Also available in: 3.000" Inlet/Outlet (85230) | Fabricator 6-Pack (685240)
850HP OF EPA-COMPLIANT FLOW FOR BIG-BORE EXHAUST SYSTEMS — G-SPORT GEN2 ADVANCED UHO
The G-Sport Gen2 Advanced UHO (Ultra High Output) Catalytic Converter (85240) is the largest inlet/outlet in the Gen2 assembly line: a full 4.000" inlet/outlet for big-bore single-turbo and high-displacement systems, rated up to 850hp per converter (per exhaust bank). The 4.500" body keeps total substrate flow area comparable on paper to an open straight pipe, so the converter is not the restriction in the system.
The GEN2 Advanced series pairs GESi's proven S-Wound metallic substrate in a 400 CPSI cell count with their latest proprietary precious-metal coating, developed specifically for the advanced OBD monitoring strategies on 2017 and newer vehicles. That combination keeps catalyst-efficiency readings where modern post-cat O2 sensors expect them, preventing catalyst-related check engine lights on late-model platforms. Gen2 is also fully compatible with earlier model years, making it the safe choice when in doubt.
FEATURES
- Rated up to 850hp per converter — 4.500" body, full 4.000" inlet/outlet
- 400 CPSI S-Wound metallic substrate — thinner cell walls than ceramic mean more open flow area per cell
- Proprietary GEN2 precious-metal wash coat engineered for 2017 and newer emissions monitoring
- Nickel-lined, furnace-brazed core with Double-Lock canning — the substrate cannot telescope or fail under boost
- 300 Series stainless steel construction inside and out; withstands spikes up to 1,600°F
- EPA compliant — third-party lab tested (not CARB certified; not for use on emissions-controlled vehicles in California)
SPECIFICATIONS
- Inlet/Outlet: 4.000"
- Body Diameter: 4.500" OD
- Overall Length: 7.000" (±0.125")
- Cell Count: 400 CPSI
- HP Rating: up to 850hp per converter (per exhaust bank)
- Substrate: S-Wound metallic, furnace-brazed
- Material: 300 Series stainless steel
- EPA Compliant: Yes (not CARB certified)
- Weight: 3.73 lbs
- Connection: Welding Required
PERFORMANCE
In instrumented dyno testing with pressure probes upstream and downstream of the substrate, a properly sized G-Sport high-flow catalytic converter produced horsepower and torque curves identical to a straight pipe, with no measurable pressure drop across the core. Emissions reduction runs up to 99% for carbon monoxide, 98% for nitrogen oxides, and 95% for hydrocarbons.
APPLICATIONS & FITMENT
Choose the Gen2 UHO 4.000" for builds between 500hp and 850hp per exhaust bank running 4.000" tubing. Past 850hp, step up to the Gen2 UHO+ 5.000" core (85500, 1,000hp) or Gen2 UHOX 6.000" core (85600, 1,200hp). For 2016 and older vehicles, the Gen1 UHO 4.000" (85042) offers the same 850hp rating with a higher-flow 300 CPSI core.
For the full selection guide, see Understanding the G-Sport Catalytic Converter Lineup and our G-Sport FAQ.
INSTALLATION NOTES
This is a weld-in converter for 4.000" exhaust tubing. For best catalyst light-off and CEL prevention, install it as close to the OEM converter location as practical — on custom systems, within 8"–24" of the turbo outlet or header collector. In dual-bank systems, run the same converter model on both banks; mixing generations or sizes between banks can cause uneven backpressure and inconsistent O2 readings. Full best practices, common mistakes, and a pre-flight checklist are in our G-Sport Installation Guidelines.
Not sure which generation or output tier your build needs? Email us at support@aceraceparts.com with your platform, power goal, and tubing size and we will point you to the right part.