Catless Downpipe vs. High Flow Cat: The Main Differences

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A catalytic converter is an important part of your car’s exhaust system. It is a device that converts harmful gases into less harmful ones, which are then released into the atmosphere. 

The catless downpipe vs. high-flow cat debate is a hot topic in the automotive world. Catless downpipes allow engine exhaust to flow without any restrictions and rely on the high-flow catalytic converter for pollution control, while high-flow cats restrict engine exhaust to reduce noise and emissions. High-flow cats are required in some regions but not all, depending on local regulations.

What is a Catless Downpipe?

A catalytic converter is a device that converts harmful gases like nitrogen oxides (NOx) and carbon monoxide (CO) into less harmful substances. A catless downpipe is designed to replace the stock exhaust system on your car with an aftermarket one but without the catalytic converters. The absence of these converters can lead to higher levels of emissions in some conditions. 

What is a High Flow Cat?

High-flow cat converters are catalytic converters that have been modified to increase their airflow. These modifications include enlarged inlets, reduced internal diameter, and an increased number of honeycomb cells inside the converter. High-flow cats can provide an additional 10% – 20% more fuel efficiency than stock catalytic converters.

Catless Downpipe vs. High Flow Cat: Key Differences

ComparisonCatless downpipeHigh flow cat
Made of304 stainless steelPlatinum, Palladium, and Rhodium
FunctionCatalytic converters clean exhaust gases as they pass through a catalystIt is tasked with catalyzing the exhaust flow at a quicker pace
LegalNot legal in the USAYes
BenefitsIt helps mitigate the downside of having an exhaust system post-turboIt helps provide adequate processing for the exhaust that comes out
DisadvantagesA significant fume smell from the exhaustnot sacrifice effectiveness for greater efficiency
LouderCatless downpipes are always loudera tad bit louder for sure
PriceAround $150 and upAround $50 and up

Catless Downpipe Vs High Flow Cat: Major Differences

A downpipe is a connection of the exhaust pipe of an engine to the atmosphere. A high-flow cat is an emission control device that reduces emissions by changing the chemical composition of gases before they are released into the atmosphere. Catless Downpipes and High Flow Cats both have their pros and cons, but which one is right for you? I’ll break it down so you can make your decision more easily!

  • The catless downpipe is made of 304 stainless steel, which means it’s better for durability than the high-flow cats that are composed mostly of Platinum and Palladium.
  • The catless downpipe is like a bypass that lets the engine breathe easier. The high-flow catalytic converter on top of it speeds up its reaction time and makes sure all those pesky toxins are broken down into safe compounds before they get released back out again.
  • In the United States, it is not legal to install a catless downpipe though some countries do allow them. However, if you have high-flow cats installed on your vehicle and are traveling through certain states like California or Texas then these will be allowed by law but not all 50 plus.
  • The catless downpipe helps mitigate the downside of having an exhaust system post-turbo while high-flow cats provide adequate processing for this extra gaseous emissions.
  • The catless downpipe is a significant fume smell from the exhaust while high-flow cats do not sacrifice effectiveness for greater efficiency.
  • A catless downpipe is always louder while high-flow cats are a tad bit noisier for sure

Related: Oil Coming Out Of The Exhaust- Causes & what to do

FAQ Of Catless Downpipe

Is a Catless downpipe illegal?

It’s against the law in all states in the US and in Europe because cats pose a safety risk if they fall onto the road and cause an accident.

A catless downpipe is illegal for two reasons:

  • The lack of a catalytic converter also referred to as a “cat,” reduces the engine’s ability to clean itself and harms air quality by increasing tailpipe emissions.
  • If your car falls off an elevated ramp or gets launched by some other means, there is no protection stopping any animals from falling on the road. Cats don’t usually go near traffic-filled streets, but if one does happen to be there when your vehicle comes crashing down, it will easily get run over.

Is Catless downpipe bad for engines?

If you want to be a good steward of our environment, it is important that your downpipe does not have any catalysts.

3 Reasons Why You Should Get A New Catless Downpipe 

  • Pollution– The exhaust from combustion can pollute the air with harmful toxins like pollution and carbon dioxide.
  • Fuel Efficiency – Cats only make up about 10% of all emissions coming out when an engine operates but they contribute greatly
  • Even though cats may improve some power characteristics at high RPMs by helping reduce instability cats also cause tuning issues as we mentioned before so why would anyone opt for this if possible?

What are the benefits of a Catless downpipe?

Catless downpipes are commonly used for turbocharged cars to help mitigate the downside of having an exhaust system post-turbo. Catless downpipes are less restrictive than catalytic converters, so they can slam more air out of the engine compartment and produce higher top-end power without increasing backpressure as a traditional silicone muffler would. The extra flow has many benefits (including increased performance) but causes more drones on decel or at idle which some people don’t want or need.

Does a Catless downpipe add horsepower?

A downpipe is an aftermarket component that allows you to transport exhaust gas from your vehicle’s engine bay and away, usually in order for it not to interfere with performance. This means higher power because of better flow rates which allow turbomachinery to work more efficiently!

Will a Catless downpipe make my car louder?

Catless downpipes are always louder because they provide more space and less exhaust pressure for sound waves to travel. The result is a slightly bumped-up audio experience with increased performance, but much less bass than traditional setups due to cat-back systems like Header City Performance Exhaust Systems (HCPS).

FAQ Of High Flow Cat

Does high-flow cat increase performance?

Yes. Catalytic converters are designed to convert unburned hydrocarbons into carbon dioxide plus water vapor. A high-flow converter helps to maximize the efficiency of this conversion, which in turn increases performance (in the sense that more exhaust gasses are converted into fewer pollutants). 

Do high-flow cats make the exhaust louder?

The louder, the better. High-flow cats will be a tad bit noisier for sure but it all depends on what you find loud- from high-pitched growls to heavy barks and everything in between!

Are high-flow cats in California legal?

The California Air Resources Board has no high-flow cats that they are aware of. If someone were to install a new catalytic converter, it would have to come with the appropriate stickers or be an original equipment replacement part from Ford.

Will high-flow cats pass California emissions?

No, they won’t pass. The Solo units are installed in the stock location so there’s no need for them to be modified and installed at a later time when you’re ready for emissions testing- but that doesn’t mean we don’t make those modifications too! Our cars have been tested with all sorts of different parts from aftermarket headers up to full custom exhaust systems just like any other high-performance street machines out here today (and long ago).

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