ripgtp97

iTrader: (2)

so i've got a 2000 t/a A4 with about 100k on it and I had it dyno'd for some before and after (still don't have any after numbers yet) but on to the story. When i bought the car the check engine light was on for the cats i was told. I had all ir provisions tuned out as well s o2 sensors and the cats, light went away. Whenever I accelerate real hard, a lot of the time the car will stall out. I cleaned the maf and everything i could think of, and figured I had some really bad clogged cats. I had it dyno's, about 5 pulls.. 2 of the pulls the car stalled out.. the other 3 the max HP i got was about 280.. and each time the gas was left off, quite a bit of black came out the back.. So what i'm wondering is, if these clogged cats could be the reason im losing about 20WHP??

**car was dyno'd with stock air filter and a borla non-adjustable catback
I also seafoamed the car about a month before this

71novaguy

iTrader: (2)

is filling your exhaust pipes full of cement an efficient way to increase exhaust flow?

ripgtp97

iTrader: (2)

noo.. but im wondering if just clogged cats would equal a loss of 20 horses!

Camaro_94

iTrader: (5)

LMAO!

Is the check engine light still on?

ripgtp97

iTrader: (2)

nope, check engine light is off.. and as i mentioned, rear o2's, cats and egr is all tuned out

71novaguy

iTrader: (2)

it can equal more. clogged cats do not equal 20 hp loss. it can. it can be more, it can be less. also look for a loss of rpm, when they really get clogged, you wont be able to rev as high

Camaro_94

iTrader: (5)

It could..... If its bad enough. It would be restricting the air flow.

ripgtp97

iTrader: (2)

that makes sense then, cause it was reaching max power at around 5500 rpm.. and i know it can get more than that

gta3uzi

You might be able to take your cats off and sell them. You could just have a shop weld in straight pipe in their places. If you don't care, read below.

If you have a 2000 you can take your cats off. I have a 2k Z28. The cats are bolted to your manifolds with triangle flanges and 3 nuts. SOAK THESE NUTS IN KROIL / LIQUID WRENCH FIRST. Even with this I wound up breaking a stud off of each of the manifolds. You will also need to undo the clamps that hold the cats to the Y-pipe. Soak these nuts as well.

Now that you have the cats out, which should have been pretty painful, you need to take a 2-3 foot long steel poking tool and a big hammer and pound the cat material out of them. Wear a mask or at least wrap a T-shirt around your face if you can't be bothered. The material the cats are made out of is nasty, nasty, nasty stuff and the crap your motor has been filling them with is just as bad. YOU DO NOT WANT TO BREATHE THIS STUFF AND IT HANGS IN THE AIR LIKE FOG.

After you've hollowed your cats out bolt those bad boys back on and enjoy your slightly louder / raspier exhaust note and your "free" performance mod.

ripgtp97

iTrader: (2)

thanks for the input and i would be doing that except I have my headers, and I'm just waiting for an off road Y pipe, for now the car is off the road for the winter and everything should be fixed in the spring, just wanted to make sure there weren't any other possible causes

JohnFrazee02SS

iTrader: (23)

Gears will make it dyno less too.

JM0523

CATS FTL
Mine are stinking so if i can find a shop cool enough to bag them im going to get them removed, every shop around here are ****** about cuttin them off.

71novaguy

iTrader: (2)

Oh yes. Pussies. They could only be fined tons of money for each cat they cut off, but yes, they are the pussies. Or, you could man up and cut them off yourself, then take it in and have them weld in pipe or whatever it is you are wanting to do with it.

blk/slvr02ss

iTrader: (21)

I think the Cats could rob 20 hp.I put just a Mac Off Road Y-Pipe on a 98 Z-28 i had and it went 3 tenths faster in the 1/4 so i would say it could but u will know when u dyno the car after there off !!!!!!!!!

JM0523

Already tried it, they wont touch it if it doesnt have cats.
The only way they can do it is if the vehicle is old and didnt come with them.

Finkledbody

Hollowing out a cat is a no no. Not only are they worth $100+ a piece because of the metals contained within. But also when you do hollow the cat, it creates turbulance within the gutted cats effectively slowing the the flow of gases through the exhaust system; reducing horsepower and mpgs. (If mpgs matter at all to the owner)

zracer323

iTrader: (12)

Why did you tune out the cats? A check engine light could answer your question for you. If it is throwing a code for your cats then your cats are probably bad!

StormesRacing001

iTrader: (5)

ripgtp97

iTrader: (2)

well i put in a scanner before i had it tuned out and it was saying the code for either rear o2 or the cats, so im pretty sure it is the cats, i was just surprised backed up cats would cause the car to stall under heavy loading and rob that much HP!!

itsslow98

iTrader: (18)

long tubes will change the location and readings of the rear 02 sensors which is why most people take the rear 02s out to begin with after they install long tubes. thats probably the code but your car shouldnt stall without them.