Emissions

There are four exhaust gases that get released from cars. Carbon monoxide, carbon dioxide, oxides of nitrogen and hydro carbons. These are harmful to people and to the environment so in order to bring down these gases, vehicles are equipped with "catalytic converters" which takes those harmful gases and transfers it to less harmful gases like carbon dioxide and steam(H20). Another way vehicles lessen the amount of harmful gases is by EGR (Exhaust Gas Recirculation). This recirculates a portion of exhaust and runs it back to the combustion chamber. This also gives a cooler, more complete burn of fuel.

Coolant Temperature Sensor & Air Temperature Sensor

To test the coolant temperature sensor, I had to put it in a bowl of water on a stove and measure its resistance as the temperature of the water goes up. If there was no continuity then that meant that the sensor is not working. The coolant temperature sensor senses engine temperature. If temp. is too high, ECU tells injectors to slow down flow. If temp. is too low. injectors speed up. Air temperature sensor is similar. To test this one, I had to heat it up with a heat gun and record its continuity as the temperature rises.Air gets denser as its temperature increases so cold air would mean more fuel needed to be injected.

O2 Sensor & Diesel Injectors

We spent some time making an O2 sensor from scratch. And then tested it on a voltage regulator tester. The LED lights flashed from green to yellow to red. Green indicating that there is little voltage in the sensor therefore, detecting a lean mix. Yellow is in the middle so this is where we want the indicator to stay. And red means there is alot of voltage, meaning the mix would be too rich. Also tested some diesel injectors. Testing their atomisation and comparing them to the manufacturer specifications. If atomisation was too high, this could damage injectors because pressure would be too much. If atomisation was too low, this could mean not enough fuel being injected resulting in low engine power.

Air Flow Sensor and TPS.

The air flow sensor takes in incoming air and measures how much is going into the engine. The flap is connected to the ECU and the movement of the flap determines how much air is going in. If there is little flap movement then the ECU will know that not much air is coming in so it will send in little fuel to match. If the flap was fully open then the ECU would send in more fuel because it reads that there is alot of air coming through. The air then goes through to the butterfly. The TPS (throttle position sensor) is connected to the butterfly. It reads what position the throttle is in and adjusts the butterfly to open up (amount opened depends on throttle position) to let air in. If the throttle is pushed down a little, the butterfly will open up a little, letting a little amount of air through. The TPS is connected to the MAP (manifold absolute pressure sensor). This measures pressure inside intake manifold. When the throttle is wide open, vacuum from the MAP drops. The engine sucks in more air which requires more fuel to keep the air/fuel ratio balanced. If throttle is near closed, less power is needed from the engine causing vacuum to increase. MAP senses this and ECU responds by leaning out the fuel mix.