ftorsell

that hp can i aspect taking off the catalytic converter :confused:

larrysb

If you've done nothing else to the car, 5-10 at most. Might lose some in fact, depending on what you do.

Not worth it.

ftorsell

i have don a few mods like ati blower, cam, exhaust :rolleyes:

EVIL

does your state inspector do a visual check or a sniff test? if just a visual, why not take them off and knock the honey combs out of them, then re-install them....basically they wouldnt do anything but look like they are there....or you could swap with the z06's and buy a set cheap here on the forum...

STAGED

I think an easy 20 rwhp peak difference (could be more as you can be more aggressive with calibration as boost vs. rpm should drop a touch) if the cats being removed are not clogged. No specific measurements but I bet you I'm close to correct. Throttle response will be snappier. Part-throttle low rpm may seem weaker.

Noise and smell are drawbacks though.


[Modified by STAGED, 4:08 AM 9/30/2003]

EVIL

how is a louder exhaust ever a drawback? :D

larrysb

There's no way for me to know that Karl - I've never seen your car, it isn't in your sig either. (I have that turned off anyway).

What are your laws in Sweden regarding the catalytic converters?

Given the modifications you've already done, you can probably expect 10+ if you have the car tuned afterward to get the fuel trims right. Down side is the smell and increased pollution, hassles with your local vehicle inspections and so on.

The cats have a positive effect on the world around us, since they reduce pollution. If you can see your way clear to keeping them somehow, that would be a good thing.

SleepieAce

Perhaps 10-20 hp. I don't have them on mine. You might also consider some high flow cats if you have to pass emissions. :cheers:

ftorsell

the law in sweden is if you dont have them on your car you have too
pay 1625:- us :sad:

SleepieAce

:eek: :eek: Wow, that sucks! I'd definitely look into the high flow cats. Random Technologies makes a set that I've heard good things about. Might get 10 hp or a little more. :cheers:

BigLew

It will be a lot louder without the cats!! :eek:

FASST LN

The loudness of the vehicle changes as much when removing the cats as it does to remove the muffler. It also makes the exhaust a lot more raspy. The smell will be like you have a fuel leak on your car. If you drive with your windows down, your clothes will smell like a fuel station where ever you go.
I suggest you get some high flow cats and look to gain some more power elsewhere.
I say all of this from experience.

johncazin

Well, it is nice to feel strongly about anything.. but facts are far more powerful weapons.

A quick check of NASCAR, NHRA, IMSA, and F1 finds no converters currently in use- while there are cats that offer very little flow restriction, cats DO alter exhaust scavaging, thus power.

Cats are not an environmental nivana. They are effective primarily in cold engines, and once a well-tuned engine is warm, they offer little value to cleaning the air- I have passed a smog check with my well-warmed, cat-less L98.

I've read about this "gas smell" before, but I have yet to actually witness it.... whereas I can smell one of those older GM cats, no problem- boil me some eggs....

In fact, once you factor in the manufacturing and waste disposal of cats, you can make a pretty decent arguement that cats have a net-zero effect on the environment..... but as with the great freon debate in this country, the real forces that drive this matter are largely financial, not environmental.

Just a reminder- the average forest fire dumps more pollutants into the air than every internal combustion engine ever built has dumped, combined.......

My cats stay off, I sleep at night; Putting the Magnuson on the C5 now, with X pipe and no cats..... I may run up north for a smog check, just for fun.....


[Modified by johncazin, 9:25 PM 10/6/2003]

molon labe

i like this guy, and i suspect that he speaks the truth. :) :cheers:

oh, and i ripped my cats off a couple weeks ago too. anybody who has a problem with it is free to suck some fumes.

leatherbeeC5

Ok I am sorry were we talking about street cars or race cars? Because if we were talking about say a drag racing specific car, then you should definitely remove the cats to minimize back pressure. While you are at it you should remove the exhaust completely and just run open headers! And don’t forget to strip out the interior for weight savings!

Yes catalytic converters do create back pressure! Just like your muffler, exhaust itself, and any bends at all in the tubing create backpressure as well! The fact is we were talking about street driven cars that a moderate amount of back pressure can help with torque thru-out the powerband. I never said that you would see no HP increase comparing no cats to high flow cats. I did say that it would probably be about 10HP at best?

Ok I did also mention that we have made great advances in catalytic technology. So comparing an 85-91? engine (old technology) to a LS1 (97-03) engine is little bit of a stretch. Yes depending on the emission testing equipment, I would say allot of early tuned EFI cars will pass without cats. That is because the emission tests allow for a wide range of allowable emissions based on there inefficient systems (low technology). Now lets take a sequential EFI LS1 motor and remove the cats and take it to a emission tester in Calf!-Lets see if you can pass that test? While you’re at it check out the difference in emissions between the two. Yes you are correct cats will not operate until properly warmed up. Maybe this is why the auto industry spends billions every year trying to develop a cat that starts working quicker. However maybe that is also why they require your engine to be fully warmed up prior to emission testing?

Ok they are certain things in our environment (forest fires, cows farting, people breathing, etc.) that we cannot completely stop. However a gasoline engine puts out other toxins, in addition to the toxins coming from your forest fires.

I am glad you guys that illegally removed your cats are sleeping well at night. Yes that $10,000 fine is no worse than a parking ticket? Because of people like you the government will soon be saying that any Forced Induction device will automatically fail your vehicle even it has no effects on net emissions! However that 5-10HP is all worth it!

molon labe

i didnt illegally remove my cats. we dont have emissions testing in Kansas. in fact, we don't have any inspection at all. they have bigger things to worry about here than the 0.00001% of the population that removes cats.

heck, when i had my c5 on jacks 2 weeks ago, and i was removing my cats, a local cop drove by and saw the car jacked up, and stopped to make sure somebody wasnt stealing my wheels. he came over and asked what i was doing and if i was the owner. i told him about the cat removal, and he replied "cool! that is gonna sound even more wicked than 2 weeks ago when you raced me in my unmarked mustang." :)