Facts and Opinions about Catalytic Converters. (Page 1/2)
Pontiac Fan 89 DEC 17, 01:46 PM
Hi everyone. Purchasing my first Fiero soon, really excited. Put down a deposit with the owner and picking it up when the title comes in.

I have read a few of the ancient posts about catalytic converter removal/replacement, and would love your guys input on the topic. I'd like to lay out all of the previously mentioned issues and questions regarding catalytic converters in one post for future reference. The reason I'm asking is because I will likely need to go through the entire exhaust on my 86 SE, from the headers down. At best, a few inserts of new piping and at worst, an entire new system is necessary.

So, my main question is, should I do one of three things:
-Cut out the cat when patching/replacing exhaust
-Keep the cat if its not clogged when patching/replacing exhaust
-Install an aftermarket high flow or oem new cat

Question 1: Obviously cutting out the cat will negatively impact the cars emissions. I've heard that cutting out the cat can actually slightly reduce engine power. Is this true? On older smog era cars I know for sure that cats play a role in reducing flow. Does the Fiero suffer from this as well?
Question 2: If the cat is shot, is it worth buying a high flow, staying oem, or removing it?
Question 3: Should I even attempt to repair an exhaust that is disconnected from headers down or should I look for an entirely new system?

I'm really excited to start working on and driving my Fiero! It's one of my favorite parts of automotive history and has been one of my dream cars for a while.

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1980 Honda XR80
1975 Oldsmobile Delta 88
1986 Pontiac Fiero SE

Patrick DEC 17, 02:04 PM

quote
Originally posted by Pontiac Fan 89:

I have read a few of the ancient posts about catalytic converter removal/replacement, and would love your guys input on the topic.



Lots of current threads. Here's one from two weeks ago - Catalytic converter delete

My opinion... install a new cat. Inexpensive, and non-restrictive.
Pontiac Fan 89 DEC 17, 02:32 PM
Thanks Patrick!
cvxjet DEC 17, 04:25 PM
The Fiero V6 cats are a honeycomb matrix- non-restrictive....I doubt if you would notice any difference either way by removing it...just stinkyer exhaust. I have an F-body 3.4 long block under the original '85 induction system. I lost the cat back a few years ago....Bought a new one and drove to Hayward to have it installed....after, I could not feel any difference- But I did not try to quantify the situation......

[This message has been edited by cvxjet (edited 12-17-2019).]

Pontiac Fan 89 DEC 18, 01:00 PM
Awesome, thanks for the info! New cat it is.
jessesmith121 DEC 18, 01:12 PM
Being in a Free State (no emissions or safety inspections) like Iowa I have deleted and straight piped the cat in every fiero I have owned. If I lived in an emission state I would have the high flow replacement cat installed. Not sure on the performance difference as the car really isnt a race car anyways (we are talking 140hp on an antique), but it sure does sound much better. I have never thrown any trouble codes related to them. So for me, no issues, better sound, more room when working on things... no downside for me.

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86 Fiero SE 5 Speed - Junkyard
84 Fiero SE 4 Speed- Sold
86 Fiero SE 6cyl 4 speed M19 - Sold
86 Fiero SE 6cyl 4 speed (25,000 miles) - Sold
87 Fiero SE 4cyl 5 Speed - Sold
86 Fiero GT 4 Speed- Sold
88 Formula 5 Speed T-top - Sold
87 Fiero SE 6cyl $ speed swapped - Sold
88 Fiero Formula 5-Speed - Sold
86 Fiero GT 4-speed - Sold
87 Fiero GT 5-Speed - Sold
Countless parts cars

Falstaff DEC 19, 11:12 AM
I cut the cat off my '86. It runs just fine without it. In Michigan they don't test for emissions so it doesn't really matter. Since the converter is basically under the engine it does run the risk of starting a fire if oil leaks on it.
Gall757 DEC 19, 05:36 PM

quote
Originally posted by Falstaff:

I cut the cat off my '86. It runs just fine without it. In Michigan they don't test for emissions so it doesn't really matter. Since the converter is basically under the engine it does run the risk of starting a fire if oil leaks on it.



It's true, in downriver Detroit, one more polluting car will not be noticed.
ChuckR DEC 20, 07:16 PM
I agree that removing the old and installing a new is best practice. I know most don't care of environmental impacts but it is a low cost fix for that and the stink of not having one. Being a small car, that stink will work its way into the cabin. The new cat will not harm performance and will make driving the car more enjoyable on ALL the senses. And as a bonus you don't harm the environment around you as much as if you took it off and left it off.
Patrick DEC 20, 07:37 PM

quote
Originally posted by ChuckR:

I know most don't care of environmental impacts...



Most what? People who don't breathe? Do these same people defecate in their drinking water?

It's not like the benefits of a catalytic converter can't be measured. There is nothing to debate. Catalytic converters do indeed reduce toxic gases and pollutants from the exhaust of internal combustion engines.