on public roads, and keep records of what was done in case you ever need to explain the modification to a mechanic or inspector.

Alternatives to full deletion if you want better performance

If you want improved performance without the legal and warranty risks of full deletion, several alternatives exist. A DPF cleaning service removes built-up soot without removing the filter, restoring some lost performance and reducing regeneration cycles. This costs $500 to $1,500 and is legal, though it is temporary — the filter will clog again over time.

A performance tune that keeps emissions systems active can add 20 to 40 horsepower and improve fuel economy by 2 to 4 miles per gallon without disabling the DPF or SCR. These tunes optimize fuel injection timing and boost pressure while leaving all emissions hardware in place. They cost $400 to $800 and are legal for off-road use; on-road legality is a gray area that varies by state.

Upgrading the intake and exhaust (adding a cold-air intake and a cat-back exhaust system) also improves airflow and can add 10 to 20 horsepower. These modifications are legal in most states as long as the catalytic converter and muffler remain in place. Combined with a mild tune, they provide noticeable gains without the risk of deletion.

Frequently Asked Questions

Will a delete kit make my 2018 Cummins fail emissions testing?

Yes, it will fail in any state that requires emissions testing. The test checks for the DPF and SCR systems, and a deleted truck will not have them. In states without emissions testing, you will not encounter this problem during registration, but the vehicle is still illegal to drive on public roads.

Can I delete my truck and then re-install the DPF later to pass inspection?

Technically yes, but it is difficult and expensive. The DPF itself cannot be reinstalled once removed, but a new one can be purchased and installed. The bigger problem is the tune — reversing a delete tune requires the original factory file, which is hard to obtain. Most tuners do not keep records of factory files, so you may not be able to restore the truck to stock condition.

How much horsepower does a delete kit actually add?

A delete kit alone (just the pipe and basic tune) typically adds 30 to 50 horsepower. More aggressive tuning can push this to 75 to 100 horsepower, but at the cost of higher fuel consumption and engine stress. The exact gain depends on the tune, the truck's condition, and how it is driven after installation.

Will my insurance cover a deleted truck?

Most insurance companies will not knowingly insure a deleted truck, and many policies specifically exclude coverage for illegal modifications. If you delete your truck, inform your insurance company — they may drop you or charge a higher premium. If you do not disclose the deletion and file a claim, the company may deny coverage when they discover it during inspection.

Is it worth deleting my truck if I plan to sell it later?

Probably not. A deleted truck is worth $2,000 to $5,000 less than a stock truck, depending on the market and the buyer's location. Buyers in emissions-testing states will not touch it. You also lose the remaining factory warranty, which can be worth $3,000 to $5,000 on a newer truck. Deletion makes sense only if you plan to keep the truck for many years and use it primarily off-road.