Helping the Environment – Tuning Your Car
The catalytic converter has been with us since 1975 , yet there are many owners and even some technicians, unfortunately, who do not realize the effect that it has on a vehicle's power, fuel efficiency and performance.
When the converter is working properly, it cleans up the harmful and deadly exhaust gases that are emitted by your vehicle's operating motor. This is done to the safe standards acceptable to our various Canadian Ministries of Environment (Federal and Provincial) as well as to the U.S. Environmental Protection Agency (EPA).
When a converter is not working properly, it fails its primary job and contributes to loss of power, poor fuel economy, stalling and rough idling. This failure of the converter, in most cases, is the result of the malfunction of some other system in the engine.
How a Converter Works
Today's converters are made of a honeycomb material coated with platinum and palladium. In the presence of oxygen, these two elements aid in the reduction of hydrocarbons (HC) and carbon monoxide (CO).
The Techncial Stuff
To do the job right, the air/fuel ratio must be 14.7:1 or leaner. If the air/fuel ratio is richer than 14.7, the converter does a poor job of oxidizing the HC and CO. However, this fuel ratio often exceeds 14.7 and at this point, the third element inside the converter - rhodium - comes into play . Rhodium, inside the converter, is used as a reducing catalyst - hence the name catalytic converter. It speeds up the chemical reaction by removing oxygen from the nitrous oxide (NOx), leaving only nitrogen. But for this to occur, the air/fuel ratio must be 14.7 or richer. This really means that the engine air/fuel ratio, whether by carburetor or by fuel injection, is always treading a very fine line between producing the optimum environmental emissions and/or the life expectancy of the catalytic converter.
Life Expectancy
Under normal operating conditions, the converter can last for more than 150, 000 miles or 240,000 kilometres without any problems. However, under some conditions it can go into melt-down in a short time.
This can be caused by a driver pumping the throttle, starting and driving the car under choke conditions or leaving the car warming up in the driveway while going back in for a second cup of coffee. The raw fuel introduced into the converter produces severe heat and a possible resultant melt-down.
The converter does not like contaminations of any kind. Tetraethyl lead (leaded gasoline) is an absolute no-no. If you use some by accident, it's goodbye catalytic converter. Ethylene glycol (antifreeze) from a leaking head gasket is another one to avoid. It can coat the honeycomb innards and produce clogging.
Converter failures are usually a symptom of a problem farther forward in the power process that has been neglected or overlooked.
Service Considerations
For the first five years or 80,000 kilometres (depending upon warranties), the emission system is the responsibility of the manufacturer. Once past that warranty, the owner is on their own.
For some, this could be just about the time when the engine starts to need some critical work to repair rich fuel conditions. Or it could be the time when other problems of raw fuel from poor ignition and excessive oil consumption are about to rear their ugly heads.
Common Failure Problems
Remember, most converter failures happen for a reason. Failure is often an indication of problems with other exhaust components such as an oxygen sensor, air manifolds, exhaust check valve, temperature sensor, fuel injector or lack of routine maintenance. Even spark plug wires should be inspected and replaced if needed. The most common problems with catalytic converters are clogging and melt-down, both of which come from high mileage engine malfunctions that cause exhaust restrictions. Exhaust restrictions are one of the greatest power and economy-robbing factors in engine performance. If you can't get the exhaust gases out, you can't get the power producing gases in.
