Want to unleash the hidden potential of your car? Upgrading your turbocharger can be a game-changer, but with so many options, choosing the right one can be overwhelming. This guide will explain what turbos do and how to pick the perfect fit for your car.

What's a Turbocharger?

Think of a turbo as a high-performance air pump for your engine. It forces more air into the engine, allowing for more efficient fuel burning and increased horsepower and torque (pulling power).

What is my stock turbo?

The guide can include a table listing the stock turbos for different WRX and STI models (2002-2008).

2002-2008 WRX TD04-13T

2004-2005 STI VF-39

2006-2007 STI VF-43

2008 STI VF-48

Aftermarket Turbos: Power Up Your Ride

Aftermarket turbos replace stock turbos to significantly increase engine performance. They achieve this by forcing more compressed air into the combustion chamber, resulting in more efficient fuel burning and ultimately, higher horsepower and torque.

Common Terminology

• Boost threshold: RPM at which positive pressure is generated in the intake system under maximum engine load.

• Turbo lag: The delay between pressing the accelerator and the turbo delivering full boost.

Selecting the Right Aftermarket Turbo

There's no one-size-fits-all turbo. Options fall into categories based on their performance characteristics:

• Increased Top-End Power: These turbos provide the most significant power gains at higher RPM ranges (e.g., VF30/VF34, 16G).

• Significantly Increased Top-End Power: Expect the most substantial power gains with these turbos, but they may experience more lag (e.g., VF22, 18G, 20G, FP Green).

• Quicker Spooling Turbos: Prioritize these for faster boost response with minimal lag. Ported and polished stock turbos fall into this category.

Factors to Consider When Choosing a Turbo

• Engine displacement: This affects the suitability of a particular turbo for your car.

• Compressor maps: These illustrate airflow at different pressure ratios, helping you choose the right turbo for your needs.

• Vendor and tuner recommendations: Seek advice from professionals familiar with your car and goals.

Common Turbo Upgrades

• Ported and Polished Stock Turbo: This is an easier upgrade that improves performance without major modifications.

Benefits of Aftermarket Turbos

• Increased horsepower and torque

• Improved acceleration

Drawbacks to Consider

• Requires supporting modifications (fuel injectors, fuel pump, engine management)

• Potential for boost creep if not properly managed

• Risk of engine damage if not installed or tuned correctly

Wastegate Upgrades: Managing Boost Pressure

Thinking about a wastegate upgrade? Here's what you need to know:

Wastegate upgrades come in two flavors, each solving a different problem:

• Higher Boost Threshold: Want more power? If your turbo has a low-pressure actuator, upgrading it can allow you to safely reach higher boost levels with a good boost controller.

• Boost Creep Prevention: If your car overboosts due to a free-flowing exhaust system, a larger wastegate flapper can help vent excess pressure and prevent "boost creep."

Here's a breakdown of the options:

• Upgraded Actuator: This allows for higher boost adjustments within its range (e.g., 15 psi actuator goes up to 24 psi). Race versions are also available.

• Larger Wastegate Flapper: This helps prevent boost creep by allowing more exhaust to vent. However, some turbos might require additional adjustments after this upgrade.

Considering an External Wastegate?

External wastegates are popular for a reason, but they're not for everyone. Here's what you need to know:

What it is: An external wastegate moves the wastegate venting to a separate location, allowing for more precise boost control.

The benefits:

• Stability for high-power setups: External wastegates offer more stable boost control compared to internal ones for extremely powerful cars (over 600 HP single turbo, 900+ HP twin turbo).

• More power (potentially): Precise boost control with externals can sometimes lead to slightly more power output.

The drawbacks:

• Cost: External wastegates are more expensive due to additional parts and custom piping.

• Complexity: Installation can be trickier on Subarus due to their design, requiring custom fabrication for the piping.

Conclusion

Aftermarket turbos offer significant performance gains but require careful selection, supporting modifications, and proper tuning for safe and reliable operation. Consulting with vendors and tuners is crucial to ensure the chosen.