Removing catalytic converter for more BADASS exhaust!


LOUD-ASS-SIERRA
01-13-2006, 05:02 PM
I have a 94' sierra ext. cab. It's got a 5.7 and 350 motor. Last summer i put some duals on it from the cat-back. Its got 2.5 in tubing from the cat and tops off with 3.5 in tips straight back.

This is VERY LOUD, yet a couple buddies of mine have there trucks even louder. I have thought of two different ways to make my truck louder.

1. Having a cat-back exhaust with 3" inch pipes and no tips or possible 3.5" in or 4" tips to finish it off. This would then need me getting a new high flow 3" inlet/outlet cat.

OR

2. Keeping my exhaust i have on now, and removing my catalytic converter. This is what I have been wanting to do.


I guess im wanting to know if one, has anyone done this to there trucks? I looked threw on this page and all i see is rice-boy honda civic forums about removing cat's for more horse. Well, i could care less about horsepower i would just really like it louder than it is already. It's a beautiful truck, and im trying to get a pic on on here yet i just registered today.

I know there are some legal issues and what not about the emissions and 02 sensors. Has anyone that's done this ran into some of these situations? I would like to take off my cat and not run into any malfunctions with the engine or reading it might affect.

Another thing, we all know this is highly illegal. Of anyone who has taken there cat off there trucks, how did you do it? Did a muffler shop do it? A friend?

Let me know what you guys think...

horse482
01-13-2006, 06:25 PM
On a '94 you don't need to worry about the O2 sensor there aren't any after the cat, unless it is from california. But it is against federal law to remove the cat. I know lots of people that have done it, most are running 3" with a strait through muffler (racemag), very loud.

heavyredchevy
01-13-2006, 08:34 PM
If you want your truck really loud, just get a cut out. It will save you a lot of trouble. Headers also have a bit to do with the sound, if you dont have any, get some. Theres nothing louder than a TRUE dual 3'' exhaust. Im not really sure why you would want to do this, it will kill your gas mileage, and no bottom end without backpressure.

LOUD-ASS-SIERRA
01-13-2006, 09:52 PM
Thanks for the help. I really don't mind i already get around 12-13 mpg as it is. And as for a cut out... You mean simply a piece of pipe to fill in for the cat missing? I've seen a few universal catpipe, test pipe, straight catpipe, what ever you wish to call it, on eBay. This might be the best way to go.

I've currently got 2.5" pipes to the 3.5" tips. You think to not worry about the O2 sensor and engine problems and legal issues with it , it would be best to just try to upgrade to 3" straight pipes ?

67malibu
01-13-2006, 09:54 PM
I used to run an '88 K1500 350 with just dual Flowmasters, full length headers, 2 1/4" true duals, crossover, etc. and it was loud (borderline obnoxious) and got 21 mpg on road trips. Then I moved and the truck had to pass emissions. With a pair of high performance cats the mileage dropped to 19 mpg and the then stock engine no longer chirped the tires from 1st to 2nd. The O2 sensor is in the driver's side header and the engine didn't act like it knew the cat was missing except for a noticeable increase in torque and mileage. There were no issues with backfires, etc but this is a TBI engine. I didn't want the $10,000 fine North Carolina imposes for removing the cats (even though I was in Georgia when I yanked the entire stock exhausts out) so back in they went.

cbongo247
01-13-2006, 10:25 PM
I have a 94 chevy w/a 350. i have had duals on it for about 4 years now and i have found that, the stock three inch with the converter, split off with a Y pipe into the dauls sounds the best. I took the converter off for a while, but i thought it sounded like shit. like a boat out of water. to loud and obnoxious! actually even noticed a decrease in power and torque, probly cause the sensor didnt get up to temp, therefor too much fuel. no check engin lights came on.
Again, with your 94 i would highly reccomend keeping your cat. then after the cat, split the 3" into 2 1/2" duals out the back. oh yeah a key part is having at least 3 1/2" tips! i have 4" by 24" on mine. find some similar and you will be happy! trust me! Its loud enough to make a big statment, at 60mph the radio can easily take care of the rumble on the long trips, also punching it at 60mph surly lets others know you are coming!

LOUD-ASS-SIERRA
01-13-2006, 11:19 PM
Well the thing is I have stock 2.5" pipe, topped off w/ 3.5" tips. With out taking the cat off what would you say i should do without getting a whole new exhaust package for my truck. The only thing i can think of now would be upgrade the tips. You think it would sound any better with 4" inch tips from the 2.5" pipes? I really think the best way to get it louder i guess with out taking the cat off would be upgrading to 3" inch pipes.

Check out this link and let me know what you think about putting one of these on to replace my cat...

http://cgi.ebay.com/ebaymotors/102mm-2-5-Universal-Catless-Pipe-Test-Pipe-Straight-Cat_W0QQcmdZViewItemQQcategoryZ33742QQitemZ8029000 239QQrdZ1QQsspagenameZWDVW

heavyredchevy
01-13-2006, 11:59 PM
Thanks for the help. I really don't mind i already get around 12-13 mpg as it is. And as for a cut out... You mean simply a piece of pipe to fill in for the cat missing? I've seen a few universal catpipe, test pipe, straight catpipe, what ever you wish to call it, on eBay. This might be the best way to go.

I've currently got 2.5" pipes to the 3.5" tips. You think to not worry about the O2 sensor and engine problems and legal issues with it , it would be best to just try to upgrade to 3" straight pipes ?

This is a cut out.

http://www.jegs.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10002&storeId=10001&categoryId=21295&parentCategoryId=11529&langId=-1

It will go anywhere you want it. they dont sound very good though, its just raw exhaust. the loudest you can get would be- 3'' pipe, headers, w/o cat. Now, a better way would be- headers, 3" pipe, cat (the cheap universals flow pretty good and do NOT hinder the sound), tips. you can get resonated tips (glasspacked tips) for a better sound, not louder, better sounding.
I ran headers, cheap cat, straight 3" pipe for a while and i took it off because it was too loud and it had no tone. Now I have headers, the cheap cat, split dual 2.5" pipes after the cat and resonated tips. this is loud, but it also sounds nice.

Remember, if you run w/o a cat you will loose low end power!! And if you get pulled over and he checks your exhaust you will get a large fine. I highly recomend that you pick up a cheap universal cat they flow better and sound better than the stocker.
hope this helps

sub006
01-14-2006, 10:56 PM
I ran my '90 Suburban for over 350,000 miles with the cat, Gibson 26" muffler and single 3" exhaust.

When I installed my new 383, I added smog-legal Edelbrock headers, fabricated my own smooth-bend y pipe with O2 bung, enlarged the last two feet of pipe to 4" stainless tubing and finished off with a 5" stainless tip. LOUD and powerful sound. Smog-legal in California, too.

LOUD-ASS-SIERRA
01-15-2006, 12:57 AM
that's insane... i gotta see this...i applaud you too.. just wondering, where in the hell did you find 5" inch tips with a 4" inch inlet. Sounds like a sweet ride..

sub006
01-15-2006, 03:41 PM
My five-inch polished stainless tip is designed for DIESELS. I bought it for less than $50 from Bakersfield Van & Trucking in Bakersfield, California.

No local muffler shop could bend 4" tubing. Some had regular quick-rusting steel (not even aluminized) for cutting and welding up RV and HD truck exhausts, but I had my heart set on stainless.

Dick Guldstrand, my Corvette tech, referred me to Jack Burns at Burns Stainless in Costa Mesa, California. This firm makes pre-bent stainless pipe and custom exhausts for NASCAR and Formula I teams. I went in and asked for a two-foot length of 4" with a 90 degree bend in the middle. He handed one to me off the shelf and said "$82". Then I asked him for a stainless 4" to 3" reducer cone and he said "Give me five minutes". He formed it on the spot!

If you look closely at my previous post, you will notice I mentioned a "y-pipe" and one tip. I have a very efficient SINGLE exhaust system; it still has a high-flow catalytic converter. If you live where smog laws are lenient, your duals will be even louder. Because my pipe shoots straight out to the side behind the rear wheel on the driver's side, I set off car alarms everywhere I go, especially cruising slowly through parking structures.

Another thing, if you run 15" rims right next to the 5" tip, they look kind of dinky!

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