I know i know, I fyou take off your cat emmisions test will kill you....but i live in good ole ALABAMA(LOL) where the cop cars are prob straight headers!...in other words i wont get caught...If I take it off what all will it affect and how much HP should I gain?


Optima deep cycle battery
NGKs
Bosch wires -:x
painted calipers
GReddy headers-custom flanges
Monza pipe_Arospeed Bomb muffler
sidemarkers-blue
2 impp 12's
BOLT 300 watt amp-DONT ASK<DONT TELL
MA AUDIO Digital 1 farad CAP
Bandpass box
2002 model Sony Xplod CD player--All props on audio to-E-Rock.

Will i get a CEL if i just test pipe mine??????
How much can i do it for? What will my gains be in HP and torque
TIA

taking off your cat, will give you some hp, but probably not enough to feel, you will lose needed low end torque that will hurt you greatly due to the loss in backpressure created by not having a cat.

by taking the cat out, I would think that you would get a cel due to the fact that their is an o2 sensor after the cat. and if doesnt sense enough o2 in the exhaust flow, it will either trigger a cat efficiency failure code (72) or an o2 sensor code (21)

someone please correct me if im wrong on both of these issues

thanks

matt

I have heard of people just cutting out another bung and relocating the sensor in the test pipe. Others say do the same but wrap the sensor in aluminum. Anyone with no cat , have you had any probs?

there are quite a few people on the board who have either gutted their cat or use a test pipe with no adverse effects. Dave didnt even get a CEL when he installed his test pipe and he is turbo. As far as not giving enough backpressure, backpressure is ALWAYS bad. What you want is maximum exhaust gas velocity. If your car isnt producing enough gas for a certain size pipe you will lose that velocity thus losing power. I dont think removing the cat can be detrimental to performance. If you dont have emmisions testing go for it

So should I get my cat out then? I'm running an Auto with stock size piping but a Magnaflow muffler. Will I lose alot of low end to notice and will I gain anything? Or is it better to keep my $30 bucks and leave it on?

Thanks.

OK.... Please help me give the final word on Test Pipes. Then move this thread to the 'things we've seen before' conference.

If you remove your catalytic converter, you will get a little performance boost. You will get even more of a performance boost if you have other modifications that allow your car to breath easier.
ie. Intake, Exhaust, Throttle Body, and yes Turbo.

Now you may notice a little low end torque loss, but probably not much. You will like what you hear and feel on the top end, however there are consequences to removing your catalytic converter.

1. It is illegal. Even in states that to not have emmision laws, it is still illegal due the fact that tampering rules with emmision devices on your car are controlled by Federal laws.

2. You will most likely get a Check Engine Light for having an inefficient catalytic converter (because its not there). This usually results in a CEL or MIL code 72. Even though our tech manuals say that the catalytic converter inefficient code is 64, you will get code 72. This is probably due to a misprint in the manual. The Dodge Neon tech manual that I have seen show this as code 72 and they are our closest engine relative. Some people do not get a CEL due to other modifications or a really clean engine, who knows?

3. Your downstream O2 sensor (after catalytic converter) will most likely not last as long as it should. It will be measuring the same amount of stuff in the exhaust as the front one. This does not really matter because you will probably replace both O2 sensors if one goes bad.

4. Your car will be much louder than before. Some people like the noise, some do not. The new sound out of your exhaust will probably be a little higher pitched due to more exhaust valvetrain noise not being absorbed by the catalytic converter. (how your car will sound can be completely debatable)

There are some other differences in the methods that people use to remove their catalytic converter.

1. Most people gut their catalytic converter. This involves removing the catalyst material inside the catalytic converter and then putting the empty shell back on your car. I do not recommend this and here is why.... I did this originally because my catalytic converter was clogged up. It was an easy fix, but afterwards my car's exhaust note was messed up. It sounded real bad and the empty gutted catalytic converter under my car acted like a resonator of some sort which made the inside of my car drone while on the highway. I did get CEL code 72 and also the code for the EVAP system.

2. The preferred way to remove the catalytic converter is to replace it with a Test Pipe. This will allow the flow of exhaust gas to smoothly exit your vehicle, but at the cost of a higher pitched and much louder exhaust note. The pitch volume of the exhaust will depend completely on the type of muffler you are using and if you are turbo'd or not turbo'd. I am using an off the shelf Ractive muffler, so I get a little buzzing sound above 5000 rpm's. (this will soon change, Thermal R&D here I come)

3. The most preferred way (my way) is to use a resonated Test Pipe. Basically it is an off the shelf resonator (or custom) put in place of the catalytic converter as a Test Pipe. This will eliminate a little of the noise (10%) and reduce the pitch of the exhaust note. I picked up a 16.25 inch long, 2.5 inch inner diameter resonated Test Pipe from www.testpipes.com for $50 shipped. The flanges were adjustable and it fit well and works well. Now when I go on the highway my car is not as droning as before and the car seems smoother to drive every day under normal conditions (this is determined by a seat of the pants testimonial).

I am currently working a way to modify the after catalytic converter O2 sensor to see less of what it is supposed to see in your exhuast. This should turn off that CEL light when code 72 is present. I will keep you up to date on that.

-Jared
96 GS
Melbourne, FL

I have ZERO CEL lights and I have had my straight pipe for a couple months.

Can someone give me some numbers? cause if it is only like 2-3 HP im not even gonna mess with it....


Optima deep cycle battery
NGKs
Bosch wires -:x
painted calipers
GReddy headers-custom flanges
Monza pipe_Arospeed Bomb muffler
sidemarkers-blue
2 impp 12's
BOLT 300 watt amp-DONT ASK<DONT TELL
MA AUDIO Digital 1 farad CAP
Bandpass box
2002 model Sony Xplod CD player--All props on audio to-E-Rock.