Emissions, Performance, and Annoyances: Silverado Catalytic Convertors

The Silverado’s engines run by burning a mixture of air and fuel. As the fuel burns, harmful byproducts are produced. Prior to the existence of catalytic converters, these harmful gases would be released into the air through the exhaust system. Since the Silverado has been produced, catalytic converters have been in place due to emissions regulations in the United States.

What are the Catalysts: By definition, a catalyst is a substance used to speed up a chemical reaction. The catalysts used in a catalytic converter on a Silverado are a combination of platinum and rhodium. These substances are used to breakdown the harmful gases produced by an engine which are carbon monoxide, nitrogen oxides, and hydrocarbons. As these gases pass through the catalyst, less harmful substances will be produced such as nitrogen gases, carbon dioxide, and water.

The factory catalytic converters can be extremely restrictive to air flow, which hinders the amount of power produced by the engine. Because of this, aftermarket suppliers have produced high flow catalytic converters to help free up some of the lost power.

High Flow Cats vs Standard Cats: High flow catalytic converters work almost the same as standard cats do. The exhaust is pushed through a catalyst where the necessary chemical reactions can occur. The difference lies in the layout of catalysts. Honeycomb designs with wider passages are used to help the air flow through at a high rate. This higher rate of flow does only increase peak power output on a minimal level but the power band will see an increase across the entire RPM range.

During the build-up of your Silverado you will begin to question whether you should upgrade to high flow catalytic converters or to delete them entirely. Both will result in an increase in power, but you will need to balance the need for power with the requirements of the build.

When to Install a High-Flow Cat: High flow catalytic converters can be used to help increase power in several builds. The most important feature of a high flow cat is in most cases, they will meet the requirements of state emissions regulations. This is a great upgrade to make for any Silverado owner who intends on keeping their truck as a street driven vehicle.

When to Delete Your Cat: For the best results in terms of increased power, you will want to delete the catalytic converter all together. Even high flow cats cannot compete with power gains seen from the complete removal of the units. The drawback to this modification is once it’s done, the truck will no longer be considered street legal. For off-road and racing applications, deleting the cats is an absolute must.

Silverados will have downstream oxygen sensors in place on the exhaust system right behind the converters to get a live reading of their condition. Deleting the cats will cause these sensors to pick up a bad reading which will throw a check engine light. There are oxygen sensors designed to work with this modification to stop the check engine light and can be purchased for a very small fee. There is an alternative option of stacking sparkplug non-foulers together and drilling them to accept the oxygen sensor. Both methods will result in tricking the computer into believing the reading picked up is due to an intact catalytic converter.

Catalytic converters are but one restrictive portion of the factory exhaust system. High flow cats and cat deletes should not be used as the sole upgrade you make to your truck’s exhaust. Instead, they should be used to complicate other mods focused on increasing the flow of exhaust. When done as so, they will help the vehicle’s maximum potential.

Headers: Right out of the gate the exhaust will have issues with flow. Factory exhaust manifolds do not flow well. The ports are limiting in design and are designed just well enough for the exhaust to escape the cylinder head. Exhaust headers are designed to give each individual port a particular rate of flow it will need for air to flow more freely. They also have greater scavenging effects to help ensure even more air can be pulled through by natural pressures.

Custom Exhaust: Even with exhaust headers and high flow cats or a cat delete in place, the exhaust will have to face the remainder of the exhaust system. The factory routing of the exhaust, pipe diameter and the OE mufflers all pose their own individual issues in how the air passes through. Complete aftermarket exhaust systems are designed to improve all of these areas. For the best results, a combination of the three discussed modifications must be made as they will work to bring up peak power and spread the most power across the power band of the engine.