Can you benefit from running no cats on a tuned motor?

[Chizzychase]

Eventually I want to get my 5.3 tuned and I was wondering if there was a benefit of running no cats on your exhaust system? I know I would need dummy O2 sensors so my computer doesn't throw a code. I also know they make high flow cats as well would that be a better route to go? Just trying to get an idea of what would be better.

 

[gunslinger]

This has been discussed before and what I could gather in the other threads was basically this: Yes there would be a slight POTENTIAL for an increase due to the increase in airflow.

Now many people don't want to admit that because what you're doing would be illegal for street use and the tree huggers won't like it for the environment. Personally I am glad that cars have cats as the air quality was pretty bad before we did. Now I'm not going to get my undies in a twist over one more auto enthusiast gutting his exhaust, but some people do.

Now above I said you've got the potential for an increase, but you've got to tune it right. Some people just cut them and subsequently lose power (because the car is tuned for them on) but then they will argue that taking off cats will decrease your power. If no cats caused a decrease in power then dragsters and stock cars would be bolting on cats for HP gains but you don't see that.

In my opinion you will need to be really throwing a lot of HPs out before it would make a negligible difference. If you had 500+ horses then I'd say it may make a difference. Our cats are pretty high flow from what I've heard and I don't cutting them off is worth the smell for lets just say maybe 3hp.

You will defiantly notice the odor, and so will any chicks you take for a ride. They will however just think something is wrong with your car. My fiancee made a complaint about the smell of a truck we were behind (no cats). To me its not worth it for a street car, especially an SUV, but i've got straight pipes on the motorcycle and will on the gasser i'm building.

 

[sumo]

I deleted my rear o2 one is a dummy and the other side is where I put my wideband. I did headers and I went with a catted y section, even still they are small and still look to be high flow. I did cats because this is still a family ride and I didn't want to overpower everyone with fumes

 

[01ssreda4]

If youre gonna stay with stock manifolds dont bother. If going to long tube headers then by all means.

 

[Chizzychase]

If youre gonna stay with stock manifolds dont bother. If going to long tube headers then by all means.

Eventually I am going longtubes because i know I will see gains from them over the stock manifolds I will more then likely keep the cats on and if they go bad ill either take them out or run a set of high flow cats.

Its a daily driver and I don't wanna stink up the road

 

[Chizzychase]

This has been discussed before and what I could gather in the other threads was basically this: Yes there would be a slight POTENTIAL for an increase due to the increase in airflow.

Now many people don't want to admit that because what you're doing would be illegal for street use and the tree huggers won't like it for the environment. Personally I am glad that cars have cats as the air quality was pretty bad before we did. Now I'm not going to get my undies in a twist over one more auto enthusiast gutting his exhaust, but some people do.

Now above I said you've got the potential for an increase, but you've got to tune it right. Some people just cut them and subsequently lose power (because the car is tuned for them on) but then they will argue that taking off cats will decrease your power. If no cats caused a decrease in power then dragsters and stock cars would be bolting on cats for HP gains but you don't see that.

In my opinion you will need to be really throwing a lot of HPs out before it would make a negligible difference. If you had 500+ horses then I'd say it may make a difference. Our cats are pretty high flow from what I've heard and I don't cutting them off is worth the smell for lets just say maybe 3hp.

You will defiantly notice the odor, and so will any chicks you take for a ride. They will however just think something is wrong with your car. My fiancee made a complaint about the smell of a truck we were behind (no cats). To me its not worth it for a street car, especially an SUV, but i've got straight pipes on the motorcycle and will on the gasser i'm building.

I figured it only mattered in high horse power applications. I wont just go and gut my cats that's asking for trouble. Any real gains in my application would be marginal at best

 

[01ssreda4]

I recently did long tubes and a custom y pipe with no cats. Picked up a ton of midrange and top end power. These manifolds and cats really choke these engines back.

 

[gunslinger]

I recently did long tubes and a custom y pipe with no cats. Picked up a ton of midrange and top end power. These manifolds and cats really choke these engines back.

When you say a ton of power, can you quantify in hp? I'm interested in people putting these on a Dino before and after. I'd suspect a lot of the gains you feel are also attributable to the tune I'm sure you did afterwards. In other words apples to apples would be comparing your long tubes, y pipe no cats, and tune to a guy that did long tubes, y with cats, and tune... Not to a stock system.

 

[sumo]

I did 1 7/8 long tubes and had it dynoed. I made 50hp more than a truck that was similarly modified like mine

 

[gunslinger]

So you are saying having no cats increased another 50 hp over the same system with cats? That's more than I would have guessed. 50 hp would be worth the smell.