cats....or no cats?

jambird

Registered User
i'm sorry for asking this if it's an over asked question, but i'm gonna up grade my exhaust and i want to eliminate the cats. is this a good idea? what are some pros and cons of doing this? a person told me not to because of back pressure issues. what do i do about that third O2 sensor?

other thing i'm gonna do to it is get a hi-flow resonator maybe new piping and either flowmaster or borla mufflers.

any input on my question would be just awsome!

thanks, Jamie
 
jambird, I have a 90auto sc.Mine only has two o2 sensors.
So I am able to run with cats or with out cats.

Maybe if you list the year of what you have someone can
give you some better help.
List the year,stick shift or auto.

randy
 
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What are you trying to achieve?

Are you going to race around or daily driver. Do you have an EGR?
I have an 89 the side that has the EGR has the cats in it. I drive my car in the winter this helps it to warm up the motor.

The other side has been gutted. It has no EGR. It is open I have had no problems yet.

If you are going to drive daily. Use CATS. Use HI-FLOW cats these will help your engine last longer in cold climates.

If you are going racing Get rid of them and open the exhaust up.
 
I always suggest using cats. No sense poluting the environment for that tiny bit more HP. I'd stick with high flow cats.

What are you local laws in terms of pollution control on your vehicles?
 
Cats...

The Cats will also dampen some unusual resonances in the exhaust. So It can queit things down a bit when the cops come by.

Also you'll pass emissions. If you need to do this on a street drivine car the answer seems obvious.

Although I am unsure about the previous poster that mentioned that Cats will make a engine last longer in the cold climates. Catylitic converters haven't been used widespread on cars until 1976. So how long did cars last in the winter time before then?

And for the first few years that Cats were available, they caused all sorts of havoc on cars, especially clogging up in the winter time cause they were not placed closer to the engine where they would light off faster.
 
Well Deep 6

What is the EGR for? I have learned a little back pressure not alot is a good thing. The valve train seem to last longer. Well at least in my two cases.
 
E.G.R. - ehxaust gas recirculation - Un-needed cowcrap, unless you have emissions to worry about. EGR puts hot exhaust gasses back into the blower inlet before the blower, thus, reducing power and performance, however, this is a critical component in emmisions control. This EGR, helps in conjunction with the cats to give a clean burn, and keep our environment clean.

In an unrelated sc egr story, I capped the egr on my buddy's 97 neon. Now, the plastic intake manifold stays luke warm, instead of burning hot. Probably was good for about .2 seconds in our e.t.'s for 1/4th mile. Last run at the track, it ran a 15.8, and this was on a 85 degree day. Since, we capped egr, and pulled the cat, all in all, at our 1/4 knockoff track, we increased our mph by about 3mph. It was definately one of those improvements felt in the seat of your pants.
 
EGR is used to reduce the Oxygen content of the air charge, this in turn leads to a slower, cooler burning with lower nitrogen oxide emmisions and detonation reduction.

The problem is that most car companies are too cheap to put in a EGR cooler, so you also heat up your intake charge. The added heat completely removes the detonation reduction and actually makes detonation much more probable.

The EGR also adds in a lot of particulate matter into the intake because the bean counters don't allow for a filter either. So you get that nasty black crap all over the inside of your intake from the PCV oil mist and exhaust mixing.

Properly implimented EGR would not reduce power, but we all know how things are really done.

Aaron
 
Yes, the black carbon in the intake is pretty nasty. I took a towel and cleaned out that of the neon when i did my friends. The car blew a puff of dark smoke when It was fired up first. An egr filter is a good idea, you should suggest this to some car companies.
 
I would say that you should really make sure you don't need them in your state. Here in Maryland they sometimes check with a mirror to make sure they're on the car. If not, they may fail you. I'm going to be doing my exhaust soon, and was originally thinking about gutting my cats. This, however, will not reduce the 90 degree bend above the driver's side cat. I've decided to go with High-Flow cats. I say if you're going to do it, do it right the first time.

Matt
 
My 90 auto has no EGR.But I do have high flow cats.
I am going to take the cats off,when I switch headers.
Where I live, we have no smog checks.

randy
 
pastera.... excellent ....somebody that knows what the egr does ...

the egr valve tube runs into the exhaust manifold and not the cat..

right hand side has O2 sensor is in downtube just before the cat
....lefthand side has O2 sensor in exhaust manifold..

cats or not ..well for a country that dumps 200 million tons of pollutions into the atmosphere a year ..do you think you will matter ...your grand kids may need a third lung on the other hand ....dave
 
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Mine's like Randy's.

Some of the '90 AOD's didn't have EGR.

I've got shorty headers with O2 sensors in both and HighFlo CATs. As you can see from David's post, you can still make LOTS of power with CATs installed. ;)

Lee
 
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I think I see two 3 inch cat going in my car..yeahhhhhhh...yeahhhh...I would definately put them in if you can afford the extra 150-200 for the cats..You wont notice a power loss with them so long as your exhaust si free flowing, plus like others have said it will dampen some resonation
 
ON my turbo powered bird.All I run is one cat with 3inch pipe
and no muffler.And it is very quiet.

randy
 
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How do you, when adding the Flowmaster system with high flow cats deal with that 90 degree bend? Or in other words how does the system look (in words) starting at the manifolds?
Thank you,
Tom
 
cats or no cats

My car is a 1990 with a late model gas tank. I went with headers to high flow cats to real dual exhaust and dynomax mufflers in the stock position. From the back it looks stock has a quiet idle. I have to pass polution so it worked out reak nice for me.
 
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