This crap has been debated endlessly.

Blows my mind how selfish people can be for a few HP (at best) & sound. Probably use these stinkboxes as daily commuters sitting in stop & go traffic too.

The stink is horrific, and as for sound diff...

I hope they get ***-packed when their resale/smogs come due.

And for the guy claiming "huge improvement in drivability" by removing the cats... WTF!?!?

Time to get another tuner, there buddy.

 

Are you Asian?

I've got a vert and I decided to keep my cats since I've read that it's worse in a vert.
I think I'd gain a whole lot more than 5 hp and a ton of bottom end but at this point in time I choose to not smell like gas every time I drive the car!

 

I know LT's are'nt CARB legal here in Cali, I guess because relocating the Cats is illegal. My question is , having hi-flow cats installed,will that be good enough to pass the sniffer test? If not, what would I need to have to make a LT setup blow clean enough to pass the electric nose?

I know that LT's won't pass the visual, but sometimes there's a chance they won't be spotted.....All I want is my LS2 to have the same performance as the new LS3...

 

Yes, the HF cats will cover you on the sniffer test.

Many other things you can do to your LS2 to bring it up (and well over) to LS3 specs.

Get a tune would be the easiest & most cost-effective.

Robert at Advanced Dyno is Suisun is worth checking out.

 

Global warming? This has nothing to do with global warming.

We're discussing it here because it's here that the question was asked "any problems running without cats?"

 

When I installed my headers, the cats (X-pipes) came 2 weeks later. I did not want to wait. Yes.. the Billy Boats DO bolt straight to the H-pipes. The check engine light came on within 2 minutes. Yes, the smell is worse because the hydrocarbons STINK. The sound is a cool sound though....

just a note... we have emissions testing here. I have a Ford 302 in a jeep with custom fenderwell headers. i "CAN" pass emmisions without the cats, but its is via a retune. SO what I have done, is just remove my mufflers from the end of the headers and put on cats with the same bolt up flange to the headers, and just go with them for emmisions. It lowers the hydrocarbons by a factor of 10.

 

It's a Federal offense. Illegal in all 50 states.

 

Nanny Nanny Boo Boo

 

I have both catted and off road x pipes for the turbo Mustang and run cats most of the time because I can't stand the smell when not running the cats. I have dynoed the car with and without the cats and could not tell the difference all motor. On nitrous or with the turbocharger, I can't tell you, but the cats on the BBK h-pipe have worked great for years.

I put LG long tubes with cats on the C6 Corvette because I have not had any problems running cats on the hot rods. As long as they don't create any problems, they stay, but this is an easy decision since the car is a street/trip car, not a drag race car. I will change them out if and when they fail to reduce the hydrocarbon emissions.

We have a '67 Corvette with a carburetor and no cats to remind me of how far we have come in 40 years.

I vote for running cats on a street car, headers and all. I don't think headers which will allow you to keep the factory cats is going to provide much of an improvement power wise, so I think you are stuck with aftermarket cats further away from the engine cylinder if you want much benefit from the headers.

Joe

 

Maybe I should have phrased my question better.......it has nothing to do with gaining a few hp (I think the gains would be small.....no cats vs. hi flo cats). I asked because I know of several people that have blown the so called hi flo cats out (different brands) in a relatively short time (especially on a forced induction car). I have been on this forum for a couple of years, and have seen very little discussion about not running cats. I asked because I wanted to know what the effects would be. I'm also amazed at the disparity between answers (from no smell to smells so bad I can't hardly drive the car....how could there be such a difference)? Pls keep the advice coming.........but PLEEZ people.........calm down.

 

I took the cats off both my last C5 and my C6 Z06. On the C5 there was a smell. On the C6, no smell. Go figure. My only guess is the C5's aftermarket cam with more overlap caused it.

 

Some people can't smell very well.

Of course, it can go both ways. Sometimes catalysts + high-sulfur gas will produce a nasty rotten-egg smell that's more offensive than a rich exhaust. But that's pretty unusual.

 

Great, where do you live? I'm going to bring my old motor oil over and dump it into a hole in your yard. You don't mind do you?

$200 compared to $25,000 and possible jail time. Seems like an easy decision to me.

 

Some people seemed to be consumed with minor environmental concerns. If this is the worst thing we have to worry about the world must be in "GREAT SHAPE". Last time I looked 8000hp top fuel dragsters, funny cars, pro mods and pro stocks don't run cats either. Even though not street leagal...I'm pretty certain the amount of hydrocarbons released are substantial.

 

You are correct. FI motors can "compact" cats, effectively reducing the exit of exhaust gasses while increasing engine temps.

 

Now that's funny!

 

The cam has a lot to do with the unburned hydrocarbon smell.

Bushong572--I guess my point is that I have not ever damaged a catalytic convertor on several power adder cars. It depends on how long the engine is run at wide open throttle at a high exhaust temperature. Since most power adder cars are tuned a little richer than a non-power adder car, the chances for damage due to heat are actually a little less from a temperature standpoint. On any car used for open track events, I would think the chances of damaging the cats are greater than on a drag race car. I've never done anything at WOT other than drag racing, less than 15 seconds, so no damage. But that includes an 11 second nitrous car. Perhaps the guys that do the open road races can tell you whether they have ever hurt the cats or not. I do not turn off the cat overtemp protection on those cars specifically because I wasn't sure whether the cats would be damaged or not. The factory computer will fatten up the air fuel ratio after about 8 seconds at WOT just to reduce the exhaust temp enough for the cats to live. I turn it off on a drag race car, to keep the car from going rich unexpectedly in 3rd or 4th gear. No problems for up to 15 seconds, but maybe for 30 seconds, the cats will heat up enough to cause them to fail.

The cats will fail if they overheat, and they will overheat if the exhaust temp is too high for too long.
How hot and for how long, I can't tell you. The factory engineers say after 8 seconds at WOT, go to about 11:1 air fuel ratio or richer.

Joe

 

Comparing a street-driven car's pollution output to a nitrous dragster is irrelevant, and highlights the ignorant attitude, of "hey, there's much worse pollution sources than me pulling the cats, so what's the big deal?"

Most of the geezers here can't smell and/or hear anymore, and were raised in an era when there was no concept of environmental stewardship/responsibility.

Trust me, the smell is nasty, and spending a day on a drive behind a C6 with no cats, will leave the occupants of the trailing car reeking.

The fact is the cats have a negligible impact in HP/drivability - its been proven here time & time again. Additionally, ~+/-4RWHP on NA cars is well within the tolerance of back-to-back dyno runs, and certainly impossible to notice.

I've had my HF cats (can't remember which brand Kooks uses in their mid-pipes) on for >25k miles & they have not blown out.

Like the above poster said, can I come over and dump my used oil/anti-freeze/brake fluid in a hole in your back yard? That was funny!

 

I'm not going to post what I feel about this at the risk of being removed from the forum, but I will say for certain...one thing I am not is ignorant.

 

If you can't logically & politely express your views without someone screaming "mod?!?!", then PM me - I won't report you.

The bottom line still stands pulling cats yields an insignificant/imperceptible gain on NA cars, and those with FI cars, which yours appears to be, just need to buy quality cats that are designed to withstand the operating parameters of FI engines. Strapping a blower on your C6 isn't a reason to justify pulling cats & making the rest of us choke on your unburned emissions.