Hollowed Cats sound bad. Aside from that, if your car has any O2 sensors downstream from the Cat (nearly all late model cars do have downstream O2's) the computer will go insane and the mileage will fall like a rock. The Check engine light will also be on. I'm only scratching the surface of the issues here.
As others point out, it is a bad idea to do that to a modern car (besides being a federal offense with a presumptive fine of $10,000). Most of the time the car will run worse, sometimes much worse, without the catalytic converters being fully operational. You don't mention make, model, or year, but some cars go into a mild "limp home" mode and greatly restrict power.
Many new cars will not run right with the cat not working. They will detect too much NOx and unburned HC in the exhaust. The car's engine controller will try to lean out the mixture to reduce the HC and try fool with the timing to reduce the NOx. At the same time. The conflict will make your car run erraticaly and will decrease your MPG.
The only purpose in the old days to do this was to be able to use leaded gas as it was cheaper. But with leaded gas not being available for over 20 years now, there is no point. And you are also committing an anti-social act by making the air dirtier for all of us, including yourself.
You know your check engine light will trigger from this.. All for what 5-10 HP maybe? Also you might only get to use it for a year or two at least till your next smog test. Also be warned it is a 10K fine for the owner of the car, a 10k fine for the person that does it and a 10K fine for the owner of the shop..So if you do it yourself and get caught thats 30K.. You could just weld in a cast iron y-pipe with a butterfly valve to dump the exhaust before it even touches the cat. Yeah the CEL will trigger when its opened but goes away after its closed..
I have a 88 Mustang Gt. The guy I bought it from had hollowed out the convertors and the car ran great. It passed 2 e checks before i changed the exhaust (because it was rotting). I found out the cats were gutted when I took cut the old exhaust off. It depends on your situation. Regular mechanics will tell you anything other than factory parts are bad. Ive had them tell me that aftermarket catback exhausts, headers,freeflow airfilters will ALL make your car run like crap. Somethings just arent true.
I believe you should not be operating a motor vehicle if that is your thought process. Specifically if it is still under warranty. OMG I forgot how fun it was to read Yahoo questions. Plus it doesn't matter if the mechanics don't notice. The computer will know and put a little check engine light on.
Sure, because people who work in muffler shops are idiots and won't know the converter has been gutted when they pick it up off the floor. Your warranty won't cover this, and you could be subject to a fine. It's illegal to tamper with an emission control device.
Hhmm. First, pal around with the mechanic. They don't like to waste time but they like to pal around briefly. Then, direct him to add a $5 tip to the bill. Since you are replacing it he should have no problem with it. It is only a question of whether he will report it to the company. Maybe the insides got blowed out. Play dumb.
Hollow out the cat and the computer will have a fit. Multiple codes will pop up in your computer. What purpose would "hollowing" it out serve? Why would you think hollowing it out would improve anything?
I want to hollow out the cats but I have a warranty on my car, if something went wrong with the car after hollowing out the cats couldn't I replace them with new ones before sending a warranty claim and without it being noticed the original ones were hollowed out?
The check engine light will illuminate and the car will not pass state inspection.
Your car will stink if you do that, and it will cause a lot of ozone depleting pollution, for what? More noise? One or two more horsepower? Are you stupid?
Tampering with a catalytic converter is illegal.
You cannot pass a smog inspection and therefore cannot register your car.
Silly boy.
