So Fix it

Catalytic converters use exhaust heat trapped in a matrix of ceramic plate and precious metals to change exhaust gases chemical composition to a more benign form. Quick-moving gases might sometimes lack the opportunity to catalyze fully, which may require two or more converters.

Converter Function

Converters contain a honeycomb-like ceramic matrix with thousands of tiny passages. Exhaust flows through these passages, combining with the platinum, rhodium, palladium and cesium on the passage walls to add or subtract nitrogen or oxygen atoms. This gain or loss converts the toxic molecules in the exhaust into more benign forms.

Emissions Requirements

Different countries and unions have different emissions requirements and require different catalytic converters. The European Union disallows the use of nickel in converters but permits copper (which the United States does not). Most large car manufacturers offer several variations on the same chassis to market all over the world. Using more than one converter allows the manufacturer to meet local emissions standards while using the same basic chassis worldwide.

Modularity

Not all car manufacturers produce their own catalytic converters; many converters are outsourced from specialty catalytic converter manufacturers. Because most cars come with a number of different engine options, manufacturers may need to mix and match different converters to meet emissions requirements for a particular engine-chassis combination.

The catalytic converter is part of a vehicles exhaust system and serves to reduce the amount of toxic gases emitted into the atmosphere. These surprisingly simple components have served to dramatically reduce the amount of vehicle emissions produced over the past few decades. Today, they are installed on all factory-produced vehicles sold in the United States.

History

The Engelhard Corporation invented the first production-ready catalytic converter in 1973. A couple years later, the Environmental Protection Agency introduced more stringent regulations relating to vehicle emissions. Confronted with these new requirements, auto manufacturers quickly embraced the new earth-friendly product. The 1975 vehicle model year was the first time that the catalytic converter came pre-installed on new cars.

Effects

The first catalytic converters on the road were known as 2-way catalytic converters. Cars with such technology are capable of converting hazardous carbon monoxide to harmless carbon dioxide. They also break down toxic hydrocarbons into carbon dioxide and water. In 1981, 3-way catalytic converters became commonplace. Cars with this newer technology are also capable of reducing nitrogen oxides to regular nitrogen and oxygen.

Function

The catalytic converter converts toxic gases to harmless gases via a platinum-iridium catalyst. As the hydrocarbons and carbon monoxide pass through this catalyst, the gases are oxidized. This causes them to break down into less toxic elements. Nitrogen oxides require a separate process, known as reduction, to eliminate toxicity.

Considerations

The catalytic converter is typically situated below the front passenger seat, between the engine and the rear exhaust. In order to function properly, the combustion chamber must be fed the correct ratio of gasoline to oxygen. If too much oxygen or gasoline is introduced, excessive hydrocarbons and other toxic gases will be produced. These extra particles make it hard for the catalytic converter to keep up with the inefficiency of the engine. To eliminate such a scenario, most modern-day vehicles feature fuel injection and oxygen sensors to monitor the oxygen-to-gas ratio entering the combustion chamber.

Potential

Though catalytic converters have been integral in reducing vehicle emissions, there is still more that can be done. The biggest downside to catalytic converters is that they require a great deal of heat to function properly. This heat is generated by the engine, but it takes several minutes after you turn your car on before the catalytic converter becomes effective. Currently, engineers are tinkering with ways to speed up the heating process so that vehicle emissions are cleaned by the catalytic converter during these first minutes of vehicle operation.

The catalytic converters in your Lexus LS400 are three-way converters that lower exhaust emissions through a chemical reaction between the exhaust gas and the substrate in the converter. This type of converter features the reduction capabilities of a reduction converter to lower oxides of nitrogen (NOx) and the oxidation capabilities of an oxidation converter to lower carbon monoxide (CO), carbon dioxide (CO2) and unburned hydrocarbons. Replacement catalytic converters in the Lexus LS400 come installed in an exhaust pipe assembly making replacement easier.

Instructions

1

Apply the parking brake and set wheel chocks behind the rear wheels. Raise and support the front of the Lexus using a floor jack and jack stands positioned under the front sub-frame. Lower the car onto the stands slowly so that the weight of the car is supported evenly by the jack stands. Remove the floor jack.

2

Allow the exhaust system to cool completely. The catalytic converters on the LS400 operate at a high temperature (over 600 degrees Fahrenheit) and can cause severe burns if not allowed to cool sufficiently prior to working on the system.

3

Spray the attaching bolts on the converter with a liberal coating of penetrating oil and allow it to sit for a few minutes. Remove the two rear mounting bolts that attach each of the converters to the exhaust system using a 13mm socket and ratchet to turn the bolt while holding the 15mm nut with a wrench. Pry the exhaust system back away from the converter and pull the exhaust downward.

4

Remove the three 13mm nuts that attach the converter to the exhaust manifold and pull the converter off the manifold studs. Use a new exhaust gasket between the converter and manifold. Bolt in the new converter, leaving the nuts loose so the converter can be moved slightly while lining up the rest of the exhaust system.

5

Raise the exhaust system and pry it back until it can be slipped onto the converter. Place a new gasket between the converters and the exhaust system. Install and tighten all of the nuts and bolts securely.