🔧 G-Sport Catalytic Converters: Commonly Asked Questions

Choosing the right G-Sport by GESI catalytic converter can feel complex, especially with different generations, performance levels, and installation requirements to consider. To help make the process easier, we’ve put together answers to the most common questions about G-Sport converters — from horsepower ratings and CEL prevention to placement guidelines and emissions compliance. Use this FAQ section as a quick reference when selecting the best converter for your specific application.

Which G-Sport Catalytic Converter should I use for my specific horsepower or application?

Before selecting a size, it’s important to first determine which generation of G-Sport catalytic converter is right for your vehicle:

• GEN1 (300 CPSI): EPA-compliant and typically suitable for vehicles model year 2016 and older. Gen1 converters also typically prevent catalyst efficiency-related check engine lights (CELs) in these model years.
• GEN2 (400 CPSI): EPA-compliant and required to prevent catalyst efficiency-related CELs in vehicles 2017 and newer. Gen2 is compatible with all model years and is the preferred option when CEL avoidance is a priority.

Once the generation is selected, you can choose the correct converter size based on your power level:

• HO: 4" Diameter – rated up to 500 HP
• UHO: 4.5" Diameter – rated up to 850 HP
• UHO+: 5" Diameter – rated up to 1,000 HP (Gen2 only)
• UHOX: 6" Diameter – rated up to 1,200 HP (Gen2 only)

All G-Sport converters are engineered for high performance. The differences between models come down to horsepower handling capability and vehicle compatibility based on emissions system sensitivity.

What is the difference between GEN1 and GEN2 GSport converters (HO vs. UHO vs. Mid-Bed)?

G-Sport by GESI Catalytic Converters

G-Sport catalytic converters are available in two generations and multiple performance levels, making it easy to match your emissions requirements and horsepower goals with the right solution.

GEN1 vs. GEN2

• GEN1 (300 CPSI):
  • EPA-compliant and typically suitable for vehicles model year 2016 and older.
  • Designed to help prevent catalyst efficiency-related check engine lights (CELs) in earlier OBD systems.
• GEN2 (400 CPSI):
  • EPA-compliant and intended for 2017 and newer vehicles with advanced emissions monitoring.
  • Provides improved CEL prevention and greater compatibility with modern sensor strategies.

Performance Levels

• HO (High Output): 4" diameter – rated up to 500 HP
• UHO (Ultra High Output): 4.5" diameter – rated up to 850 HP
• UHO+: 5" diameter – rated up to 1,000 HP (Gen2 only)
• UHOX: 6" diameter – rated up to 1,200 HP (Gen2 only)

All G-Sport catalytic converters are performance-rated. The primary differences between models are horsepower capacity and emissions system compatibility.

What is a Mid-Bed Cat?

A Mid-Bed cat is a specific type of GEN2 catalytic converter that contains two separate catalyst bricks within a single housing, with an oxygen sensor port located between them. This mirrors the design commonly used in OEM catalytic converters.

The Mid-Bed option provides a high-performance, emissions-compliant replacement that maintains the physical and functional characteristics of factory systems—while offering GESI’s proven durability and flow performance.

Mid-Bed Converters are available in:

• 4.5" Diameter (UHO Mid-Bed)
• 5.0" Diameter (UHO+ Mid-Bed)

Each size is offered as either a substrate-only unit (no cones) or with 3" transition cones, giving fabricators multiple integration options.

Do G-Sport Catalytic Converters help with Check Engine Lights (CEL)?

G-Sport catalytic converters are engineered to meet EPA standards and are designed to work with factory oxygen sensor feedback systems. However, CEL behavior depends on the vehicle’s model year and the sensitivity of its emissions system:

• GEN2 (400 CPSI): Designed to prevent catalyst efficiency-related CELs, especially in 2017 and newer vehicles with advanced OBD monitoring.
• GEN1 (300 CPSI): Typically functions without triggering a CEL in vehicles 2016 and older, where post-cat O2 sensor thresholds are less aggressive.

For the highest likelihood of avoiding a CEL, the catalytic converter should be installed in the OEM location or as close to the original placement as possible. Placing the converter too far downstream may prevent it from reaching optimal operating temperature. Because catalytic converters require heat to effectively convert exhaust gases, cooler temperatures can reduce efficiency and increase the chance of triggering a fault code.

While our GEN2 converters greatly reduce the risk, no aftermarket converter can absolutely guarantee CEL prevention due to variations in factory calibration, sensor behavior, and vehicle condition.

Do G-Sport Catalytic Converters Meet CARB and Euro Emissions Standards?

G-Sport by GESI high-performance catalytic converters are designed to meet EPA emissions standards and are legal for use on federally registered vehicles outside of California and other CARB-regulated states. While our converters deliver excellent emissions performance, they are not CARB-certified and are not currently approved for use on emissions-controlled vehicles in California.

It’s also important to note that we offer four part numbers that are not EPA-compliant. These converters are listed under the OBD2 G-Sport Emissions Catalytic Converters category on our website and include:

• 10025
• 10030
• 12030
• 12230

These models are intended for custom and motorsport applications where emissions compliance is not required.

Regarding European standards, our GEN2 converters often meet or exceed the emissions performance thresholds defined under Euro 6 standards. We are currently working toward formal certification for use in European markets.

In summary:

• ✅ EPA-compliant (except for the part numbers listed above)
• ❌ Not CARB-certified (not legal for sale or use on public roads in California)

Can I mix different models (e.g., GEN1 + GEN2) in the same system?

In dual-bank systems, it’s important to use the same catalytic converter model on both banks to ensure balanced flow and consistent O2 sensor readings. Mixing different converter generations or sizes from one bank to another can cause uneven back pressure and may trigger a check engine light (CEL) due to inconsistent catalyst efficiency data.

That said, there are certain cases where using two different converter models within the same bank is acceptable:

• If your exhaust setup uses two catalytic converters per bank, you can run different models in the primary (monitored) and secondary (unmonitored) positions.
• For vehicles model year 2017 and newer, the primary converter should be Gen2 to help prevent catalyst efficiency-related CELs.
• The secondary converter, which is not monitored by the O2 sensors, can be a Gen1 — even on newer vehicles. This is a common configuration for customers looking to maximize flow while maintaining emissions compliance.
• Gen1 converters offer a slight flow advantage due to their lower 300 CPSI density, making them a good fit for secondary positions.

Summary:

• ❌ Do not mix models between banks in a dual-bank setup
• ✅ It is acceptable to mix models within the same bank if the primary converter is Gen2 on 2017+ vehicles

What is the recommended placement distance from the turbo or headers?

For optimal performance and emissions efficiency, G-Sport catalytic converters should be placed as close to the original factory location as possible. Proper placement is especially important for maintaining catalyst light-off temperatures and preventing check engine lights (CELs) related to catalyst efficiency.

Here are some general guidelines:

• Avoid placing the catalytic converter too far downstream, as cooler exhaust temperatures may reduce the converter’s ability to properly activate and maintain efficiency.
• If you’re building a custom system, aim to install the converter within 8–24 inches of the turbo outlet or header collector (or closer, if possible).
• For modern OBD2 vehicles, especially model year 2017 and newer, placement is critical — post-cat O2 sensors expect to see a specific temperature and reaction pattern, and moving the cat too far back can affect emissions readings.

All G-Sport converters are designed for durability, but correct placement ensures you get the most from your converter in terms of both performance and emissions compliance.