Removing the cats gave a boost to my 01 Z06
My only mods on a dyno day a year ago with Mich Forum buddies present were a BPP off-road pipe which eliminated all the cats, and a simple $50 K&N type filter right off the MAF.
My HP was 352, forget the Tq offhand, was close to that.
I gained 23 HP from total stock.
I was stronger than 2 '02 Z06's that were totally stockthat day.
I doubt the cone filter did all that
My own guess from people dynoing with just intake filter changes was that the filter was worth about 8-10 HP, and the cat removal was about 12-14 HP, torque figures about the same, gains were similar across the entire RPM range.
My pipe can come in and out in about 20-30 mins.
Want to help the air?-No wood fireplaces, BBQ's, etc. -preach only if you don't do these things
I'll decide what to do with my cats...

:yesnod:

 

1. Agreed

2. Are you serious????

3. Agreed

 

On a 435 RWHP car, I did back to back dyno pulls (same day) with and without cats. I gained 2-3 RWHP without, but I also gained significant resonance at 1400 RPM, and enough hydrocarbon smell that I have to switch the HVAC to recirculate when I come to a stop.

I have high-flow cats ready to go on.

 

Having read this entertaining and educating thread as it meanders along....
...the end result is
larrysb wins
cats stay in
and I get to drive Suburban, Silverado, Cavalier and vette knowing I am probably going to annoy Tom :smash:

 

Here was my source of information:
http://www.geocities.com/MotorCity/G...emissions.html

The five main emissions for petrol and diesel cars are:-

Carbon Dioxide (CO2)
Carbon Monoxide (CO)
Nitrogen Oxides (NOx)
Hydrocarbons
Particulates

Of these five, a diesel car is better than a petrol car with three of them, about the same with one, and worse with one. Only one of these classes of emissions is visible (particulates, or soot), and rather unfortunately for diesel cars, that is the one which is worse for them. The three emissions for which petrol cars are worse are invisible, so you won't realise that they are there; however they still cause harm to health and the environment.

Nitrogen Oxides


Nitrogen is the main constituent of the air that we breathe. When it is exposed to high pressures and temperatures it combines with oxygen in the air to form nitrous oxides. The nitrous oxides then combine with low level ozone to form smog. Because of the way a diesel engine works, with an excess of air inside the engine (rather than "just enough" as in a petrol engine, which is what causes CO emissions), nitrous oxides are more likely to be formed. However tests of actual cars reveal that whilst emissions of NOx are higher in a new diesel than a new petrol car, that by 50,000 miles or so they are the same, and after that the petrol engine produces more than the diesel. Therefore over the life cycle of the car, petrol and diesel engine emissions of nitrous oxides are similar.

Particulates or smoke are really the only problem for diesels (compared with petrol engines).

Summary

Diesel cars are better than petrol cars with reference to carbon dioxide, the global warming gas.

Diesel cars are better than petrol cars with reference to carbon monoxide, a poison.

Diesel cars are better than petrol cars with reference to hydrocarbons which cause cancer.

Diesel cars are similar to petrol cars with reference to nitrous oxides, which cause smog.

Diesel cars are worse than petrol cars with reference to particulates, which have unproved health impacts.

As Mark Twain once repeated (from Benjamin Disraeli), "there are lies, damned lies and statistics." It is easy - and sometimes even partially truthful - to throw around numbers that SOUND huge, but in reality don't mean much. For instance. What if I made $1 a week and I knew someone who made 100 times as much as I did? They still don't make much.

That is the case with a lot of the emissions now. If a diesel makes 0.4 grams of NOx per kilometer, and the gas engine makes 0.04 grams per kilometer, then the diesel makes TEN times the amount of pollution, but in reality, neither number is a lot.

And those, by the way, are real numbers.
http://www.matthey.com/environment/c...lution/02.html

Maybe it is an age thing. I spent too many years in high school with a 1967 Cougar that had a carbureted, 260 @ 0.50 / .591 lift cammed engine in it, with lots of overlap and probably some pure unburnt gasoline coming out the tailpipes (exaggerating, slightly) to worry about what a closed loop, O2 sensored engine might let slip by without a catalyst.

I just don't think a few thousand guys in Corvettes (or even throw in the Mustangs and Camaros and Firebirds) make any difference in the hundreds of millions of cars on the road, many of which legally have no emissions controls. And of course, there are the SUVs! :)

It's a FEDERAL law, that is pretty obvious. But the reason the penalties are so harsh (although it is almost never enforced anymore) is because when emissions FIRST came out, the car companies weren't ready and emissions controls were HUGE performance drains. The penalties were put into place to discourage MASS removal of the devices. Now, most people don't know or car that they are there. We are a very small crowd in comparison.

Not with our "group size."

Freeing up the exhaust path will improve high rpm hp almost without exception. If you aren't getting that, you need to tune for the new conditions. The hp is there waiting to be had.

That is misleading and ignores most of my points.

1. The cars are still PCM / O2 sensor controlled. The mixture is very near stoich and emissions are GREATLY reduced from pre-1973.

2. There are very few of us who feel any need to remove the cats. We aren't a drop in the bucket.

3. SUV's get to play by different rules. But you don't have a problem with that - why not?

We all break different laws. Some (most) Corvette owners speed, and many have been well into triple digits on public roads. Many have roasted the back tires at some time or another. Others remove cats. We rationalize that the laws we break are ok, but that guy across the street is an idiot for breaking the law he breaks. It's human nature.

Personally, I don't follow your logic. Since SUV's are "trucks," it doesn't hurt the atmosphere if the 60 million plus SUV's on the road pollute a great deal more than the couple hundred thousand C5's. But if a couple of us yank the cats, we are killing the earth? I do not follow.

Sorry this was long guys... I don't know how to post short ones. :D

 

Ok, when the people DEFENDING me admit my posts are long, I gotta work on it!

Me: Hi, I'm Tom and I write long posts.
Long Posts Anon Group: "Hi Tom."

:D

 

Not enough apparently. The best I have been able to do so far, is this quote:

"A new petrol car today produces around 1/20th of the emissions of an older, non-catalyst car."

That is not an easy topic to research. I would say that if that is average, I'd BET that an older Corvette, with a high-performance long-overlap cam would be even worse. Might bring the number closer to 40-50 times as much. So I wasn't off by astronomical proportions. Worst case, I was off by a factor of 5.

And don't forget - it is LEGAL (and available here - albeit expensive) to run LEADED RACE FUEL in a 1967 Corvette. Now I am headed towards that 100 times as much number pretty easily...

I am having a hard time finding any other comparisons of the pollution from an older car vs a newer one online. Anyone got any pointers?

 

Doesn't annoy me at all. I STRONGLY encourage you to do whatever you like!

I don't car whether you drive the Silverado and Suburban.

What would annoy me is if you gave me a hard time for deciding to take my cats off - and then still drove the Silverado and Suburban and acted like you were some saviour of the environment and I was its destroyer.

That would be illogical and irritating! :D

 

Hey Tom Chill
do you assume everyone is your enemy until proven otherwise...
...perhaps not the hydrocarbons emitted from internal combutables but you may want to move a little further from the hydrocarbon emitting pines in your vicinity...
...you allow others to annoy you and that is illogical...

 

With Long Tubes, (LGM) I gained 7 RWHP and 5 RWTQ.
Randy :cheers:

 

I hear ya' ; but whose quote is it... Al Gores? :lol: :p: :)

 

I have thought about this issue for awhile and refrained from putting down my thoughts in this forum until this thread (thus the dam broke forth.....):
I know many of you don't agree but try to get outside of yourself a little and help the environment as best as you can even with all the compromises. but don't rationalize your illegal deed by comparing to the lowest alternative. You would be no different than the industrialists who have influenced the Bush administration with their crying or rationalizations of why they shouldn't follow the law. None of us talk about total performance which really includes how clean a car can run besides how fast it can go. The cats are in there for a good reason and they do work. We all have to contribute as little as it may be to the total picture; try standing at a busy corner. SUVs, just like cars, run quite a bit cleaner than they used to. No, not like cars but then we don't drive vettes for those reasons; we drive them instead of SUVs because they are too big and heavy for good driving enjoyment. You still run "clean" without cats - but not anywhere as clean with cats. The only thing you can control is your behavior - not others. Take the high road and help the world be a cleaner place no matter how little the effort may seem. The tradeoff is such a small price - 5 or 10 horsepower out of 300+! By the way tuners with any brains won't jump in here because it's an illegal activity (pulling cats). (But if they do it's for off-road - uh huh!) OK, I'm off my soapbox. :)

 

I'll be damn, He asked about performance increase and it looks like a conservation debate. Why not just give the answer or results? It seems as though there is more hot air and trying to impress than to just give the answer. Its obvious that it is not EPA compliant but then again was that what he asked? The simple answer would have been to say yes but at costs to the environment. Instead we get bored to death with someone who obviously has more time on his hands than he knows what to do with.

 

Cool. :D

I'm not insinuating anything, but some of the 'vette owner's I've seen spend thousand's of $$$ chasing a fraction of a second - should save their money on car parts and spend it on Jenny Craig. (including me and my fat-assets). Losing 50 pounds of table muscle would probably do more to improve a lot of guy's quarter mile times than anything else. :lol:

 

...hmmmm...I weigh in at 167lbs...that ought to give me the edge over the other guy at 50-150 heavier...
...knowing this...I am still going to leave the cats in and stay lean...
...and race fat guys... :D

 

The only thing you can control is your freedom. Take the high road and do what you want based on your freedoms, and make the world cleaner based on real science... not unproven theories thrown out by the environ-mentalcases holding their hands out for their next paycheck (research grant).

I like my rendition better :)

 

I hadn't thought anyone here was my enemy. You are the first to suggest that.

I only have two pines, lots of poplars and maples though - are they killing me? And, what are you talking about?

Actually, I think that I annoy others more often than they annoy me! :D

 

A very fair reply!

I don't necessarily agree with all of it, and I won't necessarily do all of it, but it is well thought out, and well said and you make some good points!

 

Where's Maineiac at? We need some trees cut down! :lol:

 

Hey Tom, You Da Man! :cheers:

I read somewhere that curtailing the few hi-performance car owners will not do jack for the environment, and come to think of it, of those hi-perf car owners, the number who actually remove the cats are VERY, VERY, few. Better to clamp down on all trucks (light and heavy duty), and especially city buses!