I'm have a BS in chemistry, so I can explain the catalytic converter. It contains certain metals that break down carbon monoxide and several other compounds due to electron exchanges taking place on the surface of the catalyst. So carbon monoxide is converted to carbon dioxide and aldehydes are broken down as well. The problem with a hole in the converter, other than the airplane sound is that these chemicals which are toxic to humans are being released, and directly underneath you when driving. If idling at a stop light or in a garage, the fumes are coming directly into the cab. Usually a converter will go bad after a while due to sulfur poisoning but the hole is going to cause the same effects of a bad converter. Lower fuel effiicency and high pollutant release. You should probably replace it, but due to the value of the metals in the converter (platinum, palladnium, rhodium.A few others) it will be very costly. Mine usually run at around $700, But I've found ways to clean them myself. Wouldn't recommend it without a chem lab though.
Tuesday, January 6th, 2009 AT 11:29 AM