EGR Delete: Is 51mm Right for Your TDI?

For many car enthusiasts and mechanics in the UK, the topic of Exhaust Gas Recirculation (EGR) valve deletion is a common one, particularly for those running VAG Group 1.9 TDI engines. The EGR system, while designed to reduce nitrogen oxide (NOx) emissions, often introduces a host of issues that can hinder engine performance and longevity. This leads many to consider an EGR delete, but a frequent question arises: should you opt for a 51mm EGR delete kit?

This article will delve into the intricacies of EGR deletes, helping you understand the benefits, the crucial differences in sizing, and the essential considerations before undertaking such a modification. We’ll explore why a 51mm kit might be suitable for your vehicle, compare it with other options, and discuss what to look for in a high-quality delete kit.

What is an EGR Delete and Why Consider It?

The EGR valve is an emissions control device that recirculates a portion of an engine's exhaust gas back into the engine cylinders. This process lowers combustion temperatures, thereby reducing NOx emissions. However, this recirculation of exhaust gases, which contain soot and carbon particles, can lead to significant build-up within the intake manifold, throttle body, and even the turbocharger. Over time, this carbon accumulation can restrict airflow, reduce engine efficiency, and potentially cause costly component failures.

The Performance and Longevity Benefits

By removing or blanking off the EGR valve, you effectively prevent these exhaust gases from re-entering your engine's intake system. This offers several compelling benefits:

• Reduced Inlet Air Temperatures: With no hot exhaust gas mixing with the fresh intake air, the air entering your engine is cooler and denser. Cooler air contains more oxygen, which is vital for efficient combustion, leading to potentially more power and improved throttle response.
• Prevents Inlet and Turbo from Clogging: This is arguably one of the most significant advantages. Eliminating the source of carbon build-up means your intake manifold, intake ports, and turbocharger vanes remain cleaner. This prevents performance degradation over time and extends the lifespan of these critical components, saving you significant maintenance costs in the long run.
• Improved Engine Efficiency: A cleaner intake path allows the engine to breathe more freely, leading to better combustion and potentially improved fuel economy, although this can vary depending on driving style and other modifications.
• Smoother Idling: Carbon build-up can sometimes lead to rough idling. An EGR delete can contribute to a smoother, more consistent engine idle.

For these reasons, many TDI owners view an EGR delete as a worthwhile modification for both performance and engine health.

Navigating EGR Delete Sizes: 51mm vs. 57mm

When considering an EGR delete, you'll encounter different pipe diameters, commonly 51mm and 57mm. The choice depends heavily on your specific engine code and intended use. It's crucial to select the correct size to ensure proper fitment and optimal performance.

When is a 51mm EGR Delete Suitable?

Based on expert recommendations, the 51mm EGR Delete is generally more suited to a wider range of 'most models' of 1.9 TDI engines. This often includes engines where the factory intake manifold and associated pipework are designed for a slightly smaller diameter, making the 51mm a direct and efficient replacement. If your primary goal is to simply remove the EGR valve and its associated issues without significantly altering other intake components, a 51mm kit is often the appropriate choice for standard or mildly tuned vehicles.

Understanding the 57mm Option

The 57mm (or 2.25-inch) EGR delete pipe is typically designed for applications where a larger diameter is beneficial for increased airflow. This size is specifically mentioned as being more suited to PD105 and PD150 engines. Furthermore, high-performance kits, such as the Darkside Developments Race Pipe, utilise a 57mm diameter to facilitate custom intercooler pipe setups, preventing hoses from slipping thanks to twin grooves. While the 57mm Darkside kit is specifically engineered for PD130 (ASZ), PD150 (ARL), and PD160 engines, demonstrating its suitability for more powerful PD variants, it can also be fitted to other 1.9 TDI engines when using a PD130/PD150 inlet manifold. For the 1.9 PD105, specifically, a 57mm delete should only be used if you intend to remove both the EGR Valve AND the Anti-Shudder Valve (ASV).

In essence, if you're looking for a general solution for many 1.9 TDI models, 51mm is a strong candidate. If you have a PD105, PD150, PD130, or PD160, or are planning more extensive performance modifications like custom intercooler setups, the 57mm option offers greater airflow potential and is often part of a more comprehensive performance package.

What Makes a Quality EGR Delete Kit?

Regardless of the size you choose, the quality of the EGR delete kit is paramount. A well-engineered kit ensures a perfect fit, durability, and reliable performance. Let's look at features exemplified by top-tier kits:

Precision Engineering and Materials

A superior EGR delete kit will be CNC machined from a single aluminium billet. This manufacturing process ensures extreme precision, eliminating weak points often found in welded components. A brushed aluminium finish not only looks aesthetically pleasing under the bonnet but also indicates a high standard of craftsmanship. Kits made in the UK, for instance, often adhere to rigorous quality controls, offering peace of mind regarding material integrity and fitment.

Innovative Design for Seamless Integration

Consider the design of the flange that bolts to the manifold. A unique design with countersunk bolt holes provides a neat, flush finish, allowing you to reuse the standard bolts rather than sourcing longer alternatives. This attention to detail simplifies installation and maintains a clean engine bay aesthetic.

Another key feature is the design of the boost gauge take-off. Some premium kits feature a unique grub screw design that allows for the neatest possible installation, eliminating bulky brass fittings. A tiny hole in this design can also negate the need for an 'in-line' reducer to prevent your boost gauge from fluttering under heavy load, providing a more stable and accurate reading. For those not utilising a boost take-off, this design ensures an exceptionally clean and uncluttered install.

Vehicle Compatibility: Is Your TDI Covered?

EGR delete kits are designed for specific engine codes. It's crucial to verify that the kit you choose is compatible with your vehicle. The 57mm Darkside Developments kit, for example, fits ALL VW / Audi / Seat and Skoda Vehicles with the PD130 (ASZ), PD150 (ARL) and PD160 Engines. Furthermore, it can be adapted for any other 1.9 TDI Engine when using a PD130/PD150 Inlet Manifold. Specific engine codes and models this kit fits include:

• VW Golf Mk4: ASZ 130, ARL 150
• VW Golf Mk5: BXF 90, BKC / BXE 105
• VW Golf Mk5 Plus: BXF 90, BKC / BXE 105
• VW Bora: ASZ 130, ARL 150
• VW Caddy: BJB 105
• VW Polo: ASZ / BLT 130
• VW Sharan: ASZ 130, AUY / BVK 115, BTB 150
• VW Jetta: BKC / BXE 105
• VW Passat: BKC / BXE 105
• VW Passat B5 / B5.5: AVF / AWX 130
• VW Transporter T5: AXC 85 & AXB 105
• Seat Leon: BXF 90, BKC / BXE 105, ASZ 130, ARL 150
• Seat Toledo: BKC / BJB / BXE 105, ASZ 130, ARL 150
• Seat Ibiza: ASZ / BLT 130, BUK / BPX 160 (Cupra)
• Seat Altea: BKC / BXE / BJB 105
• Seat Alhambra: AUY / BVK 115, ASZ 130 & BTB 150
• Audi A3 8L: ASZ 130
• Audi A3 8P: BKC / BXE / 105
• Audi A4: AVF / AWX 130
• Audi A6: AVF / AWX 130
• Skoda Fabia: BSW / 105, ASZ / BLT 130
• Skoda Octavia: BKC / BXE / BJB 105, ASZ 130
• Skoda Roomster: BSW 105
• Skoda Superb: AVF / AWX 130

Always double-check your engine code before purchasing any delete kit to ensure perfect compatibility.

Crucial Considerations: ECU Remapping and Legalities

One of the most important aspects of performing an EGR delete is the impact on your vehicle's Engine Control Unit (ECU). Once the EGR valve is removed or blanked off, the ECU will no longer receive a signal from it. This will inevitably cause the 'emissions workshop' light (or engine management light) to appear on your dashboard. To resolve this and prevent potential limp-mode issues, the vehicle's ECU will require reprogramming.

An ECU remap, or 'EGR delete software', will electronically tell the ECU that the EGR system is no longer present, preventing error codes and ensuring the engine runs optimally without the valve. This is a crucial step that should not be overlooked.

Furthermore, it is absolutely essential to understand the legal implications of removing emissions control devices. In the UK, it is illegal to use a vehicle on public roads if it has been modified in a way that affects its emissions control systems. Removing the EGR valve is considered such a modification. While an EGR delete can offer performance benefits, it also means your vehicle will no longer comply with emissions regulations. This could lead to issues during your annual MOT test, as well as potential legal repercussions if discovered on the public highway. Always ensure you comply with the rules and laws relating to your home country. Reputable suppliers explicitly state that they accept no responsibility for the use of this part on the public highway where removal of emissions controls is prohibited.

Deciding on an EGR Delete: A Summary Table

Frequently Asked Questions About EGR Deletes

What exactly is an EGR valve?

The EGR (Exhaust Gas Recirculation) valve is a component designed to reduce nitrogen oxide (NOx) emissions by recirculating a small portion of exhaust gases back into the engine's combustion chambers. This lowers combustion temperatures, which in turn reduces NOx formation.

Is an EGR delete legal in the UK?

No, removing or disabling the EGR system on a vehicle used on public roads in the UK is illegal. It constitutes tampering with emissions control equipment, which is a contravention of environmental regulations. Such modifications are intended for off-road or motorsport use only.

Will an EGR delete cause my car to fail its MOT?

Potentially, yes. MOT tests are increasingly scrutinising emissions control systems. While a visual check might not always identify a deleted EGR, the vehicle's emissions readings might be affected, and if the engine management light is on due to the EGR delete (without a proper remap), it will be an instant failure.

Do I need an ECU remap after an EGR delete?

Absolutely. Once the EGR valve is removed or blanked off, the ECU will detect its absence and register a fault code, illuminating the engine management light. Without a specific software delete (remap) for the EGR, your vehicle may enter 'limp mode' or suffer from performance issues. A professional remap is essential to properly integrate the delete and maintain optimal engine operation.

What's the main difference between a 51mm and 57mm EGR delete?

The main difference lies in the diameter of the replacement pipe, which affects airflow. A 51mm delete is generally suitable for a broader range of standard 1.9 TDI models. A 57mm delete, often found in performance-oriented kits, is designed for engines like the PD105 (when also removing the ASV), PD150, PD130, and PD160, or for custom setups requiring maximum airflow.

How do I know which size EGR delete I need?

The best way to determine the correct size is to identify your engine code. For most general 1.9 TDI applications, a 51mm might suffice. However, if you have a PD105, PD130, PD150, or PD160 engine, or are aiming for a high-performance setup, a 57mm kit (like the Darkside Developments Race Pipe) is likely the appropriate choice. Always consult with a reputable tuner or parts supplier, providing your exact vehicle details and engine code.

Conclusion

Choosing the right EGR delete kit, be it a 51mm or 57mm, is a decision that requires careful consideration of your engine type, performance goals, and, crucially, the legal landscape. While the benefits of preventing carbon build-up, improving airflow, and potentially gaining power are clear, the necessity of an ECU remap and the implications for road legality cannot be overstated. For those with PD130, PD150, or PD160 engines, or those looking to optimise airflow on a PD105 (with ASV delete), the robust 57mm kits, such as the precision-engineered options available, offer a compelling solution. Always ensure your chosen kit is compatible with your specific engine code and that you understand the full ramifications of such a modification before proceeding.

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