I have a stock 2.8 engine in a 87 GT. I was about to remove the catalic converter and replace it with a peice of exhaust pipe because it is about shot and leaking. The car is registered and used where there is no pollution testing. A friend said if I bypass the Cat. it will screw up the tune of the engine. Need your feedback please. Thanks in advance.

If I remember correctly I had a little bit of a idle issue, it would go up and down a little. The car itself was louder on start up but was able to quiet down after it warmed up. Other than that I never noticed a performance increase.

I don't think you will get a performance increase. The 4 and 6 cylinder motors in these cars are pretty much maxed out for horsepower without adding major components (turbo, nitrous). As far as any issues, I wouldn't see any. The car will just be a little louder. If I had the option here in California, I would remove it.

A friend of mine here has an '88 GT that he's been running for years without the cat. It didn't hurt the state of tune at all. Like others have said, it's a tiny bit louder. If you're not convinced, then you can buy a universal two way cat for under $100... which after all is said and done, isn't very expensive to help pollute less.

i have a piece of straight pipe in place of my cat and i have some idle issues

I can't see how anyone has issues with engine performance after removing the cat being that there are no sensors attached.

I have a "off-road cat delete" on my Fiero (its a bolt on from the fierostore, $30?). It runs fine. Only problem i have is it likes to fall out... If you have a welder its all good man. And i say do it, it makes it sound better lol Way better than a leak too.

Thats crazy that people say they had idle issues. When mine was removed I thought my car seemed to idle a little bit rough before it warmed up but i figured it was just in my head. Any way I agree with the it shouldn't cause any issues because there's is no post cat sensors.

[This message has been edited by Blue87Fiero (edited 07-07-2010).]

I removed my cat and put in a straight pipe like 10 years ago.. Never had any problems at all.. People who say they have idle issues, more than likely have a idle issue for some other reason.. It will be a little louder.. And your exhaust might be a bit more "stinky" than with a cat.. Performance increase? not really.. It will breath a little better since theres no cat, but unless you put a free flow exhaust and headers on to take advantage of it, it wont do much, if anything to increase performance.

But it does sound a little more beefy.. Of course i put performance exhaust on the same time i took the cat out, so i dunno how the stock exhaust sounds without a cat..

But no, putting in a straight pipe should'nt mess up your tuning.

[This message has been edited by Jonesy (edited 07-07-2010).]

My 85 GT I had a few years ago the cat got plugged up for some reason, I hollowed it out put it back in and still passed emissions (and that was when then tested exhaust emissions not just obd2 monitors) it is a clean running engine. Like others have said, was a little throutier sound but not obnoxious, sounded great to me, no adverse tuning issues noted.

------------------
If I only had ONE more part it will be finished...... famous last words.....

Your friend is probably thinking of OBD2 cars that have an o2 sensor after the cat to check that the cat is working. Remove the cat on those cars and the computer will cut back your power.

You should experience no change ,,the cat was probably used up years ago..so no harm in removal,,a new perfromance cat good for the air we breath
the ECM is used to the cat in the system,so a very minor change may be felt
Im running a dynomax turbo in place of the cat,,this has helped performance,,of course the muffler should be run in the stock position for best performance

The crossover pipe and catalytic converter are the two most restrictive parts of the exhaust system. A CAT is also a fire hazard as any oil leak can easily ignite and cause a fire on the superheated surface.
Those things were mandated by corrupt government bureaucrats who know nothing about automobiles. When was the last time that you saw a politican working on a car? They know absolutely nothing about them. All they are interested in, is stuffing their pockets with money at our expense. If CATS were so beneficila how come I know many people going through (and passing) state emissons inspections without them. Its all a ruse just to squeeze more money out of the taxpayer.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by Dennis LaGrua: The crossover pipe and catalytic converter are the two most restrictive parts of the exhaust system. A CAT is also a fire hazard as any oil leak can easily ignite and cause a fire on the superheated surface. Those things were mandated by corrupt government bureaucrats who know nothing about automobiles. When was the last time that you saw a politican working on a car? They know absolutely nothing about them. All they are interested in, is stuffing their pockets with money at our expense. If CATS were so beneficila how come I know many people going through (and passing) state emissons inspections without them. Its all a ruse just to squeeze more money out of the taxpayer.

Political rants go in Off Topic please.
Because the emissions on cars from the 80s suck with or without a cat, is not definitive evidence that cats are a bad idea. It is merely evidence that you don't know enough about the technology, and you are searching for something to complain about. The elements in some of the more modern cats reduce the evaporative emissions from the engine to almost entirely only oxygen and water vapor. The cat is a large part of why the series 3 3800 was the first internal combustion drivetrain to be certified as SULEV.

Removing the cat isn't going to give you an real performance increase, or cause any real tuning issues on the stock 2.8 (there are no sensors in the exhaust after the cat on the Fiero). Newer cars that have post-cat sensors might see some differences, and are more likely to see a huge difference in emissions.

if it's "shot" & leaking, cut it out. replace with a thrush "bullet " Glasspack 2" in, 2" out, 25 inches long, from Advance auto parts $18. You will Have to weld it on. just a pipe will be alot noisier

quote Originally posted by dobey: almost entirely only oxygen and water vapor. .

Lets not forget the main constituent (apart from nitrogen) - Carbon Dioxide - can't do a lot about that!

You can bypass the cat but any hp gain will be minimal or none at all. Your exhaust will also become much more deadly and polluting. One of the things a cat does is convert CO (carbon monoxide) into CO2 (carbon dioxide). CO will kill you quickly because it binds with your hemoglobin and won't let go easily. CO2 can only kill you by displacing oxygen. That does not even take into account the other dangerous fumes emitted by the engine that can cause lung damage.

I would be very careful working on the car with the engine running, even in open space. People die every year hanging on to the back of a boat because it only take a couple seconds of breathing a boat's exhaust before you fall unconscious. The main difference between a boat engine and a car engine is that boat engines don't have emission controls on them. So guess what happens when you take those emission controls off of your car engine?

[This message has been edited by Doug85GT (edited 07-08-2010).]

quote Originally posted by Gandalf: Lets not forget the main constituent (apart from nitrogen) - Carbon Dioxide - can't do a lot about that!

Carbon Dioxide isn't the big problem. Carbon Monoxide is. But if you want to lower CO2 emissions, the best solution is to stop breathing.