1SlowHoe

iTrader: (28)

I wouldn't gut mine because I've never seen any real results posted here or anywhere that says it does any good. I hear if you take a nice big hole saw and a drill you can make them flow real nice

AintNoHo

My Catco cat broke and clogged, so I gutted it. I bought a new one and welded flanges on both ends of both cats and the exhaust pipe. Now, I can quickly bolt in either. It flows a lot better with the gutted cat and you can feel it with the butt-dyno. Unfortunately, it is loud as hell under moderate throttle, not so bad at idle. I think the stock cat flowed better than my "high flow" after-market cat and I should have kept it.

99kon

iTrader: (6)

It sure does mean something in California!!! That is the wrong way to prove your point "it dont mean ****". They have some of the stricter laws about emissions. When you put 500HP threw emissions and pass is something to be proud about. Im going to do what AINTNOHO did and just cut the cats off and weld flanges on them, I love the loudness that no cats bring but i also have two kids one 2y and the other 3m.

Thanks alot for the info!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

w41quad4

Your trying to compare two different things. Performance and emissions, i'm talking from a performance standpoint. As for emissions pumping 500hp worth of exhaust gases through a stock cat isn't a good thing, if your soooooo worried about passing emissions put in a high flow cat with a much larger surface area catalyst and then look at your emissions outputs compared to a stock cat. A stock cat can only catalyze so many molecules when its confronted with too many CFM than it was originally designed to handle.

hog

"Running over 500hp through the stock cats doesn't mean ****"
Actually thast quite an acomplishment for a setup that was put together by a guy who put the combo together himself, not so big a deal for GM with their ZO6 Vette.

If it passes California emissions testing its pretty clean bud. 100 times cleaner than a Quad 4 with no cats. As long as backpressure isnt high, which it isnt, even with his Whipple blower, there is no reason to add a hi flow cat if the truck is passing the tests as is.

"pumping 500hp worth of exhaust gases through a stock cat isn't a good thing"

James is running the dual cat stock Vortec 350 system, he has chopped off the stock inlets and outlets and is now running dual 3" inlets and outlets on his cats. Running 500 hp on a STOCK shortblock Vortec 350 IS quite the accompishment, having it pass Cali emissions is even more of an accomlishment. I have seen James's emmisions printout, its VERY clean.


Congrats James, 500 hp while being clean, it would be nice if more people ran cats, our atmosphere might be a tad more breathable for our Kids Grandkids.
AHHH but who cares, I'll be dead by then, besides I want that extra 3-4 hp in my 5000 lb NA truck.

My truck actually runs better with my dual 2.5" cats, it smells a whole heck of a lot better also. More low-mid rpm torque wit the cats, at least when compared when not using a muffler. I am up for emissions testing this March again

Hog

$thatguy$

iTrader: (5)

why the hostility in this thread ... i took my cats off and im running a magnaflow oval case muffler and stock manifolds and my **** pops and is raspy and i was disappointed when i heard it

w41quad4

There wasn't meant to be any hostility, all I was saying from the beginning that there is power to be had from less restriction due to the catalytic converters. I'm sure if in his 500hp setup he removed the cats he would see some gain.

BTW- I've run a Quad 4 without cats and even had it pass Cali. emissions without any problems when I sold it to a Cal. local.

James B.

iTrader: (1)

Actually, I've had the cats off. I have run both gutted oval-body (unintentionally due to Magnaflow failure) and straight-pipe sections to run after removing the Magnaflows. I was hoping the stright pipes might cut down on the rasp and hollow resonance perhaps being produced by the cat chambers. The straight pipes did't help, it still sounded obnoxious with even a pair of 5x11x22" mufflers. Pipe size has a lot to do with the sound and I have to run the big stuff for the boost unfortunately.
After refitting the stock round cats with 3" inlets and outlets I bolted those inplace of the straight pipes. Sounds much better no, now resonance, no rasp, and it's quieter.
With the factory cats and the above mufflers it is STILL not quiet enough for my taste. I don't want to have to look around for what attention I might attact before I mash the gas. I like stealth and I like it smooth and quiet inside.

I have some videos that might help give you some idea about different exhaust configurations on the same engine sound like. Go easy on the downloading please, I've only got 768kbit up.

OUTSIDE:

1. Idling - stock cats with dumps only, no muffler(s).
http://bertok.us/pics/cats-only.mpg

2. 60mph pass at WOT - Stock cats, Gibson Dual Sport cat-back
http://bertok.us/pics/9psi-heads-cam-flyby.mpg

3. 60mph pass at WOT - Magnaflow cats (new), dual 5x11x22" Mag. Mufflers, all 3"
http://bertok.us/pics/flyby3.mpg

4. 60mph pass at WOT - same as above but no cats now. Sounds like ****
http://bertok.us/pics/flyby4.mpg

5. Launching from stop (far) - stock cats, Gibson Dual Sport (dual 2.25") bolt-on cat-back
http://bertok.us/pics/Launch4.mpg

6. Launching from stop (close) - stock cats, Gibosn Dual Sport cat-back, etc.
http://bertok.us/pics/takeoff.mpg

INSIDE:

7. Stock cats, Gibson Dual-Sport cat-back.
http://bertok.us/pics/0-60.mpg

8. Magnaflow cats, Dual Magnaflow 5x11x22" mufflers, all 3"
http://bertok.us/pics/0-80.mpg

9. Stock cats, Dual Magnaflow 5x11x22" mufflers, all 3"
http://bertok.us/pics/converter.mpg

10. Cats only, no mufflers
http://bertok.us/pics/4L80E-merge2.mpg


From this mess I liked the quietness of the Gibson stuff the best, but it was way too restrictive sounding like the business end of a leaf blowerin the upper RPMs at WOT.

I like the tone of the Magnaflows (deep, low) but not the decibel level - too loud.

I like the stock cats better because they eliminate more raspiness in the exhaust.

I can't stand anything with cats and/or without mufflers. I have driven the truck at WOT with no cats or muffler, just dumps. The novelty wears off in about one second.

When I replaced the pipes sections in the dual 3" system with the refitted factory cats, I lost nothing in top end.

Kon, I hope some of this helps you make your own decision.

1SlowHoe

iTrader: (28)

I definitely like the sound of the Magnaflows WITH the cats. I was debating on getting high flows or staying stock. After reading all this I will keep the stock cats and add another Magnaflow when I do the pacesetter LT's.

99kon

iTrader: (6)

I have already made the decision to keep the cats. The only thing i will do is what you did and flange my cats that way I have the best of both worlds. Like i said I love the loud noise but I have two kids. Thanks for the help.

Hey quad4 never said anything about performance, I know that if you have less restictions you will run alot more HP. I just think its quite an accomplishment that you can run those #'s without spending $40k on a z06 or $80k on a viper. I have a 79 malibu with 600HP (carburated, no cats) and it would never pass emissions, even if i tried to bribe the guy. The reason I ask is because i have never really worried about emissions. Good thing it is considered a classic know.