Will Cutting Off Your Catalytic Converter Increase Horsepower?

In most modern cars, removing the catalytic converter produces little to no meaningful horsepower gain and often creates problems; on older or heavily modified engines, it can yield a small increase at high RPM. It is illegal on public roads in many countries, harms air quality, can trigger warning lights or drivability issues, and may cost you far more than any marginal performance benefit.

What the Catalytic Converter Does—and Why It Matters for Power

A catalytic converter cleans exhaust gases by converting harmful pollutants into less toxic emissions. It sits in the exhaust stream, so it does add some flow restriction. Decades ago, that restriction could noticeably sap power. Today’s converters are far more efficient and are engineered with low backpressure, especially on performance-oriented vehicles. On modern engines, the converter is integrated into how the engine management system controls fueling and ignition. Removing it changes exhaust dynamics only slightly but can disrupt sensor feedback, trigger fault codes, and force the ECU to run less optimally.

How Much Power Change to Expect, by Vehicle Type

The real-world power effect depends heavily on the vehicle, its age, and the state of tune. The following breakdown summarizes typical outcomes enthusiasts and dyno operators report.

• Modern stock gasoline engines (1996–present, OBD-II): Typically 0–2% change at wide-open throttle, often within dyno noise. Many see no measurable gain versus a healthy factory or high-flow converter.
• Modern turbocharged engines: Small gains (roughly 1–3%) possible at high load as the turbine sees slightly lower downstream pressure; however, tuned cars with a high-flow catted downpipe usually achieve similar results legally in many jurisdictions.
• Older carbureted or early fuel-injected engines (pre-1990s) with restrictive, early-generation converters: Potentially larger gains, sometimes 5–15 hp on big V8s, mainly at high RPM.
• Vehicles with a clogged or failing converter: Removing or replacing the faulty cat can “restore” significant lost power, but this is not a performance upgrade—it simply returns the engine to baseline when the converter is replaced properly.
• Track-only, high-output builds: Some builders use catless systems for maximum flow and heat management, but gains still depend on the broader exhaust and tune, not just the absence of a cat.

In short, the days when a cat delete reliably unleashed big power are largely past. With healthy, modern components, the converter is rarely the limiting factor.

Side Effects That Often Overshadow Any Power Gain

Beyond raw horsepower, cutting the converter has knock-on effects that can make the car worse to live with—and more expensive to keep on the road.

• Check Engine Light and readiness failures: Post-cat oxygen sensors monitor converter efficiency; removal usually throws codes (e.g., P0420/P0430) and causes emissions test failures.
• ECU behavior: Some vehicles alter fueling or catalyst warm-up strategies when faults are detected, potentially affecting drivability or even invoking reduced-power modes.
• Noise and odor: Exhaust becomes raspier and louder; unconverted hydrocarbons create a sharp, unpleasant smell. Leaks can raise carbon monoxide risk.
• Resale and insurer issues: Emissions tampering can lower resale value and complicate claims or inspections.
• Warranty and compliance: Tampering can void warranties related to the emissions system and fails inspections where testing is required.

These consequences are common, predictable, and—especially the legal and inspection issues—often more significant than any modest power change.

Legal and Environmental Realities

In the United States, removing or disabling a catalytic converter on a road-going vehicle is illegal under the Clean Air Act; similar prohibitions exist in Canada, the UK, and the EU. Many states and provinces conduct visual checks and OBD readiness tests—cat deletes typically fail both. Penalties vary but can include substantial fines, mandatory repairs, and registration suspension until the system is restored. There are exceptions for dedicated race or off-road vehicles that never use public roads, but those are narrow and heavily policed in some regions.

Environmentally, catalytic converters dramatically reduce carbon monoxide, hydrocarbons, and NOx. Deleting a cat significantly increases local air pollutants, especially in dense or enclosed areas.

Better Ways to Gain Power Without Breaking the Law

If your goal is stronger performance, there are legal, effective options that respect emissions rules and often deliver more consistent gains than a cat delete.

• Fix the bottleneck: If your cat is failing or clogged, replace it with an OE or certified high-flow unit; this restores lost power and keeps you compliant.
• High-flow, emissions-certified converters: Many aftermarket converters and catted downpipes carry regional certifications (e.g., CARB EO numbers) and offer improved flow with legal compliance.
• Cat-back exhaust: Improves sound and may reduce restriction after the converter; gains vary but are legal when emissions equipment remains intact.
• Intake and ECU calibration: A well-calibrated tune that retains emissions functionality can improve throttle response and midrange torque; ensure it’s certified where required.
• Maintenance basics: Fresh plugs, coils, filters, and addressing vacuum or boost leaks often unlock more real-world performance than exhaust changes alone.

These approaches typically yield more reliable improvements, preserve legality, and avoid the cascade of issues that follow a cat delete.

Is Your Catalytic Converter Actually the Problem?

Before blaming the converter for poor performance, look for common signs of a failing unit or run simple diagnostic checks.

• Symptoms of a clogged cat: Severe power loss at higher RPM, overheating under load, or a converter that glows red after driving.
• Rattling noises: Loose substrate can rattle, especially on startup and shutdown.
• Diagnostic codes: P0420/P0430 indicate low catalyst efficiency but don’t always mean a blockage; upstream sensor or exhaust leaks can trigger these too.
• Backpressure testing: A shop can measure exhaust backpressure or use upstream O2 readings to infer restriction under load.

Confirming the converter’s condition helps you avoid unnecessary or illegal modifications and target the real cause of lost performance.

Bottom Line

Cutting off your catalytic converter rarely provides a worthwhile horsepower increase on modern vehicles and brings significant legal, environmental, and practical downsides. If you’re chasing power, focus on maintenance, emissions-compliant exhaust parts, and reputable tuning; if your converter is truly the bottleneck, replace it with a certified high-flow unit rather than deleting it.

Summary

Removing a catalytic converter typically yields negligible gains on contemporary engines, can degrade drivability, triggers warning lights, and is illegal for road use in many regions. Older or heavily modified setups may see small high-RPM improvements, but better, legal alternatives—high-flow certified converters, cat-back systems, proper tuning, and maintenance—offer safer, more reliable performance without the legal and environmental costs.

Does removing a catalytic converter give more power?

Yes, removing a catalytic converter can increase power because it reduces exhaust backpressure, allowing the engine to “breathe” more freely, though the actual power gain varies and may be negated by negative consequences like poor engine control, a lit “check engine” light, and adverse effects on air quality. The engine’s computer may also attempt to compensate for the change, leading to even worse performance or fuel issues. 
Why Power May Increase

• Reduced Backpressure: Opens in new tabA catalytic converter restricts exhaust flow, and removing it allows exhaust gases to exit the engine faster, increasing horsepower. 
• Engine Efficiency: Opens in new tabAn engine functions as an air pump, and less resistance from the exhaust system means the engine can operate more efficiently and effectively. 

Why Power Might Not Increase (or could decrease)

• Engine Control Issues: Modern vehicles have engine control units (ECUs) that monitor and manage engine performance, including emissions components like the catalytic converter. 
• False Sensor Data: If a catalytic converter is removed, the oxygen sensors will send incorrect data to the ECU. 
• Poor Performance: The ECU’s response to these false readings can lead to a fuel mixture that is too rich or too lean, causing the engine to run poorly and potentially lose power. 
• Check Engine Light: A missing or compromised catalytic converter will trigger the “check engine” warning light. 

Other Consequences

• Increased Pollution: Catalytic converters are essential for reducing harmful emissions, so removing them will significantly increase your vehicle’s pollution. 
• Legal Issues: Tampering with or removing a catalytic converter is illegal in many places. 
• Engine Damage: An improperly controlled engine can overheat, knock, or suffer premature wear and tear. 

Is a car louder without a catalytic converter?

Yes, a car is significantly louder without a catalytic converter because the converter’s internal components reduce exhaust noise, and removing it allows more exhaust gases to flow freely, resulting in a louder, rumbling, or roaring sound. This increase in noise levels is a direct consequence of the converter’s primary functions: reducing harmful emissions and muffling engine sound. 
Why a Catalytic Converter Reduces Noise

• Muffling effect: The catalytic converter itself acts as a form of muffler, partially dampening the sound waves of the exhaust gases. 
• Exhaust flow restriction: The internal honeycomb structure of the converter creates a restriction, forcing the exhaust to pass through tiny passages. 

How Removing It Increases Noise

• Unrestricted flow: Without the converter, the exhaust gases can flow out with less resistance, leading to a much louder and often harsher sound. 
• Direct engine noise: The unsuppressed noise from the engine’s combustion process becomes more prominent. 

Consequences of Increased Noise

• Legal issues: The increased noise can violate local noise ordinances and lead to fines. 
• Hearing damage: Extremely loud exhaust can contribute to hearing damage. 
• Driver discomfort: A constant loud roar can be annoying and uncomfortable, especially on long drives. 

What happens if I cut off my catalytic converter?

Removing a catalytic converter makes a car louder and can potentially increase engine horsepower and fuel efficiency due to reduced exhaust back pressure, but it’s illegal in most places and can lead to significant problems. Without a catalytic converter, your vehicle will emit much more harmful pollution, your “Check Engine” light will likely come on, you may receive a hefty fine, and you could damage your engine over time from incorrect signals sent to the engine control unit (ECU).
 
Environmental and Legal Consequences

• Increased Emissions: The catalytic converter transforms harmful exhaust gases into less dangerous ones. Removing it allows these toxic fumes to be released directly into the atmosphere, polluting the air and causing health risks. 
• Illegal Operation: Removing a catalytic converter is illegal in many areas due to EPA regulations. You can face significant fines and penalties for operating a vehicle without one, and it will prevent you from passing emissions tests. 

Vehicle Performance and Health

• Engine Damage: Opens in new tabThe vehicle’s engine control unit (ECU) relies on data from oxygen sensors located before and after the catalytic converter. With the converter removed, the ECU receives incorrect readings, which can lead to the engine running too lean, causing high combustion temperatures that can damage engine components like pistons. 
• Illuminated Check Engine Light: Opens in new tabThe change in exhaust gas composition is detected by the oxygen sensors, triggering the “Check Engine” light on your dashboard. 
• Loudness and Noise Pollution: Opens in new tabCatalytic converters also act as a muffler, reducing exhaust noise. Removing one will make your car’s exhaust significantly louder, creating noise pollution and potentially disturbing neighbors. 

Potential Benefits (and Why They Aren’t Worth It)

• Increased Power/Better Gas Mileage: Opens in new tabSome argue that reduced exhaust back pressure could slightly increase horsepower and fuel efficiency. However, these potential gains are often negligible, especially on modern vehicles, and are outweighed by the negative consequences. 
• Engine Management Disruption: Opens in new tabModern vehicles are designed to work with a catalytic converter. Removing it disrupts the balance of the engine management system, which can negatively affect performance and may even lead to poorer fuel economy. 

How much HP can you gain from a cat delete?

A catalytic converter delete (cat delete) can add between 5-10 horsepower to a modern, factory-tuned vehicle, but gains vary significantly depending on the vehicle, whether it has a turbo (FI), if a tune is applied, and if the exhaust system has other supporting mods. While a cat delete offers little-to-no horsepower gain on a properly designed system, it can achieve higher gains on older, less restricted engines or heavily modified and tuned turbo vehicles, sometimes offering tens of additional horsepower with a proper tune.
 
Factors Influencing Horsepower Gains

• Vehicle Design: Modern cars are designed with catalytic converters in mind, so removing one often provides minimal gains. Older, pre-1996 vehicles with catalytic converters as an add-on may see significant improvements. 
• Engine Type: Naturally aspirated (NA) engines see smaller gains from a cat delete compared to forced-induction (FI) engines. 
• Tuning: A proper engine tune can maximize horsepower gains from a cat delete, as it calibrates the engine to work with the increased exhaust flow. 
• Exhaust Modifications: The overall efficiency of the exhaust system plays a role. Adding high-flow catalytic converters, which provide less restriction, can offer slight gains compared to a completely removed converter. 
• Supporting Mods: Gains are also dependent on other modifications, such as long-tube headers or specific intake upgrades. 

Potential Downsides

• Emissions and Legality: It is illegal in most areas and can result in substantial fines. 
• Engine and Sensory Issues: Removing the catalytic converter requires modifications to the sensors and potentially tricking the Engine Control Unit (ECU), which can lead to misfires or an unstable engine. 
• Health and Environment: Without the catalytic converter, the vehicle will emit a higher volume of toxic fumes, which can be irritating to the eyes and dangerous to the environment.