The catalytic converter (also called “cat”) is an important component of your vehicle’s exhaust system that is designed to reduce harmful and toxic gases that are byproducts of your engine.
A common question that we come across online is can you actually drive a car without a catalytic converter?
While we do have a very straightforward answer to this, driving without a catalytic converter is more of a “should you do it?” instead of a “can you do it?” kind of topic.
Can you drive a vehicle without a catalytic converter?
Generally, removing a catalytic converter will not cause direct damage to the engine or exhaust components, thus, the car’s ability to run remains unaffected for the most part.
However, it is illegal in many places to remove the catalytic converter, as it is required to pass emissions tests.
How does a catalytic converter work?
The catalytic converter got its name because it contains “catalysts” inside it that “convert” exhaust gasses into less harmful byproducts.
Such catalysts are usually a combination of rare metals like platinum (Pt), palladium (Pd), and rhodium (Rh) that all coat the honeycomb-like interior of a catalytic converter when opened up.
There are two main types of catalysts in a catalytic converter that have their own role to play in the conversion of toxic gasses, namely the “reduction catalyst” and the “oxidation catalyst”.
Reduction Catalyst
The reduction catalyst is one of two important catalysts inside a converter, and its role is to trigger a chemical reaction with pollutants called nitrogen oxides.
Through this reaction, the catalyst basically separates the nitrogen oxide molecules into nitrogen and oxygen atoms without undergoing any changes to itself.
In turn, this will allow the formation of separate nitrogen and oxygen gases, which are harmless at this point since they naturally occur in the air we breathe.
The nitrogen atoms then attach to the reduction catalyst, while the oxygen passes through the converter and out the exhaust.
Oxidation Catalyst
The second type of catalyst is in charge of the oxidation process, which helps reduce both hydrocarbons (HC) and carbon monoxide (CO) by adding oxygen.
This is done by burning the two pollutants, thereby turning them into carbon dioxide (CO2) and water vapor, which are less harmful byproducts.
Where is the catalytic converter located?
The exact location of the catalytic converter may slightly vary for each car, but generally, it will be at the front of the exhaust system just before the exhaust manifold (or headers).
The catalytic converter will look similar to a muffler because of its cylindrical shape, and it will usually have two of several O2 (oxygen) sensors installed on your car before and after it.
Catalytic converters also commonly come with a heat shield, which can range from completely enclosing them (1st diagram), or simply covering the area around them (2nd image).
In other cases, the catalytic converter is integrated into the exhaust manifold itself.
This setup is more commonly used in modern cars as it allows the catalytic converter to get up to operating temperature faster, thereby increasing its efficiency.
An example of this kind of setup would be Honda’s R-series engine, which puts the catalytic converter right at the front of the engine together with the exhaust manifold.
What happens when you drive without a catalytic converter?
All in all, the biggest downside to removing your catalytic converter is that it will create more harmful emissions, thus making your car more likely to fail tests and be illegal to drive.
But despite this and our mentioning that the engine wouldn’t really get damaged just by doing it, there are still other things to keep in mind whenever you do remove your catalytic converter.
Fuel Economy and Performance
Catalytic converters are restrictive by nature, especially when it comes to getting the most optimum performance out of your engine.
While it’s pretty common to get some power gains by removing the catalytic converter, tuning is also usually performed alongside this to accommodate this change.
However, if you are simply going to remove the catalytic converter, the performance gains will just be minimal, if any at all, for the average car.
As far as fuel economy goes, there has been a bit of a debate going on if removing the converter actually improves or worsens it, which may also be dependent on the exact car.
Anecdotal evidence suggests that some people do experience worse fuel economy after removing the catalytic converter, and the most common cause actually does make sense.
We’ve mentioned that the catalytic converter contains two of several O2 sensors that your car has (one before and one after the converter).
Thus, removing the converter will cause the O2 sensors to have faulty readings, which in turn makes the engine use up and burn more fuel to compensate.
Engine Light
This one is somewhat connected to the previous consideration we’ve discussed, as it also involves the O2 sensors.
Whenever you remove the catalytic converter and replace it with just a straight pipe, the second O2 sensor after the converter will read the same as the first one before the converter.
This second O2 sensor, which is also called the “downstream/lambda” sensor, will then trigger a fault code that turns on your “check engine light”.
This is because the O2 sensor thinks that there is something different about the catalytic converter’s usual efficiency.
As a result, the data sent by the O2 sensor to the ECU (electronic/engine control unit) is different from the usual data, thus causing the check engine light to come on.
With a faulty code like this, it will be a lot harder to track actual problems when they come about unless you manage to turn the check engine light off.
Once again, finding a way around this while also maintaining performance and some amount of fuel economy will be down to some form of ECU tuning.
Exhaust Noise
Now, this consideration can be both a pro and a con depending on your preference for the sound that your exhaust makes.
Generally, the catalytic converter also gives some amount of muffling effect similar to resonators, mufflers, and any other form of exhaust silencer.
When it comes to running a car with a missing catalytic converter and no pipe to link the two open ends, it will be significantly louder and may even cause droning and vibration in the car.
However, replacing it with a straight pipe while still keeping the other factory silencers (e.g. resonators and mufflers) in place will still change the sound but not by much.
Exhaust Smell
Removing the catalytic converter will obviously remove the very thing that is reducing the toxic emissions in the first place.
With the catalytic converter removed, all of the exhaust fumes that should have been cleaned by the catalysts now start to give off a bad smell that can find its way into your car’s cabin.
So not only are they bad for the environment, but it’s also bad for anyone that manages to inhale the fumes.
Failing Vehicle Safety Inspection
Aside from the emissions test itself, which specifically tests the emissions of your car’s exhaust system, there is a vehicle safety inspection that you also need to pass.
This inspection is separate from the emissions test in most US states, and will comprehensively assess various components of your car, including its exhaust system.
More than likely, you will fail the vehicle safety inspection in a lot of states by having the catalytic converter removed, as all mandated safety and emissions equipment need to stay on the car.
This is assuming that your car wasn’t made before 1975, however, which was the year when all vehicles in the US were required to have a catalytic converter.
Otherwise, it will depend on the state whether or not cars older than 1975 that weren’t fitted with catalytic converters from the factory can pass inspection.
Is it safe to drive with a bad catalytic converter?
Catalytic converters are generally manufactured to last the lifespan of the vehicle itself, but this isn’t always the case, unfortunately.
As exhaust gases repeatedly enter and exit the honeycomb-like interior of the converter, there will naturally be a build-up of residue over time.
When too much residue builds up within the converter’s honeycomb structure, it could get clogged and impede the natural flow of the exhaust gasses.
By the time the catalytic converter gets clogged, it will render even the reaction-resistant catalysts inside useless.
Sure, it’s still possible and not too bad to drive with a clogged or damaged catalytic converter, but we have listed some symptoms below that you can definitely still feel if you don’t replace it.
Symptoms of a Bad Catalytic Converter
There are some tell-tale signs that your catalytic converter may not be working as it should, so you should definitely catch them earlier on before they cause even more issues.
Reduced Engine Performance
This may not come as a surprise anymore, as we’ve discussed earlier how the catalytic converter already restricts a certain amount of exhaust flow from the engine.
Further restricting the exhaust flow by having the catalytic converter get clogged can make the engine’s performance feel more sluggish than usual.
Reduced Fuel Economy
Having a bad catalytic converter not only impedes engine performance but also worsens your fuel economy in the process.
We’ve mentioned earlier how removing the converter can cause the O2 sensors to read incorrectly.
This can also happen with a bad catalytic converter, as the reduced airflow can signal the engine to burn more fuel, which further clogs the bad catalytic converter in the process.
Rotten Egg-like Smell
When a catalytic converter gets clogged or broken, it will not be able to convert the toxic chemicals the way that it should.
Since fuel also contains “sulfates”, which give off a characteristic rotten egg-like smell, not being able to convert them properly would mean that the smell will be a lot more noticeable.
Darker Exhaust Smoke
Another possible sign that your catalytic converter might be going bad is the smoke coming out of your exhaust appears darker.
Once again, this is connected to the fact that a broken or clogged catalytic converter will make it more difficult for the exhaust fumes to exit the exhaust system.
When the fumes eventually build up enough and come out, they will appear a lot darker and thicker than usual.
Why do catalytic converters get stolen?
If you haven’t been aware, cases of catalytic converter theft have been around for years, but there also has been a noticeable surge of them in more recent times.
Now, you might be wondering why thieves target the catalytic converter specifically out of all the vehicle’s components, and this is mainly because of the rare metals that they contain inside.
As we’ve discussed earlier, catalytic converters use platinum, palladium, and rhodium to make up the catalysts used in the converting process.
All three of these rare metals naturally sell for high prices when melted down and recovered.
Platinum, for instance, currently costs almost $1,000 per ounce of it, while palladium is around $1,800 for an ounce. Rhodium is the most expensive at a whopping $13,600 per ounce.
Just selling the catalytic converter itself to a recycler would pay around $50 to $250 depending on the car that it came from.
How to Protect Your Catalytic Converter from Being Stolen
Luckily, apart from having comprehensive auto insurance coverage, there are more preventive ways to protect your catalytic converter from being stolen.
Park in Well-Lit Areas
If you don’t have a closed garage or access to a secured parking space, then at least parking in well-lit areas where you can clearly see your car is your next best bet.
Install an Anti-Theft Shield
There are metal shields that you can buy for your catalytic converter, which are easy to install but difficult for thieves to remove because of their special security fasteners.
A good example of these kinds of anti-theft shields is the Cat Shield made by MillerCAT, although currently, it only has shields made for certain Toyota vehicles like the Prius.
Set Up a Motion-Sensing Light
If you park your car on your own open driveway overnight, you can consider installing an outdoor motion-sensing light on your driveway to deter possible thieves from your car.
Install a Dashcam
While it may be less effective in preventing the actual theft itself, installing a dashcam inside your vehicle that points towards the front and rear will be a big help in tracking down the thieves.
Additionally, you can also install a CCTV camera somewhere outside your house and point it towards your vehicle to get a better view of potential theft.
Get Your VIN or Plate Number Etched on the Catalytic Converter
Etching your VIN or license plate number on the catalytic converter itself will allow any recyclers or buyers to tell if it was stolen from somebody else’s vehicle easier.
