Anyone gut their catalytic converter?

[Killa-Cotton]

Looking for advice from anyone who has removed or gutted their catalytic converter. Did you have any problems (CEL lights, etc.)? I know most of you are in inspection states but I'm in Alabama and we don't have emission testing so maybe there is someone in my area who has done this.

 

[DC runner]

Oh Alabama, always 10 years behind the times.

Yes, if you gut the CAT, you won't see an increase in power. Your trucks engine has been designed to run with it. Contrary to urban myth, gutting it, is not some super power move.

Honestly. There is no reason to gut it. Save the world, a bit, and it will keep your engine running as designed. If you get to the point where it is clogged... then you can cut to your hearts content.

It will pop codes. Your downstream O2 sensors will register the exhaust as incorrect and will attempt to adjust the combustion cycle to make up for it.

EDIT: Also, Alabama isn't far from requiring emission testing. Multiple counties in that state are now failing clean air standards and will start moving toward active measure to reduce pollution... emission testing is one. So, I wouldn't destroy your cat yet... you may need it.

 

[Nelsonmd]

Does no emissions testing mean you don't even have to get a safety inspection? All vehicles newer than 95 have OBD that performs the emissions test itself, so the safety inspection includes a check for a CEL, and if there is one, you don't pass. I would imagine AL does check for CEL's.

Anyway, yeah, don't gut it. If it really does clog up, then just replace it with a cheap aftermarket one. They aren't that expensive, and it is alot better to run with a cheap one than run with a gutted one. I'm no tree hugger, but you shouldn't go out of your way to pollute.

Also, gutting the CAT will not affect your combustion cycle. You may not have the right backpressure, which can affect performance, but the downstream O2 sensor only throws codes, it doesn't affect your A/F mixture. The front (upstream) O2 sensor (which is really an A/F sensor) affects engine performance.

 

[DC runner]

Really? I thought that they all sent info to the ECU and it adjusted, but I guess that makes sense.

Front O2s send cycle info.

Anyway.

 

[Stick Figure]

Gutting it will actually generally hurt performance just for the fact that you now have a huge empty chamber for the exhaust gas to lose velocity. If you truly want to get rid of it replacing it with a straight pipe would be my suggestion.

On an NA truck, I really don't see the point though. If this was a boosted monster that you took out on weekends to play, I would probably say go for it, but on a stock vehicle if functioning correctly I wouldn't waste my time to get rid of it.

 

[LDForget]

You will get a b1s2 low catalyst efficiency high voltage check engine light. It wont effect your air/fuel ratio but it will in fact decrease back pressure which is actually required for efficient scavenging. If you dont know what this is, then dont gut/bypass your cat.

 

[Speedweigand]

Really? I thought that they all sent info to the ECU and it adjusted, but I guess that makes sense.

Front O2s send cycle info.

Anyway.

The rear o2's look to see if the catalyst is working, which is why OBDII vehicles throw codes when you tamper with the cat.

If you truly have something against cats you'd be much better off replacing it with a straight pipe. I have seen many a car lose hp on the dyno from gutting a cat. The first exhaust pulse that enters the cat rapidly expands to fill the cavity, the second pulse gets pushed through the center of the first and so on, first in last out kinda deal resulting in lots of turbulence inside the exhaust, effectively slowing it down and robbing power.

Normally when installing a hiflo cat on a straight piped racecar the hp would drop 1-2whp, however there would almost always be a torque gain of 2-3ft-lbs.

The cat straightens the exhaust pulses a little and results in a mellower sound too, if you've ever cut one off you had to notice a raspier, cackley exhaust note.

 

[Wallawalla0117]

I straight piped my clogged cat, then the nightmare began

Alright I apologize for the long post. I just joined and cant start new post yet but this kinda seemed to fit here...
So yeah my 98 4runner had a clogged cat which I cut out and replaced with a straight pipe. Was just planning as temp fix till I replaced with aftermarket cat. About a week or so after, the check engine light popped up sayin something about the catalyst system not working I can't rememebr exact code but I didn't think anything of it.
So then about another week after the light turned on I was parked idling in my driveway and the engine just gently turned off. No struggling no chugging just poof* dead. So tried starting back up but it would crank for a second then stop. Crank for a couple seconds then stop. Installed new starter and now will crank and crank with no start.
So then started the obvious checks for fuel, spark, air...replaced my old battery and have 12 volts at the fuel pump, thr pump buzzes when I connect battery directly to it. I verified spark. All fuses and relays are good. I checked the timing and everything is still good. The crankshaft timing gear still has all its teeth. Then I noticed I wasn't getting any rpm jumps while cranking. So I ordered a crankshaft position sensor and waiting for it to come tomorrow. I took out the one I have and bench tested with multimeter and the ohms are in spec and it registers voltage when getting close to anything metal so I'm not sure how else to diag if the sensor is bad but the replacement is on the way.
SOOO... could the straight piped, non cat have anything to do with my engine just dying and now not starting? Also any further suggestions would be extremely helpful. Im just about out of ideas if the crank sensor doesn't solve it. Thanks and sorry for not starting a new post.

 

[Wallawalla0117]

I guess I should have added it's a 1998 limited automatic rear wheel drive

 

[gamefreakgc]

Alright I apologize for the long post. I just joined and cant start new post yet but this kinda seemed to fit here...
So yeah my 98 4runner had a clogged cat which I cut out and replaced with a straight pipe. Was just planning as temp fix till I replaced with aftermarket cat. About a week or so after, the check engine light popped up sayin something about the catalyst system not working I can't rememebr exact code but I didn't think anything of it.
So then about another week after the light turned on I was parked idling in my driveway and the engine just gently turned off. No struggling no chugging just poof* dead. So tried starting back up but it would crank for a second then stop. Crank for a couple seconds then stop. Installed new starter and now will crank and crank with no start.
So then started the obvious checks for fuel, spark, air...replaced my old battery and have 12 volts at the fuel pump, thr pump buzzes when I connect battery directly to it. I verified spark. All fuses and relays are good. I checked the timing and everything is still good. The crankshaft timing gear still has all its teeth. Then I noticed I wasn't getting any rpm jumps while cranking. So I ordered a crankshaft position sensor and waiting for it to come tomorrow. I took out the one I have and bench tested with multimeter and the ohms are in spec and it registers voltage when getting close to anything metal so I'm not sure how else to diag if the sensor is bad but the replacement is on the way.
SOOO... could the straight piped, non cat have anything to do with my engine just dying and now not starting? Also any further suggestions would be extremely helpful. Im just about out of ideas if the crank sensor doesn't solve it. Thanks and sorry for not starting a new post.

Straight piping will throw a check engine light but won't kill the engine. Before you spend any more money, clean your Mass Airflow Sensor with carb cleaner/sensor cleaner. You'll want to look inside the unit for hidden little wires, they are really tucked in there. Replace your air filter as well in case it is clogged. See if that does it.

 

[Devbot]

If you wanna get rid of that CEL (I imagine it's p0420) you'll want to use an O2 spacer.