Also available in: 3.000" Inlet/Outlet (85032) | UHO Core 6-Pack (685002)
850HP OF EPA-COMPLIANT FLOW FOR BIG-BORE EXHAUST SYSTEMS — G-SPORT GEN1 ADVANCED UHO
The G-Sport Gen1 Advanced UHO (Ultra High Output) Catalytic Converter (85042) is the largest inlet/outlet in the Gen1 line: a full 4.000" inlet/outlet for big-bore single-turbo and high-displacement systems on 1996–2016 OBD1/OBD2 vehicles, 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 GEN1 Advanced series pairs GESi's proven S-Wound metallic substrate in a 300 CPSI cell count with their proprietary precious-metal wash coat. The lower cell density gives Gen1 a slight flow advantage over the 400 CPSI Gen2, and it typically keeps catalyst-efficiency check engine lights off on 2016-and-older OBD systems. Building a 2017 or newer vehicle? Use the Gen2 UHO 4.000" (85240) instead — its coating is engineered for the tighter monitoring on those platforms.
FEATURES
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Rated up to 850hp per converter — 4.500" body, full 4.000" inlet/outlet
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300 CPSI S-Wound metallic substrate — thinner cell walls than ceramic and a lower cell density for maximum flow
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Proprietary precious-metal wash coat tuned for 1996–2016 OBD emissions monitoring
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Nickel-lined, furnace-brazed core with Double-Lock canning — the substrate cannot telescope or fail under boost
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300 Series stainless steel construction inside and out; withstands spikes up to 1,600°F
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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: 300 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: 3.41 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 Gen1 UHO 4.000" for builds between 500hp and 850hp per exhaust bank on 1996–2016 vehicles running 4.000" tubing. Past 850hp, the Gen2-only UHO+ 5.000" core (85500, 1,000hp) and UHOX 6.000" core (85600, 1,200hp) are compatible with all model years. Gen1's extra flow also makes it the recommended choice for the unmonitored secondary position in two-converter-per-bank systems — even on 2017+ vehicles with a Gen2 primary.
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.
