• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

CATALYTCIC CONVERTER QUESTION

F

fbuhler

SM 2003
Full Member
Joined
Feb 13, 2003
Messages
393
Location
HAMILTON, MT
logo.jpg
REPLACING HEADERS... CATS. ARE RIGHT ?THEIR.. hmmmm... ?WHAT WOULD HAPPEN IF I REMOVED THE CATALYTCIC CONVERTER? MORE HORSE POWER? BETTER OFF THE LINE? LOUDER?

WHAT DO YOU THINK?

LETS HEAR IT!

THANKS,
FBUHLER
 
louder for sure...and maybe more hp...but also illegal and more pollution will result...so you can cry about the heat in the summer or the lack of snow in the winter if you do this...

i couldn't help myself :cool:
 
You would have to deal with the oxygen sensors which there are one on each cat and they feed info to the computer.
 
If you punch out the catalyst and leave the housing you will have a place to keep the o2 sensors. You have to use the front sensors. They tell the computer whether you're running rich or lean.

Keep the rear installed as well. Eventually you get a trouble light but it will only tell you that the cats are not working properly. It won't change how the engine runs. It just notifies you that the emmission system isn't performing.

It will be a LOT louder! Way too loud for my liking. I ran it that way for a while when one of my cats melted down. The exhaust fumes will make your eyes water.

kw
 
You really wont gain anything as the stock Cats flow very well.., it will be a lot louder.., you could install rear O-2 sims in place of the rear O-2 sensors.., they will allow the computer to perform correctly without the Cats.., but it really not worth the trouble for no real gain....

Butch.
 
One problem you might have is the record of excess emmissions will be filed in the computer and can be read out by the dealer, on star, and the local EPA guys can also read it out thru the OBD ll, the fines are large if you are caught, and most importantly it won't make much difference in performance.

Bill
 
It will most likely be louder. It is deffinately illigal. In Illinois you can not pass emission tests without them. In my opinion (which may mean nothing) you won't get anout HP to bother with it. There are better (LEGAL) ways to get more HP than what your thinking.
 
You will have to watch it in Pa soon as the new inspestion laws start soon and will be taken from the computer instead of from the tail pipe some green people don't like this but can't do anything about , will be looking for any trouble codes from computer
:eek: :eek: :eek: :eek:
 
OK HERE IS THE DEAL. I was looking for louder and more power but thanks to your advice i decided to leave the cats. but i did cut off the exaust down the pipe a little bit right before my glasspackes. ;D BOOM just what i wanted a LOT louder. It now sounds big and mean.

now for some more questions:

1. Do most states require for a muffler?

2. Emmisions, does the muffler have any thing to do with that?

thanks,
Faver Buhler
 
Im afraid Im gonna be controversial here!

Anyone who says that cats don't lose HP is not being sensible. If that were true, every racer in the country would not rip them out, along with the mufflers, at the first opportunity!

I have first hand experience of the benefits and would expect about 10% extra HP (plus 1-2mpg) from dumping the cats. I did this on my Silverado 5.7 and picked up about 20RWHP.

My 2500 Av is about to lose its manifolds, cats and mufflers. In their place, a set of TOGS headers and 3" straight thru mufflers will go in with 3" pipes exiting in front of the near side rear wheel. If that lot doesn't produce an extra 50rwhp, I will eat the cats!

The cats do not flow well compared to a short length of 3" pipe any more than the muffler does. The standard exhaust system is absolutely horrid with a small (2.5")diameter outlet from the manifold and two steps in each pipe just after the manifold. The cats have an O2 sensor in front of each, which must be re-installed with the new headers. The two 3" exhaust tubes enter and leave the muffler separately but combine itno a single 3" tail pipe with a very sharp Y-piece straight after the muffler. Also, there is a flattening of one exhaust tube where it crosses a chassis cross member. . yuk!

My truck does not have O2 sensors after the cats, though there are blanked off plugs for them. I got my truck from Canada, so the US ones might have these sensors fitted. In any event, they only monitor the effectiveness of the cats and have no bearing on engine performance.

As to the whole emmissions question. . .you pays your money and takes your choice. . .
 
That is all well and good for where you live - unfortunately many of us live in areas where emission control is mandatory. :C:
 
We shall see if eating of cats is required :eek:

I have lots of readings from my Tazzo and will do a set of runs after exhausts are changed. Even if I'm wrong, I'll post the results for everyone to see. . .promise!

I have been racing cars for neary 20 years now with some success and there was a time in the late eighties and early nineties when european car manufacturers were fitting cats as stadard but they were not a legal requirement in UK. I have helped dispose of about a dozen cats (not the furry kind!) and a 10% increase is typical. I even recently helped fit a "racing" catalyst to a friends car and the difference was. . .zip. . nada. . just a bit more noise.

Think about this: de-screening a MAF is reckoned to gain a few hp. Think of a cat as a great thick MAF screen in your exhaust. :0:
 
A 10% increase is pretty good considering most OBD-II vehicles shoot zero pounds of backpressure when tested at the front of the converter, stock. Go figure..... ;D
 
Maybe some tabasco sauce would go better with cats.

No way, especialy running 3"ers

Where in Canada did you get your Avy.??? as we do have sencore up the wazu (not as bad as Cal.) but close.

But what do I know 2? worth.

G. :cool:
 
Bumping an old post up the line here. I am also in Canada and have no need for the cats and I have also noticed a benefit to removing the cats in my vehicles. They also stink when they arent working properly. I was looking at the sts turbo and I think it would work better in the location of the cats so this is why am bringing this up again. Is there anything you can do to not have the check engine light come on and possibly lose power/mileage due to the computer trying to fix the problem?
 
Let's get this thread going again!!! >:D  I am interested in a little more noise in the muffler as well.  I have a Corsa Sport system on my truck and although I love the sound it makes, I wish it was a little louder..Anyway of killing the sensor light from the "punched out" cat?  Any other ideas of adding a little more rumble??? ???
 
TRIPSZ71 said:
Let's get this thread going again!!! >:D I am interested in a little more noise in the muffler as well. I have a Corsa Sport system on my truck and although I love the sound it makes, I wish it was a little louder..Anyway of killing the sensor light from the "punched out" cat? Any other ideas of adding a little more rumble??? ???
Click to expand...

put a Flowmaster 40 on there in lieu of Corsa....hehehehehe
 
Gotta work with what I got...especially after the $700 bill.  I do like the way My Corsa sounds...just a little more volume >:D
 
My Cobra LOVED a off-road X-pipe with no cat's ;D but that's a totally different beast.  Ask MurmanZ71 what it sounds like >:D. 
 
Ok guys, this is a very easy fix. The SES light will not come on after removing the cats if you install O2 simulators in the place of the rear O2 sensors. The front ones need to remain in the stock location but the rear ones need to be replaced.

When I had my LS1 Trans Am I removed the cats and the performance difference was very noticable. The car was a lot quicker and sounded extremely mean.

You can get a set of O2 sims from tbyrne, site sponsor. As a matter of fact thats where I bought the ones that where on my Trans Am.

Gerry
 
You must log in or register to reply here.
Back
Top