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If you have a social conscience (or just dont like paying huge fines and having your car impounded), then consider catalytic converters a necessity. Modern catalytic converters arent nearly as restrictive as older units and can help prevent dangerous pollutants from entering the air and groundwater.

The Law

The main reason why catalytic converters are necessary is that the law says so. Catalytic converters were originally a voluntary measure but became required equipment for all cars sold in America in mid-1986.

Carbon Monoxide

One of the main jobs of a catalytic converter is to convert the dangerous pollutant carbon monoxide into harmless carbon dioxide, which it does with nearly 99 percent efficiency.

Nitrogen Oxide

Considered a volatile organic compound (VOC), nitrogen oxide reacts with sunlight to form smog. Catalytic converters break this toxic chemical down into its component oxygen and nitrogen molecules, making for cleaner skies and longer lives.

Unburned Fuel

No engine burns all of the fuel that it ingests. Catalytic converters burn what little unburned gas the engine hasnt consumed to keep it from polluting groundwater upon exhalation.

Computer Issues

Removing a catalytic converter without installing a simulation sensor will cause a cars computer to malfunction, which will drop engine power by changing fuel and spark parameters until the catalytic converter is replaced.

Automotive cooling systems are complex beasts, not so much in form as in function. The cooling system is more than just a water hose to keep the engine cool, its a support system used to keep all of that hot, fast-moving metal working the way it should be.

Function and Design

A thermostat sits in the base of the hose that moves coolant from the engine to the radiator, and serves to restrict flow to the radiator when the engine is cold. Most thermostats use a wax-pellet design. Below a given temperature, the wax pellet remains a solid, keeping the thermostat valve shut and causing the coolant to recirculate inside of the engine instead of going to the radiator. Above its set temperature, the wax pellet melts and allows the valve to open.

Purpose

You dont technically "need" a thermostat; the engine will continue to run without it. A thermostats primary job is to get the engine up to temperature as quickly as possible and then limit flow to keep it at that temperature. Running without a thermostat will allow coolant to constantly circulate through the radiator, which can cause the engine to run far cooler than it should. While this might seem like a good thing at first glance, bear in mind that most engines are engineered to run best when theyre fairly hot.