Exploring the Feasibility and Challenges of Adding Turbochargers at the Catalytic Converter's Exhaust

The concept of adding turbochargers at the end of the exhaust pipe, specifically after the catalytic converter, might seem innovative but faces significant practical challenges. This article explores the potential benefits, challenges, and why a traditional positioning upstream is often preferable.

Theory and Practicality

Technically, it is possible to install a turbocharger at the end of the exhaust system. However, this approach is not practical due to several engineering and performance issues:

Loss of Exhaust Energy: Turbochargers harness the energy in the exhaust gases to spin a turbine and compress incoming air. When placed after the catalytic converter, exhaust gases have already lost considerable energy, resulting in less effective turbine operation. Heat Management: Catalytic converters operate at high temperatures, which helps in reducing harmful emissions. Placing a turbocharger downstream would disrupt the heat balance, potentially causing overheating and damage to the turbocharger. Back Pressure: Proper exhaust flow is essential for optimal performance. Adding a turbocharger at the end of the exhaust system could increase back pressure, negatively affecting engine efficiency. Design and Integration: A custom exhaust system would be required, which involves significant redesign for mounting and effective air compression into the engine.

Alternative Options and Applications

Typically, turbochargers are positioned between the engine and the exhaust manifold, or before the catalytic converter along the exhaust path. This setup maximizes the energy from exhaust gases. However, some systems, particularly in front-mount or front-mid engine configurations, may benefit from rear-mounted turbos:

The Advantages:

Temperature Management: Rear-mounted turbos can operate in cooler conditions, reducing heat stress on components. Weight and Traction: Better weight distribution and improved traction can be achieved with rear-mounted turbos. Easier Packaging: Space at the rear of the vehicle can accommodate the turbos, along with intake systems that can harness higher ram pressure or air mass flow at higher speeds. Intercooling: Compressed air can be intercooled at the rear, helping to maintain optimal temperatures. Lower Back Pressure: Less exhaust back pressure provides better performance, especially in high-performance applications.

The Considerations:

The catalytic converter still requires hot exhaust to function effectively. With rear-mounted turbos, this can be addressed by using units capable of larger mass flow and proper honeycomb distribution. The issue of heat soak can be more easily managed with rear-mounted turbos as there is no underhood heat to contend with. While rear-mounted turbos can improve engine efficiency, the packaging challenge remains. It's crucial to have enough space at the rear to accommodate the turbo setup.

Conclusion

While rear-mounted turbochargers offer unique advantages, the engineering challenges and practical implications make it inefficient and impractical for most applications. Therefore, the conventional approach of placing turbochargers upstream of the catalytic converter remains the most effective strategy for optimal performance and reliability.

Key Takeaways:

Status Quo: Upstream placement is the standard and optimal location for turbochargers. Engineering Challenges: Placement after the catalytic converter would result in loss of exhaust energy, heat management issues, and increased back pressure. Performance Improvement: Rear-mounted turbos offer potential benefits but require careful consideration of space and engineering complexity.

This exploration highlights the importance of engineering principles in vehicle design and tuning, emphasizing the practicality of traditional placements while acknowledging the evolving landscape of performance engineering.