Deleting the Diesel Exhaust Fluid (DEF) system, also known as the Selective Catalytic Reduction (SCR) system, on a Cummins engine is a popular modification among diesel truck owners. This guide will walk you through the reasons for removal, potential risks, and important considerations.
Why Remove the Cummins DEF System?
The primary motivations for removing the DEF system are:
- Increased Power and Fuel Efficiency: The DEF system can restrict exhaust flow, potentially impacting engine performance. Removal can lead to slight gains in horsepower and fuel economy, although this can vary depending on the specific tune used after deletion.
- Reduced Maintenance Costs: The DEF system requires periodic fluid refills and occasional sensor replacements. Deleting the system eliminates these expenses. However, it’s crucial to factor in the potential cost of repairs if issues arise from the deletion.
- Elimination of DEF System Problems: DEF system components can malfunction, leading to costly repairs and downtime. While modern systems are generally reliable, deleting the system eliminates the possibility of these issues.
- Desire for a “Simpler” System: Some owners prefer a less complex engine setup and opt for deletion to remove the added components and electronics associated with the DEF system.
Potential Risks and Considerations
While removing the DEF system offers certain advantages, it’s essential to understand the potential drawbacks:
- Legality: Tampering with emissions systems is illegal in the United States and other regions. Deleting the DEF system can result in significant fines and potential legal repercussions if caught.
- Warranty Voidance: Removing the DEF system will likely void the manufacturer’s warranty on your Cummins engine. This means you’ll be responsible for any repair costs associated with the engine or emissions system.
- Environmental Impact: The DEF system is designed to reduce harmful NOx emissions. Removing it increases the environmental impact of your vehicle.
- Potential for Increased EGTs: Exhaust Gas Temperatures (EGTs) can rise after deleting the DEF system, especially under heavy load. Monitoring EGTs with a dedicated gauge is crucial to avoid engine damage. A stock truck generally doesn’t require an EGT probe due to factory safeguards, but deleting the DPF can alter this. Some argue that deleting the DPF disables some stock sensors, preventing the computer from maintaining safe operating ranges.
Monitoring EGTs After DEF Delete
As mentioned earlier, monitoring EGTs is crucial after deleting the DEF system. While opinions vary on the necessity of an EGT probe in a stock tuned truck, its importance increases significantly after a delete. When towing heavy loads or pushing the engine hard, high EGTs can cause significant engine damage. A pyrometer (EGT gauge) allows you to monitor these temperatures and adjust your driving accordingly.
Conclusion
Removing the Cummins DEF system is a complex decision with both benefits and drawbacks. While it can offer potential performance gains and reduced maintenance costs, it also carries significant legal and environmental risks. Carefully weigh these factors and consult with a qualified diesel mechanic before making a decision. Remember, ensuring your vehicle operates within legal and safe parameters is paramount.
