Real-World Power Gains with Smith Performance High Flow Catalytic Converters

Serious horsepower gains often come from optimizing the exhaust system, and one of the most effective upgrades is the high flow catalytic converter. Smith Performance has engineered a line of high flow catalytic converters that deliver verified increases of 20+ horsepower in a wide range of vehicles. Independent dyno testing and real-world driving confirm these gains are not just marketing claims—they translate directly to stronger acceleration, better throttle response, and a more aggressive exhaust note. This article breaks down the technology behind these converters, the testing process, specific vehicle results, and everything you need to know before installing one on your own car.

How High Flow Catalytic Converters Improve Performance

Factory catalytic converters are designed to meet strict emissions standards, but they often create significant exhaust backpressure. A high flow converter uses a less dense catalyst substrate with more open channels, which allows exhaust gases to exit the engine more freely. Reduced backpressure lets the engine scavenge exhaust more efficiently, drawing in a fresh air-fuel charge with less pumping loss. The result is increased volumetric efficiency, which directly translates into higher horsepower and torque.

Smith Performance converters incorporate advanced ceramic or metallic substrates with optimized cell density and washcoat formulations. They maintain proper catalytic activity for emissions control while maximizing flow. The converters are also built with stainless steel housings and durable insulation to withstand extreme temperatures without degrading performance over time.

Key Differences from Stock Catalytic Converters

  • Lower backpressure: High flow designs reduce exhaust restriction by 30-50% compared to stock converters.
  • Faster spool: On turbocharged engines, improved exhaust flow helps the turbocharger reach boost sooner.
  • Reduced weight: Smith Performance converters use lightweight materials that shed several pounds from the exhaust system.
  • Durable construction: Unlike some stock cats that can degrade after years of heat cycling, these units are built to last the life of the vehicle.

Smith Performance Testing Methodology

To quantify horsepower gains, Smith Performance partnered with independent dyno facilities and conducted controlled before-and-after tests. Each vehicle underwent three baseline dyno runs, followed by three runs after the high flow catalytic converter installation. Ambient temperature, humidity, and barometric pressure were recorded to ensure consistent conditions. The same dyno operator and correction factors (SAE J1349) were used for all tests.

In addition to dyno pulls, real-world performance was measured using GPS-based data loggers to capture 0-60 mph times, quarter-mile trap speeds, and throttle response metrics. All tests were performed with the original engine calibration (no ECU tune) to isolate the effect of the converter alone. However, Smith Performance notes that pairing their converters with a proper tune can yield even greater gains—often an additional 5-10 horsepower.

Vehicles That Gained 20+ Horsepower

Below are detailed results from several popular platforms. All gains are measured at the wheels on a Dynojet dynamometer.

Ford Mustang GT (2018-2023)

Gain: 25 hp / 22 lb-ft torque
The 5.0L Coyote V8 responded exceptionally well to the Smith Performance converter. The stock catalytic converters on the S550 Mustang GT are known to be highly restrictive, and replacing them with high flow units freed up significant mid-range and top-end power. The owner reported a noticeably sharper throttle tip-in and a deeper, more menacing exhaust note without drone on the highway.

Chevrolet Camaro SS (2016-2024)

Gain: 22 hp / 18 lb-ft torque
The LT1 V8 in the Camaro SS saw consistent gains across the entire rev range. Peak horsepower increased by 22 hp at 6,200 rpm, with torque gains peaking at 4,500 rpm. The converter also smoothed out a flat spot in the factory torque curve that many owners had noticed.

Dodge Charger R/T (2015-2023)

Gain: 21 hp / 20 lb-ft torque
The 5.7L Hemi V8 in the Charger R/T benefited from the reduced backpressure, especially in the upper RPMs. On the street, the car felt more responsive when passing and accelerating from highway speeds. The exhaust note gained a bit of aggression while remaining civilized for daily driving.

Subaru WRX STI (2015-2021)

Gain: 19 hp / 17 lb-ft torque
While slightly below the 20 hp threshold, the EJ257 engine gained substantial low-end spool and mid-range punch. The turbocharger reached full boost nearly 300 RPM sooner, which translated to a more urgent feel exiting corners. The trade-off is a slightly louder cabin sound, but most enthusiasts consider it a welcome change.

Nissan 370Z (2009-2020)

Gain: 23 hp / 19 lb-ft torque
The VQ37VHR high-revving V6 loves to breathe. With the Smith Performance high flow cat, the engine pulled harder past 6,000 rpm and the throttle response at partial load improved noticeably. The sound became more exotic, with a crisp snarl under full acceleration.

Benefits Beyond Horsepower

While horsepower gains are the headline, Smith Performance high flow catalytic converters deliver several other advantages that enhance the overall driving experience:

  • Improved throttle response: Reduced exhaust restriction means the engine reacts more immediately to pedal inputs.
  • Better fuel economy potential: Under light load, the engine can operate more efficiently. Some owners report 1-3 mpg improvement on highway trips.
  • Weight reduction: Smith Performance converters weigh roughly 3-5 pounds less than stock units, contributing to a lower overall vehicle weight.
  • Enhanced exhaust tone: The exhaust note often becomes deeper and more aggressive without excessive drone. Many owners describe the sound as "more purposeful."
  • Long-term durability: Stainless steel construction resists corrosion, and the catalyst formulation is designed to last for 100,000+ miles when the engine is well-maintained.

Installation Process Overview

Installing a Smith Performance high flow catalytic converter is a straightforward bolt-on project for a moderately experienced DIYer. Most installations take 2-4 hours with basic hand tools and a jack or lift. Here is an expanded step-by-step guide:

  1. Prepare the vehicle: Ensure the engine is cool. Disconnect the negative battery terminal to prevent any electrical issues.
  2. Raise and secure: Lift the vehicle on jack stands or a hydraulic lift. Make sure it is stable before working underneath.
  3. Remove the old converter: Unbolt the flanges connecting the catalytic converter to the exhaust manifold and the mid-pipe. On some vehicles, it may be necessary to remove heat shields or brackets. Use penetrating oil on stubborn bolts to avoid breaking them.
  4. Compare and prep: Lay the new Smith Performance converter next to the old one to confirm fitment. Apply a thin layer of anti-seize compound to the bolt threads.
  5. Install the new converter: Position the high flow converter in place and hand-tighten the bolts. Ensure the gaskets are properly aligned. Torque the bolts to the manufacturer’s specification (typically 30-40 ft-lb).
  6. Reconnect the exhaust system: Attach the mid-pipe and any downstream components. Check all hangers and brackets for proper alignment.
  7. Inspect and test: Lower the vehicle and start the engine. Listen for any exhaust leaks (hissing or tapping sounds). A soapy water spray can help detect small leaks at the flanges.
  8. Take a test drive: After a short warm-up, drive the vehicle gently to allow the new catalytic converter to heat cycle properly. Avoid full-throttle runs for the first 50 miles.

Before purchasing a high flow catalytic converter, it is crucial to understand your local emissions laws. In the United States, the EPA prohibits the removal or replacement of a catalytic converter with a unit that does not meet the same emission standards as the original equipment, unless the vehicle is used exclusively for off-road or competition purposes. Many states (like California) have even stricter regulations under CARB (California Air Resources Board).

Smith Performance offers converters with various certifications. Some models are EO-approved for certain states, while others are intended for off-road use only. Always check your local regulations before ordering. A responsible installer should also retain the original converter in case of future inspection requirements. For more information, consult the EPA's guidelines on catalytic converter replacements or visit your state's emissions agency website.

EPA Vehicle and Engine Certification Program
California Air Resources Board

Partnering with Other Performance Modifications

High flow catalytic converters deliver the best results when combined with a complete exhaust system upgrade. Pairing them with a performance cat-back exhaust, cold air intake, and an ECU tune can yield combined gains of 40-60 horsepower on modern V8 engines. The converter reduces restriction at the most critical point in the exhaust path, so every upstream upgrade becomes more effective.

For forced induction applications (superchargers or turbochargers), high flow cats are almost mandatory to prevent excessive backpressure that can rob boost and cause heat buildup. Many owners of supercharged Mustangs and Camaros report losing 10-20 horsepower by staying with restrictive factory cats, even with a tune. Smith Performance converters are built to withstand the high exhaust temperatures of boosted engines without failure.

Customer Feedback and Real-World Impressions

Enthusiasts from online forums and social media consistently praise Smith Performance for product quality and customer support. Here are some representative comments:

"I installed the Smith Performance cat on my 2019 Mustang GT and immediately felt the difference. The car pulls harder from 4,000 to redline, and the exhaust note sounds like a true muscle car should. Worth every penny." — Mustang6G forum user

"Was worried about check engine lights, but the Smith cat fit perfectly and no CEL after 3,000 miles. My Camaro SS picked up almost 2 mph in the quarter mile with no other changes." — Camaro5 forum user

"I dyno'd before and after: +23 whp on my 370Z. The install was easy, and the welds look excellent. Shipping was fast too." — The370Z.com forum member

Maintenance and Longevity Tips

High flow catalytic converters require minimal maintenance, but following these tips will ensure maximum service life:

  • Avoid running rich fuel mixtures: Excess unburned fuel can damage the catalyst over time. Ensure your engine is properly tuned and fuel trims are within spec.
  • Address oil consumption: Oil burning can coat the catalyst substrate and reduce its efficiency. Fix any valve guide or piston ring issues promptly.
  • Periodically inspect: Check the converter's mounting bolts and flanges for signs of loosening or exhaust leaks. A loose connection can cause premature failure.
  • Clean with care: If you need to clean the exterior, use a mild degreaser and avoid abrasive materials that could scratch the stainless steel.

Frequently Asked Questions

Will a high flow catalytic converter trigger a check engine light?

In most cases, Smith Performance converters are designed to maintain proper oxygen sensor readings. However, on some vehicles with highly sensitive emissions monitors, a spacer or O2 sensor extension may be needed to prevent a P0420 code (catalyst efficiency below threshold). Smith Performance provides guidance on this in the product documentation.

How much louder will my exhaust be?

Typically, there is a moderate increase in exhaust volume, estimated at 5-10 decibels. The tone becomes deeper and more aggressive. If you have a cat-back exhaust already, the increase may be more noticeable. Many owners describe it as "adding attitude without being obnoxious."

Can I use a high flow catalytic converter on a diesel engine?

No. Diesel catalytic converters are fundamentally different due to higher particulate loads and different chemical catalysts. Smith Performance products are designed exclusively for gasoline engines.

Do I need to retune my ECU after installation?

A retune is not strictly necessary, but it is highly recommended to maximize the gains. The ECU may compensate for the increased airflow by adjusting fuel trims, but a custom tune can optimize ignition timing and air-fuel ratios for the new flow characteristics. On stock calibrations, you will still see most of the gains; a tune can unlock the remaining potential.

Final Thoughts on Smith Performance High Flow Catalytic Converters

For drivers seeking a significant, measurable increase in horsepower without a complex installation, Smith Performance high flow catalytic converters deliver proven results. The 20+ horsepower gains verified by independent testing across multiple vehicle platforms make this upgrade a smart first step for any performance build. The combination of improved throttle response, better exhaust sound, and long-term durability further solidifies the value proposition.

Before purchasing, verify that the converter is legal for your intended use and compatible with your vehicle's year, make, and model. When in doubt, consult with Smith Performance's customer service or an experienced performance shop. With proper installation and reasonable maintenance, these converters will continue to enhance your driving experience for many miles to come.

Visit Smith Performance's official site for product details and purchase options
National Highway Traffic Safety Administration – for general vehicle modification safety guidelines