How Do Cars Control Emissions?
You’ve probably heard a lot about emissions and why they need to be controlled. But have you ever wondered what they are or how cars keep them under control?
The emissions themselves are a combination of burned and unburned substances like hydrocarbons, carbon monoxide, nitrogen oxides, and sulfur oxides that can come from the combustion chamber and the crankcase. In older cars, the emissions can also include gasoline fumes from carburetors. These emissions are controlled by a combination of mechanical and technological systems.
Combustion Emission Controls
A big part of the issues with emissions is the fuel that isn’t burned, so a key system returns this unburned fuel to the combustion chambers. This is done with a positive crankcase ventilation valve, or PCV valve, that combines leaked combustion gases with air, then pumps them back for combustion.
Emissions can also be limited by controlling the combustion itself. That’s where electronic fuel injectors come in. As of the mid-1990s, these completely replaced the old carburetor systems. The fuel injector systems create a much more precise fuel-air mixture to cut down on fumes and get more efficient burns.
Exhaust Emission Controls
Excess heat in the combustion chamber produces more nitrogen oxides. To keep that down, an exhaust gas recirculation system (EGR system) takes a portion of the exhaust and routes it back to the combustion chambers. This lowers the temperature, helping reduce the amount of nitrogen oxides.
Past the EGR system, the exhaust passes through a catalytic convertor, which has metal that converts the hydrocarbons, carbon monoxide, and nitrogen dioxide into water, carbon dioxide, and nitrogen.
Electronic Emission Controls
They key to truly controlling emissions is precision, and that’s why the most important component of a modern emissions control system is the electronic control unit (ECU) of the car. This computer monitors the car’s performance, then adjusts systems like the fuel injector to make sure the car is running as efficiently as possible. The ECU also has the built-in capability to monitor the emissions, allowing it to adjust to run as cleanly as possible.
Controlling Emissions vs. Providing Power
The place where things get sticky for manufacturers is trying to balance power with efficiency. More efficient engines will use the least amount of fuel to move the car, generating less emissions, but also providing less acceleration or power. More power means more combustion and more emissions, especially when you’re asking for a lot of power in a short period of time for high acceleration.
Emission controls have come a long way since the smoggy 1970s when modern emissions standards were first introduced, and every year more advancements are made. And with the rise of hybrids and electric cars, the amount of average emissions per vehicle will just keep getting lower.