Questions on Removel of CAT converter - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 10-12-2003, 11:32 PM   #1
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Default Questions on Removel of CAT converter

I pretty sure my catalytic converter is bad. What i was wondering was that if i remove it and replace it with a straight pipe would that allow of better gas mileage because im broke college student, and i need alot better gas mileage and my car is not even getting 20 mpg out of town sometimes even 10 by the way my bonneville is a 92 se not much but its got some get up and go well usually but lately it just been acting like oxygen sensor is bad but i just replaced that. between 45 and 55 it just is dragging out like its not getting the fuel air ratio. How easy is it to replace like meaning do i have to remove the whole exhuast or can i just slide it out easy i mean if its weld i can deal with but i dont trust myself with removeing the exhaust. Mainly i am jsut worried that i wont get good gas mileage? if anybody can help me with it i would appreciate a lot
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Old 10-13-2003, 12:23 AM   #2
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One thing I can tell you, is you would fail emisions with out a cat. I'm a new owner of this car and I won't pretend to be an expert but I know back pressure is an issue that you will have to deal with especially on a na motor. From what I've seen a high flow cat may be a good idea but from what I've been told you don't want to open up the exhaust to much.
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Old 10-13-2003, 01:09 AM   #3
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This link says you can check it with a vacuum gauge. I would take it to a mufler shop and have it tested.

http://www.batauto.com/articles/vacuum.shtml
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Old 10-13-2003, 11:37 AM   #4
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Default Re: Questions on Removel of CAT converter

Quote:
Originally Posted by morsmortis
I pretty sure my catalytic converter is bad. What i was wondering was that if i remove it and replace it with a straight pipe would that allow of better gas mileage because im broke college student, and i need alot better gas mileage and my car is not even getting 20 mpg out of town sometimes even 10 by the way my bonneville is a 92 se not much but its got some get up and go well usually but lately it just been acting like oxygen sensor is bad but i just replaced that.
If the convertor is clogged, replacing it will get your gas mileage back since your engine can breathe again, and you won't have to keep punching the gas pedal just to keep going. Don't bother with a straight pipe; the hassle of putting that in by yourself isn't worth it, no legitimate exhaust place is going to do that for you, the car will smell like a cheap lawnmower afterwards from all the hydrocarbons in the exhaust that aren't getting converted, and you'll flunk emissions testing anyway, if you have any in your area.
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Old 10-13-2003, 08:11 PM   #5
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also u will get alot of backfireing so i reality it will sound like a jolppy
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Old 10-14-2003, 09:53 AM   #6
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Quote:
Originally Posted by joe
also u will get alot of backfiring so in reality it will sound like a jalopy
Good point. With a straight pipe instead of a convertor, you will be reducing the system backpressure _below_ what the car was designed for, possibly leading to some slightly weird results. The convertor does not actually create a _lot_ of backpressure, but the car is designed for all its components to actually be there, and you don't buy yourself anything by leaving off the convertor.
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Old 10-15-2003, 10:29 PM   #7
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Yeah but all the exhuast places in my area charge high price its like 190 for replacement and that dont do a very good job, ive worked for gm/walker mufflers and ive seen how much better the can be so when i look at what they do i look away in disgust. I just dont have all the tools to replace the converter not to mention the money. though it only cost 89 for one at autozone. what emission tests? you have to pass emissions tests.thanks for the advice though i do plan to replace someday
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Old 10-16-2003, 12:08 AM   #8
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Running a straight pipe will do more worse results than good ones.....
A better choice is to install either a new CAT, a resonator instead of a CAT, or hollow out the old one & re-install it again.
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Old 10-16-2003, 11:34 AM   #9
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(Please don't be offended by what I wrote below...)

Quote:
Originally Posted by morsmortis
Yeah but all the exhuast places in my area charge high price its like 190 for replacement and that dont do a very good job
Agreed; what you're mainly paying for is convenience, and then you hope to Gawd that they do the job right as well, not just quickly.

Quote:
I just dont have all the tools to replace the converter not to mention the money. though it only cost 89 for one at autozone.
Well, ya know, sometimes things just cost money. You're driving a flagship car, not a two-bit ricer, and sometimes that difference can bite you (although realistically, I don't think the price of a replacement convertor would be all that different across different models, especially for aftermarket convertors). Be grateful it'* not, say, a broken transmission.

The main thing is to buy the part. At that point you can do all the rest of it yourself, if you don't mind dealing with some rusty pipes, getting under the car, etc. That'* part of owning a car, and it'* the part you get to avoid when you have more money: you can pay somebody else to do the yucky stuff if you don't know how, or if it'* too complicated, or if you're too busy.

For example, I've got another car in my garage with a broken MacPherson strut that I could have back on the road tomorrow if I wanted to pay somebody else several hundred bucks. Instead I'm eating the cost of the replacement struts myself -- no way around that, of course -- but doing the labor all myself, whenever I have the time to work on it.

Note that Auto Zone also offers free tool rental on hard-to-find stuff: you put down a deposit (typically the purchase price of the tool), and when you're done with it you bring it back for a full credit. Ask them about that. I'm probably going to get my MacPherson strut spring compressor from there for a $35 deposit, and return it when I'm done.

Quote:
what emission tests? you have to pass emissions tests.
Ayup, here in the Chicago area I have to put the Bonneville through a treadmill test every two years. No problems so far, fortunately.

Repeatedly failing (or ignoring) the tests can get your license plates suspended.

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thanks for the advice though i do plan to replace someday
Good luck; we'll offer whatever help we can.
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