Exhausts: Catted vs Catless

[boostedflatfour]

When people modify their exhaust system they have the option of completely replacing all of the catalytic converters with just piping or replacing them with one high flow catalytic converter.

How will you know which is best for you?

First of all the power difference between them is very minimal, probably somewhere around 3hp difference. I think the only time having a high flow cat will bottleneck your potential for power is when you are making 600+ horsepower on a racecar


Catless:
Pros- There are no catalytic converters in the way of your exhaust flow so your system will have the highest flow possible. Whether this is better for your car or not depends on the type of car. Some people will tell you that having no cats will give you a little bit better topend power.
Cons - There is no cat filtering your exhaust gases so it will smell more and also pollute the air more. When it comes to modifying cars most people do not care about polluting the air because it is bound to happen with high performance vehicles anyway. It can increase your chances of a cop pulling you over and checking out your mods because he can smell your catless setup. You also increase the risk of not passing emissions when your smog check comes around.


Catted:
Pros - Running a high flow cat on your car will give you a small amount of backpressure, and some engines will run better with a little backpressure. Small amounts of backpressure are usually associated with a little more mid-range torque. Most high flow cats will be advertised as being able to pass certain emissions so if you are worried about your future smog check you might want to stick with a high-flow cat
Cons - Exhaust systems with high-flow cats will always be more expensive than catless exhaust systems, usually ranging from $150-$200 more.


When it all comes down to it, people will pick their setup based on how much money they want to spend. So if you want to save some money so it can be used on some other part, go for a catless setup. If you are willing to spend a little extra money now and not have to worry about smog checks later pick up a catted setup

No matter which you choose, either setup will always perform better than your stock exhaust system.

[wred]

Very informative post. Here are some of my thoughts:
It is true that some cars will benefit from some backpressure; however, turbocharged cars in particular have all the backpressure anyone could want, and then some. It is my understanding that this is why, for turbocharged applications, any and all decreases in backpressure are a good thing.

The effectiveness (is that a word?) of a cat is dependent on its operating temps. The hotter a cat is, the better it does its job (to an extent, of course). This is why a cat that is placed closer to the block (or turbo, whatever) works better, because it gets hotter. But the downside... the closer a cat is to the block/turbo, the more restrictive it will be. It is up to the user to decide the balance between cat efficiency and power.

Technically, it is illegal to replace any OEM cat with an aftermarket one but in some states it is much easier to get away with one than others. NY and CA in particular are notoriously stringent on emissions laws, so their smog checks include a visual inspection, which you cannot pass unless it at least looks like your cats are stock.