Gutting Catalytic Converters

[Vettelt193]

to add a bit, the reason why the '93 is the last year of easy cat removal is there is no O2 sensor after the cats.... the car is blind to what goes on after the cats whether they are there or not.

Does that make sense? Again, not trying to flame ya in any way, shape, or form... there are so many variations of C4 even, that it is tough to figure out what will affect what on different years:confused

 

[brimis]

I used a spade bid to drill out the contents of the cat. It took my about an hour to complete the entire job.

 

[Mad-Mic]

i went from 14.4's on average to 13.7 on average when i gutted my cat and removed my mufflers and added a non pre-cat front Y pipe. the times backed it up in a 2 week period back in last september.


you can still pass emmisions with out cats in MD. as long as the skeleton of the cat is there they will not question it. as long as the car is properly tuned and the water and oil temp is HOT when you run it thru it will pass. the hydro carbons will be on the edge but still will be good enough too pass for MD standards.

what sucks about this whole thing in MD is LT and LS based cars with OBD II use LT/LS edit and remove the emmisions codes so when you go thru emmsions all they do is hook up to the ecm and look for codes. no codes you pass. are these cars legal? hell no! straight 3" exhaust from the headers back. O2 sims go in the back of the cat if memory serves me right.

once you run a high lift cam (over the .550" range) the car will most likely not even pass anyway cats or no cats.

i'm sure my lawnmower puts out more emmisions more than my weekend a few days a week vette i drive does. look around you and look at the diesel trucks that pour straight black smoke. diesel supposedly burns cleaner but give me a break! there is no way in hell straight black exhaust burns cleaner then a well tuned non-catted car! look at the factories that pollute the air 1000 time worse than all the cars in that city. it's a money thing and thats all it is and ever will be. Big business always wins out over the little guy.

 

[Vettefan87]

Yes that is the way it works the little guy gets the shaft, while the big businesses get breaks because they are lining politicians pockets with green.

 

[firedawg]

Hey Mic, I take it your emissions test went well? :L

 

[ShaneL]

Just installed my off road pipes and I got the error code P0134 which narrows it down to maybe a loose connection on the drivers side pre cat sensor (I may have swapped it with an unheated sensor but I have no way of telling if all of them are heated or not or if I just did not put it in far enough. Anyone have a cure for this error code? I may just replace it with a new one just to be sure.

Are all of the sensors heated?


(off topic)


HAHAHA I just love to hear people complain about the big companies that nitpick about so many things that don't ever have any kind of effect on their business. And lo and behold they try to slap a restriction on what we can and cannot do just so they can make a few more bucks. Even the idiots in some of the larger companies deporting so many jobs to developing countries where labor is so much cheaper while making us hard working americans suffer by the decreasing value of the dollar.

 

[SQLDBA]

I know that with a cat or not when your AFR is 14.7 or a little leaner you pass in TX. I'm not sure about running richer than 14.7 but I would think that running richer and burning more fuel than stoichiometric would make you fail. It's my understanding that all the O/2 sensors do is tell the ECU what the 0/2 voltage is to allow it to adjust your fuel trims so it can keep your emissions at a 14.7 AFR.

As long as the car is properly tuned then I dont really see a problem because a properly tuned car is probably letting off much less harmful emissions then a brand new car right off the dealers lot. Not being able to use an SAFC to lean out my engine for emissions is probably the one thing I will miss from the import world. :eyerole

 

[-=Jeff=-]

I hae been running with no cats for the last 3 years. I am installing them this year, Mainly to cut down the interior resonance of my B&B 3 Exhaust.

I bought a pair of 3" metallic Cats from Dynatech. The flow is some where between 550 and 600 CFM each. I think those out flow a 2.5" exhaust pipe of the same length, so while the Cats could be limiting my flow, it will not be that much, as the rest of the exhaust is 3" anyway

 

[sothpaw]

Southpaw,
Do you still have the cats on your car? did you do anything else special to pass?

Yes, I still have the stock cats and stock headers--car is as completely street legal as they come. No, I did nothing else to pass, engine was cool (190 oil).

Mic is wrong one one thing--my cam has .566" lift with the 1.6 rr's installed, and the car passed. The computer program in the ECM is not even guaranteed to pass.

 

[Mad-Mic]

Hey Mic, I take it your emissions test went well? :L

going monday will let you guys know what happens

 

[Mad-Mic]

Mic is wrong one one thing--my cam has .566" lift with the 1.6 rr's installed, and the car passed. The computer program in the ECM is not even guaranteed to pass.

some will some won't depending on the tune. once you add a bigger lift cam that means more fuel to the equation thats why most say after .550" lift your on the border line of passing.

my A/F was 12.9:1 i was fighting a rich condition with the car in stock trim. although i didn't have the # for the stock trim A/F ratio there are things you can do to lean it out more with out a AFPR. what i did was over gapped to .047 while indexing the plugs with cut back AC Delco plugs. added more timing and of course made it breath better with a K&N filter, cut box, long tube headers, gutted cats and no mufflers to hold back pressure which results in stored back pressured unburnt fuel. as we all know our cars come from the factory real rich and running hot. hot is good for emmissions but bad for HP. running rich is good for engine longevety.

 

[SSTibet]

Question to Mad-Mic...

MAd-Mic,

You have written that you are running with gutted cats for the last few years. Did you get SES light after the gutting? And if you did get the SES, how did you fix it?

Is it necessary to install O2 SIMS after the gutting for the engine (LT1, 95 Vette) to run properly for an OBDII car?

And if the car is OBDI (single O2 sensor per side), do you still install O2 SIMS in place of the O2 sensors or do you simplye replace the O2 Sensors with new ones???

 

[SQLDBA]

SSTibet,

I've always loved the comp yellow c4's. Nice car.

They have emissions in Turkey, too?

 

[-=Jeff=-]

MAd-Mic,

You have written that you are running with gutted cats for the last few years. Did you get SES light after the gutting? And if you did get the SES, how did you fix it?

Is it necessary to install O2 SIMS after the gutting for the engine (LT1, 95 Vette) to run properly for an OBDII car?

And if the car is OBDI (single O2 sensor per side), do you still install O2 SIMS in place of the O2 sensors or do you simplye replace the O2 Sensors with new ones???

the 84-91 VEttes had only one sensor needed to operate properly, with or without cats. I have been running my 89 without cats for 3 years with no codes.

For OBD II there are 4 sensors, the 2 int he pipe before the cats need to be used, the 2 in pipe after the cats can be replaced with simulators, but if you truly have OBD II (which I don't think is the case, but I could be wrong) you would get a code for the O2 sensors behind the cats as they will register wrong and show a fault in the ECM.

It is also good prctice to replace your O2 sensors every couple of years anyway.

 

[C-4 Now]

I've been running my 89 with cat gutted for about 3 years when it plugged. I think i will install a high performance cat because the poping in the exhaust is annoying when you downshift. Anybody else have experience with this problem? I have never had any engine trouble codes since doing this. Thanks for any help and curiou what others have done in high performance cats especially since i'm looking at upgrading the motor!!

 

[-=Jeff=-]

I've been running my 89 with cat gutted for about 3 years when it plugged. I think i will install a high performance cat because the poping in the exhaust is annoying when you downshift. Anybody else have experience with this problem? I have never had any engine trouble codes since doing this. Thanks for any help and curiou what others have done in high performance cats especially since i'm looking at upgrading the motor!!

I will let you know on the High perfomance converters. I will be installing a pair of 3" Bullet cats to try to tone down the resonance in my vette, right now I have Full length headers and a B&B catback. I will replace the B&B resonator with Dual 3" cats and an x-pipe

 

[Mad-Mic]

well since i run no mufflers they gave me a extention till october to get them so they can hook the sniffer up i was ready though 220+ water temp, retared timing, and a bottle of 90% isopropyl alcohol. who knows by then i might just throw a racing cat on it just too check the #'s although i'm sure it will pass. just making some mental notes due to the new setup going in next season.

 

[SSTibet]

SSTibet,

I've always loved the comp yellow c4's. Nice car.

They have emissions in Turkey, too?

Thanks for the compliments for the car and its color. I couldn`t agree more with you for the color - yellow makes all sharp corners of the car to show smoother than they really are. I have seen C4`s in black and red colors and they not as smooth. I was really lucky to find my Vette.

Yeah we have emission tests in Turkey too, but a lot more `relaxed` than USA of course. I had my road test done last year without ever taking the car to the test facility... Find the right guy and pay him a few bucks and here goes the test; you know what I mean...

 

[WhalePirot]

The later cars, with 'dual' O2 sensors use the first for ECM (engine) fine tuning and the second sensor for keeping track that the CAT's operation is acceptable. I cannot define acceptable.

Earlier cars, like mine (set up to look like an '87, but running a '90 speed density ECM) only have the 'first' O2 sensor. I also changed to the heated type.

The popping sound, is unburned fuel exploding in your exhaust. I get a small amount of it, but you might wish to check your chip's adjustments to the fuel tables for a rich condition. My chip is very, very good, but might not be perfect in the decel area.

No flames; no pains.

 

[invinceablevett]

Just my .02 cents if I may.I gutted the cat in my 1987 trans-am GTA with the 5.7 litre(350).It was just 2 years old.I did not find any "performance" enhancement even though it was faster than other 5.7 litre automatic trans-ams.Some people back then told me that it actually may have made my car slower. ...........I did however have a peculier smell of cooling fluid......Back then I had made just a few mods....air-foil,performance termostat and "powerchip".So I can't really say what it was that actually made my car a little quicker.......My guess is that the smell had something to do with the termostat.