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post #1 of (permalink) Old 02-18-2004, 10:11 PM
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Cat Question

I buddy of mine has a 93 Chevy truck 5.7 tbi with a flowmaster cat-back system on it.

He wants to remove his cat but he wants to know if this will cause any adverse effects.

He wants to make sure the computer wont get pissed off [img]images/graemlins/smile.gif[/img]

Also will it make the truck any louder???
Help or hurt milage???

Sorry for all the questions
I told him I would ask, so I did.

Thanks [img]images/graemlins/grin.gif[/img]
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post #2 of (permalink) Old 02-18-2004, 10:52 PM
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Re: Cat Question

Check for o2 sensors. If there are ones after teh cat, then removing them is going to bring up a trouble code. It IS illegal to remove a cat from any truck that came with one from the factory, so if it was my truck and i wanted to get rid of it, i'd do one of two things.
1. Remove cat, and punch out all the honeycomb stuff wiht a BF screwdriver. Break it up and shake it out. Then reinstall
or 2. Break up insides of cat, and push exhaust tubing through it, and reinstall.

These ways, it will be a lot less obvious to cops/inspectors that you have dissabled your cat.

But remember, you won't pass smog without a cat, so if you remove it completely, be prepared to reinstall one/purchase a new one when smog check time rolls around!
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post #3 of (permalink) Old 02-18-2004, 11:23 PM
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Re: Cat Question

Will be much louder.
Won't piss off computer (O2 sensor is before cat).
Gas mileage stays about the same.
Disadvantage: fine/cost of new converter
Advantage: free flowing exhaust = happy engine [img]images/graemlins/smile.gif[/img]
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post #4 of (permalink) Old 02-19-2004, 07:41 AM
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Re: Cat Question

Those of us who breathe would appreciate it if you kept a functional cat on your vehicle...
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post #5 of (permalink) Old 02-19-2004, 08:19 AM
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Re: Cat Question

If he wants to free up the flow why not just get a new one?

I bought 2 magnaflow cats for my 98 and they are great. I have 2 o2 sensors before the cats and 2 after. The engine light hasn't been on due to problems from these cats.

On e-bay look up performance pedler. He's got a e-bay store and has real GREAT deals. Be alot better than a fine.
post #6 of (permalink) Old 02-19-2004, 10:27 AM
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Re: Cat Question

up until 95 you can remove with no problems to the engine. yes louder. marginal gains elsewhere. you can unbolt the exhaust at the headpipe/tailpipe flange and use a crowbar oir BFS to break it up and then start the engine and rev it up. it will blow out the pieces. bolt the system backtogether and yu're good to go.
yes it is illegal, and if you have smog tests then its not a good idea. whewre I"m at we dont have inspections so it isnt much of a concern.
and to the newbie who acts like he knows it all, any basic chem class will teach youthat the proces that the catalyitic converter starts happen naturally. granted it takes about 45min-an hour for the exhaust gases to make it to the same chemical composition, but it happens naturally. the platinum in the cat just starts and speeds up this we can all still breathe just fine without them. this naturakl breakdown does not occur fast enough in metropolitan areas to keep up with exhaust production though, so in bigger vities its best to have the cats. in the middle of nowhere who cares
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post #7 of (permalink) Old 02-19-2004, 10:29 AM
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Re: Cat Question

I'm pretty sure it's legal for end-users to eliminate the catalytic converters but I know it's a $2,500 fine for a business to do it. We haven't had any emissions testing in Michigan for like 15 years now. I think it was only Macomb, Wayne, and Oakland counties that ever did it.

Anyway, just put a piece of pipe in place of the converter.

However, Flowmaster is gay. They aren't the masters of flow (in fact, they flow pretty bad). I'd remove the Slushmaster and run just the catalytic converter. It sounds better than the dime-a-dozen everyone-including-your-grandpa-has-one Flowmaster sound.

Whenever you get rid of backpressure you'll gain power. It'll be a little louder.
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post #8 of (permalink) Old 02-19-2004, 01:14 PM
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Re: Cat Question

Removing the cat is illegal, regardless of who does it.
I just got 2 new ones installed, and on the certification form I had to sign, it states the penalties for removing them.
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post #9 of (permalink) Old 02-19-2004, 06:54 PM
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Re: Cat Question

WHat was the fine that it stated? I'm just curious.

Oh, and yes, you will gain hp with decreassed backpressure, but you want some backpressure or you will loose all your torque. And torque is definitely the most crutial on these trucks, where it takes a lot to get them moving and up and over obstacles, etc.
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post #10 of (permalink) Old 02-19-2004, 08:15 PM
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Re: Cat Question

Thanks for all of the replys guys

We dont have smog tests around here so it is not a issue

He doesn't have sensors after the cat.

Once again thanks for all the replys [img]images/graemlins/cool.gif[/img]

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