Cutting off Converters

[coop]

My brother has a '96 Chevy Silverado Z71. He wants straight pipes with flowmasters. I thought that cutting off the catalytic converters would mess the engine up. Will removing the converters on this model mess the truck up?

-coop

[sxmax]

You would have to make sure you have (2) O2 sensors and even with that you will get really horrible mileage. I know a guy that did it and mileage went from 15 to 5. Ideal setup on that truck would be 2 magnaflow cats with 2 o2 sensors, then mufflers, then out. You need some back pressure further up to get the motor to breathe peoperly.

[OUMike]

According to a local muffler shop working on anything from cat up is against the law (unless replacing of course.) This would make true duals against the law on anything that doesn't already have it.

[Roostman]

I had a friend do it to his 89 Silv. with a Borla muffler, and it sounded like Jeff Gordon's rig. It was sweet. Im not sure if his mileage suffered or not but it is defineately a Federal offence and will get you into a heep of trouble if you get caught.

[sxmax]

Forgot to add that it is illegal to take cats off. That is why on a truck like the one in question, second cat is necessary for a true dual system.

[99Silver6.0]

Thank god theres no emissions testing in KS. Ive got no cats. I made 9 more horse without them through a stock y-pipe. Man oh man did it get raspy though!

[coop]

Theres no emmissions testing here so nobody would know that it didnt have converters. also, he is not concerned about that. he just wanted to see if removing the converters would affect his engine/truck in a negative way.

 

99Silver5.3,

first of all, you have a beautiful truck. i love GM swb 2WD's. Now for a few questions: Do you have your O2 sensors in your Y pipe? If so, where at. and if not, what did you do with them.

 

-coop

[Ben]

Federal law governing emmissions components and systems. Even if no testing, if caught, fines and even jail time.

 

Plus certified mechanics and shops won't touch it for they too will face license suspension/lose/etc, fines and jail time.

 

Finally, on a 1996 and it's OBDII system, it won't run right without them. Computerized controls knows just enough to be stupid. If something is not right, or missing....it won't know and continue to manage as it.

[coop]

Ben,

Thanks for your reply. When you say it will not run right without them, what exactly will it do? Sorry for all of the questions, I just want to be able to explain it to him.

 

-Coop

[Ben]

....Thanks for your reply.  When you say it will not run right without them, what exactly will it do?  Sorry for all of the questions, I just want to be able to explain it to him....

 

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1996, so OBDII (on board diagnostics II). The computer system that manages and monitors (tells big brother about itself whenever "they" plug in).

 

Has 4 oxygen sensors (O2 sensors). Two in front of the CATs tell the computer system (ECU, engine control unit) what the exhaust mixture is. These two has built in heaters to get them up to temp faster and cost more than non-heater O2's. The two behind the CATs tell the ECU how the CATs are doing.

 

It will run without them, but how well? Will it be too lean? Too rich?

 

What if you get stopped and they "see" no CATs. The cop can then plug in an OBDII scanner and confirm. Hosed if this happens. I don't know your area, but since federal law...."your" cops have to enforce those laws....

[99Silver6.0]

Theres no emmissions testing here so nobody would know that it didnt have converters.  also, he is not concerned about that.  he just wanted to see if removing the converters would affect his engine/truck in a negative way.

 

99Silver5.3,

first of all, you have a beautiful truck.  i love GM swb 2WD's.    Now for a few questions: Do you have your O2 sensors in your Y pipe? If so, where at. and if not, what did you do with them.

 

-coop

 

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Thanks man. I turned off the codes for the rear O2's with Edit and unplugged them. Runs fine...... And no codes thrown! The rear O2's dont do anything anyway. Fronts are the most important. Rears are just there for cat efficiency and cat-over-temp. Pretty much worthless. It'll run fine without them, they do not alter the A/F.

[dougmac]

Yes, it is illegal and my sincere hope is that you do get caught and fined to the full extent of the law.

 

I don’t know why you think it is ok for my family (including my small children) to breath the poison that comes out of your exhaust pipe so that you can have an some measly amount of gain in horse power.

 

Doug

[coop]

Dougmac,

I am sorry if i uspet and/or offended you; that was not my intent. I was simply wondering the effects of removing the catalytic converters.

 

99Silver5.3,

So do you still have the front converters on?

 

-coop

[toyotatech]

Yes, it is illegal and my sincere hope is that you do get caught and fined to the full extent of the law.

 

I don’t know why you think it is ok for my family (including my small children) to breath the poison that comes out of your exhaust pipe so that you can have an some measly amount of gain in horse power.

 

Doug

 

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Lighten up doug.

[facn8me]

Several company's make o2 eliminators for the second o2 sensor. They plug in and send a normal signal to the ecm.