Hey all,

This may be a newb question but I've read and couldn't really get a straight answer..

My car pollutes and smells like a **** and is a bit too loud especially for the neighbors. I'll be moving into a new house soon and I am hoping having a new cat will quiet it down some.

Right now I have the stock cat, all rusted, AIR tube blocked off, and completely gutted inside.

Here is the one I'm looking into buying:
http://macperformance.com/store/prod...Product_ID=453

Here is the description (for some reason it doesn't show up on the page of the product):

"Part Number: 48792
Price: 74.50

Description: 5.4 Rear Wheel Horsepower gain! Fits MAC Header system or replacement Y-pipe.
Made from aluminized steel, no coating."

I have Edelbrock headers and their y-pipe, but I think the y-pipe is 2.5" tubing, would it fit directly with this cat since it's a 3" cat?

Also, since I don't have the AIR system installed, would this cat work properly without the AIR system in place? Or am I buying this for nothing and it will fail in a year? Also, will the cat make that much of a difference? I imagine it must otherwise modern cars would not have 2 or even 4 of them.

Thanks! Just trying to pollute less and not **** off people anymore.

 

Hate to bring this up again.. But will a 3" cat fit with a 2.5" y-pipe?

And will the cat function properly without AIR?

Thanks!

 

They sell reducers that you can install to step the 2.5" y-pipe up to 3" to meet the cat.

Will it work without air? Sure, but probably not as fast or as well as intended. Introducing air into the converter helps to increase the temperature more rapidly, and decreases the time it take for the cat to start functioning when it is cold. It will light off eventually, just take a bit longer.

 

Perfect that is the answer I needed. Thank you very much!

 

I found two on Summit that don't have the AIR provision, the only different between the two is that one is "stock flange" and the other, more expensive one is "slip fit". What is the difference between the two?

 

Not exactly. The diverter valve puts the A.I.R. flow to the manifolds when the engine is cold, and to the cat when the engine is warmed up. It would be the opposite if what you're saying is true.

 

It puts AIR into the manifolds to warm up the O2 sensor faster, right? If that's the case then it is not an issue in my case because I have a heated O2 sensor. What still remains an issue is the functionality of the cat without the AIR when the engine is warmed up (i will get a NON-AIR high flow cat ofcourse).

If my PROM is tuned and not running rich or lean (BLMs are 128 spot on plus/minus 2 points) then the cat shouldn't fail prematurely, right? I always thought it was because the car is running rich that the cat fails prematurely.

 

If your car pollutes and smells, chances are it is running rich. Cats don't like a rich mixture and you will clog it up very quickly. Make sure you resolve your other issues before putting an expensive cat on a car that is not running right.

 

No, it routes the A.I.R. flow to the manifolds in order to react air (extra oxygen) with unburnt hydrocarbons at the point where the exhaust is at its highest temperature. As the engine continues to run and the catalytic converter warms up, the extra oxygen becomes more effective within the cat, so the flow is then routed there.

A.I.R. predated O2 sensors and catalytic converters in the evolution of emissions controls.

 

So, I think it's safe to say that if I buy a NON-AIR cat and tune the car more to make sure it's running perfectly (not rich or lean) then the cat will function as it's intended? I am assuming that a cat with functioning AIR made to accept the AIR injection will be more efficient than a non-AIR cat.

 

Oookay.. Just intalled the Walker 3" cat from SUmmit.. It's a non-AIR cat meaning that the AIR provision is blocked off.

The car is noticeably quieter and the sound is thinner. It's fine for me as it was extremely loud before.

The crap smell is alot better than before as well. It's bearable now.

My only concern is that the car overheats now. It's strange really. I pulled out of the garage and within 2-3 minutes of idling to warm up the car, check engine light comes on.. I make nothing of it but the fact that engine sounded like it just de-tuned itself.. Odd.. So I start driving and the light goes away. The car feels a bit slower than when I had a gutted cat. The car was fine until I pull into the parking lot at my work and I let the car idle. It idled ALL the way up to 230 and fans kicked on. I was about to turn it off because I was nervous.. The fans turned on and it was okay but the heat climbed very quickly. This is a brand new cat! Would this make the car overheat more than usual??

Another thing to mention is that my fans weren't working before this. I just installed a new relay and pigtail and now they work, but they turn on at 230! They are supposed to turn on at 180 (180* thermostat as well as a PROM tuned for them to turn on at 180 and off at 160).

Any ideas? This may not be related to the cat at all but I just wanted some opinion on this.. I will pull out the tuning stuff tonight to see what's going on and what code the engine threw for that very brief minute.

 

Wasn't related to Cat at all.. The temp sensor in the block was busted thus making the fans not turn on at the right temp.. DOH!!