choppin out catalytic converter
- Thread starter gtpinsc
- Start date
98GT3800
New member
Hey i did chop my cat to and i welded straight pipe in place. The good news on my end the o2 sensor is not smack dab on the convertor. So with that said i left mine plugged in while welding and i've been driving if for almost 5 months and not one sign of the check engine light and know it works.
Bad news is according to my Info Center ive lost 5 or so MPG. and little over 100 miles to the tank. Now could this be caused from something else not sure. But I think the car is running to lean.
But let us know
Bad news is according to my Info Center ive lost 5 or so MPG. and little over 100 miles to the tank. Now could this be caused from something else not sure. But I think the car is running to lean.
But let us know
Iron Indian
New member
If you lost MPG you have other problems. Getting rid of a cat WON'T kill gas mileage period, if anything it'll help it anyway. I've removed cats off of 3 cars so far I never lost any mileage, if anything I gained. Thats not true at all.
njbrain
New member
It all depends. Every engine is engineered to have a certain amount of back pressure. If you drop it to far, you will not only lose torque, but also horsepower. When I put a cat back in my car, I gained about 2mpg city, hwy stayed the same.
98GT3800
New member
Well i have chopped plenty in my day to. lol. my dual setup on my old camaro and it runs better than ever. But i'm not sure why ive lost so much, as a matter of fact i was talking to the wife and our van (00 pontiac montana 3.4) She told me she's been running out of gas alot faster to. We use to be able to get 390miles on one tank now shes getting less than 250. Could i just have a string of bad luck im not sure. But no check engine lights or abnormal driving, and no i didnt cut her cat off lol..
Iron Indian
New member
I'll I know is my Black GTP when it had just a CAI and a 3" Off Road DP and actully gained a couple MPG. With a good tune, colder plugs. ILGPC IC, 3.25" it gained a little more. I'd have to figure it up but it gained a good 3-5 MPG than stock.
My car with its mods and 3.29s + 3000 stall still gets better MPG than it did bone stock with over 100,000 less miles...
My car with its mods and 3.29s + 3000 stall still gets better MPG than it did bone stock with over 100,000 less miles...
98GT3800
New member
I'll admit I had my foot in it for the first week and its not that much to brag about now. But could it just be the winter fuel, im not sure if thats even true but my friend said in the winter his toyota gets horrible mileage. Honestly its getting on my nerves now, knowing i was getting 26 mostly on my GT and now close to 15- 22.
try this link from regalgs, some good info, http://www.regalgs.org/forum/viewtopic.php?f=45&t=48704&hilit=catalytic
the previous owner of my car decided to order a dp without a cat but had the second o2 turned off in the pcm. As far as mileage goes, if i keep my foot out of it I can get 26-30mpg depending on conditions.
With your current mods how much boost do you have? Until you find the cat to be a serious enough restriction to be removed,gutted, etc just leave it on.
I have seen sparkplug defoulers used on a 3100 monte carlo. Supposedly it works but the guy also took his cat off for power(because his high mileage 3100 needed it?) and had not changed his dexcool in 5 years...yikes. I believe he blew a head gasket on his trip from stl to las vegas.
on a side note: Tests in car craft magazine have shown high flows used on 500 horse engines to only restrict at a most 10 hp. Same as glasspacks used as resonators, maybe a 2 hp loss.
the previous owner of my car decided to order a dp without a cat but had the second o2 turned off in the pcm. As far as mileage goes, if i keep my foot out of it I can get 26-30mpg depending on conditions.
With your current mods how much boost do you have? Until you find the cat to be a serious enough restriction to be removed,gutted, etc just leave it on.
I have seen sparkplug defoulers used on a 3100 monte carlo. Supposedly it works but the guy also took his cat off for power(because his high mileage 3100 needed it?) and had not changed his dexcool in 5 years...yikes. I believe he blew a head gasket on his trip from stl to las vegas.
on a side note: Tests in car craft magazine have shown high flows used on 500 horse engines to only restrict at a most 10 hp. Same as glasspacks used as resonators, maybe a 2 hp loss.
Last edited:
98GT3800
New member
Well after chopping the cat almost 2 months ago and the mileage going down about 2 weeks ago. The Engine light finally came on today throwing off the o2 code. so i guess im going to have to order the O2 eliminater anyways. Any ideas or suggestions on that. should i get an eliminater to plug or is there a way to by pass...
blueguy
The Blue One
riceburner
New member
brodyman, i do run at bandi when i can. only got the girl up once this season. Im hoping to have both the bird and gtp up next season though.
blueguy
The Blue One
ZZ Performance sells them also. I had one for sale until I actually got off my ass to put it in:th_biggrin2:
rynoman03
I AM PEWPIN!
Meh...my cam hurts MPG
But when I had my 3" Exhaust custom made and my 3" Shorty DP put on (No cat, res., or u-bend) I gained about 4 mpg's...but staying out of it was the problem
I hear that. I get 29 to 31 if I don't romp on it at all. But I just can't do it. I was getting 30 the other day and some ass in a Lexus cut me off while talking on his phone. Plus it doesn't help that I have road rage:th_thumb-down: . I watched my mpg go from 30 to 26 in about 15 second. :th_lipssealed1:
Back to the Catt conversation I went cat less about a month ago and no my car is loud as hell in the cab at certain rpm's. Definitely going to have to get a res or a larger glass pack for resonance.
i went with headers a 8 inch flex pipe and a high flow cat,the rest is stock past the cat,the gov. caught up with casper elect. and those 0-2 sims and fined them preety hard,they found mine while testing for emis. and luckaly the guy was nice and let me go,if you need an 0-2 sim i have mine