Impact of removing catalytic converter - Fuelly Forums
Go Back   Fuelly Forums > Fuel Talk > General Fuel Topics
Search Today's Posts Mark Forums Read
Thread Tools Display Modes
Old 06-16-2008, 05:14 AM   #1
Registered Member
Join Date: Jun 2008
Posts: 38
Country: United States
Impact of removing catalytic converter

I am considering removing the CC on my Mits 2004 Galant.

Good news is that I live in a state that has no emissions checks so I don't have to pass annual emission tests.

I am interested in what are the technical hurdles of doing this?

I want to just pipe it straight through and of course hold on to the CC in case I need to replace it in the future.

If I yank it out of there will the ECU start to complain?

Has anyone pulled theirs out? What is the increase in mileage?

Any thoughts feedback or suggestions are appreciated.

joeventura is offline   Reply With Quote
Old 06-16-2008, 05:31 AM   #2
Registered Member
Join Date: Apr 2008
Posts: 1,090
Country: United States
I wouldn't for at least two reasons.

$2500 fine for violation. Doesn't require an smog check just a visual inspection.

Your emissions system may have a sensor after the cat and if you remove the cat you may get a check engine light.

It won't make any difference in mileage unless its plugged up. If so used ones are not very expensive especially considering your old one has significant scrap value.

Dont know your mileage but your emissions system is covered by a mandatory 5 year 50,000 miles federal emissions warrantee.


R.I.D.E. is offline   Reply With Quote
Old 06-16-2008, 06:33 AM   #3
Registered Member
GasSavers_BEEF's Avatar
Join Date: Apr 2008
Posts: 1,831
I have heard of people gutting their cats for power. that is they just run a pipe through it with a sledge hammer. that way it is still physically there.

not sure if that will help with FE though. I guess it will be less restriction in the exhaust but I still think it will be minimal.
Be the change you wish to see in the world
--Mahatma Gandhi

GasSavers_BEEF is offline   Reply With Quote
Old 06-16-2008, 09:44 AM   #4
Registered Member
vxdude's Avatar
Join Date: Feb 2008
Posts: 93
Country: United States
Send a message via Yahoo to vxdude
i did this mod with my subaru wrx gutted the stock up and down pipe, I definitly felt more power and more mpg. I am able to hit 32mpg at 55mph and almost at 300 horsepower
vxdude is offline   Reply With Quote
Old 06-16-2008, 10:03 AM   #5
Registered Member
ShadowWorks's Avatar
Join Date: May 2008
Posts: 172
Country: United States
My brother removes his CAT after the emissions test every year, he can get 320 miles in the FWY from a tank of gas with the CAT and 380 with it removed, more power means more FE.
Water is fuel, I just don't know how to make it work yet.
ShadowWorks is offline   Reply With Quote
Old 06-16-2008, 10:34 AM   #6
Registered Member
palemelanesian's Avatar
Join Date: Apr 2013
Posts: 364
Country: United States
I can go 700 miles on a tank with my CAT in place.

And then there's this:
1 hp gain over stock (151 vs 150) with a high-flow cat
2 hp / 1 tq gain over stock (152 vs 150 / 108 vs 107) with a straight pipe

Hardly worth the effort. Try something like a grill block or higher tire pressure, and some "adjusting the nut behind the wheel" for real gains.
palemelanesian is offline   Reply With Quote
Old 06-16-2008, 10:40 AM   #7
Registered Member
Join Date: Jun 2008
Posts: 38
Country: United States
PaleMelanesian - thanks for the comments,
I have already tried everything you suggested with a great deal of success.
Now looking to tweak further
joeventura is offline   Reply With Quote
Old 06-16-2008, 04:45 PM   #8
Registered Member
GasSavers_JoeBob's Avatar
Join Date: Oct 2007
Posts: 698
Country: United States
I tried this about 15-20 years ago with my '79 Chevette. My problem was that it only got 20mpg (maybe up to 22) no matter how I drove. Easy on the gas, romping on it, city, freeway, didn't matter. I poked at that car for almost 200k miles trying to figure out what the problem was. One of the things I did was remove the cat...actually ran straight piped that tank. Only result was a headache from the noise and a stern look from a deputy sheriff.

The cat's there for a a kid I grew up in Smoggy LA...sometimes in the summer, especially back in the '60s it got pretty much impossible to get a deep breath! I appreciate anything which helps get the crap out of the air!

If your cat's plugged, you'll KNOW it! The car will just have no power. Discovered this on the way to work one morning...climbing my steep hill (1.8 miles to gain 800 feet altitude) in my Lincoln...suddenly had no power at all, but the car sounded OK. Everyone passing me (my boss gave me a strange look!). Crested the hill and was able to go fast again. Just couldn't accelerate.
"We are forces of chaos and anarchy. Everything they say we are we are, and we are very proud of ourselves!" -- Jefferson Airplane

Dick Naugle says: 1. Prepare food fresh. 2. Serve customers fast. 3. Keep place clean.

GasSavers_JoeBob is offline   Reply With Quote
Old 06-16-2008, 05:38 PM   #9
Registered Member
kamesama980's Avatar
Join Date: Nov 2007
Posts: 742
Country: United States
Location: Columbus, IN, USA
Send a message via AIM to kamesama980 Send a message via Yahoo to kamesama980
on that new of a car, you'll gain little to nothing from removing the cats. power/FE gains are most noticeable in turbo engines and cars at WOT. hypermilers rarely if ever enter the range where losing the cat improves the situation (high revs high throttle). that being said, every engine/car responds differently.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
kamesama980 is offline   Reply With Quote
Old 06-16-2008, 06:02 PM   #10
Registered Member
GasSavers_maxc's Avatar
Join Date: Apr 2006
Posts: 166
Country: United States
You Will F- Up That Car Very Bad If You Remove The Cats!!!

less lurking and more working
GasSavers_maxc is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
An idea for something new. DTMAce Fuelly Web Support and Community News 2 11-30-2009 01:55 AM
Rex-O-Saurus One Year Later mrmad General Fuel Topics 8 03-14-2008 03:55 PM
'93 Chevy 2500 4x4 + Trailer: Help! rh77 General Fuel Topics 9 09-15-2007 08:31 AM
Grand Caravan Grill Block popimp Aerodynamics 39 06-20-2007 04:44 PM
Bike car video kickflipjr People Powered 7 12-16-2006 09:02 PM

Powered by vBadvanced CMPS v3.2.3

All times are GMT -8. The time now is 10:00 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.