Exhaust Temperature Sensor │ Car Exhaust Temperature Sensor


What is Exhaust Gas Temperature Sensor?

Why does measuring or Monitoring Exhaust Gas Temperature important?


Whenever we decided to buy a Car, Truck, or bike. We want things like Mileage, Performance, Power, Comfort, and safety in our Car, Truck, or even bike. But have you ever wondered how do automakers able to do these things in our vehicle? Whenever we want to add extra horsepower into the engine we have to face so many challenges like adding extra cooling systems, proper exhaust, emission controller. Every five or ten years thing related to software and hardware of the automobile sector change due to demand or policy. To satisfy customer demand and needs automakers need to update their technique of making engine, parts, sensor, and other subsystems.Exhaust Gas Temperature sensor is a very important and critical part of the engine management unit. EGT tells Electronic Control Unit (ECU) about the temperature of Exhaust gas coming out from the engine going into DOC, DPF, SCR.


What is Exhaust Gas?


A mixture of Air+Fuel burns inside the engine cylinder under high pressure and temperature. Combustion of mixture creates high temperature & high-pressure gases which expand and converted into power or torque. But about 40% of energy from gases converted into useful work and rest of 70% of energy release through engine wall, exhaust gas.
Exhaust gas is a mixture of burnt Hydrocarbon, Carbon Dioxide, Sulfur, Carbon Monoxide, Nitrogen oxide.
Carbon Dioxide,Sulfur, Nitrogen oxide, Carbon monoxide is very harmful to the environment and human being.
To restrict these gases going into environment automobile manufacturers make a system called Emission Control.
Emission control is a very complex arrangement of DOC, DPF, SCR. Each sub-component or system works under specific temperatures. To monitor temperature at each component need a temperature sensor.

What is Exhaust Temperature Sensor?




Automobile engine becoming more and more complicated and environment friendly but at same time even more powerful. This is achieve by way so call engine downsizing,mean reducing engine weight size. At same time using advance sensor turbo/supercharger to increase mechanical power and torque. 
As the name suggests Exhaust Gas Temperature sensor measures the temperature of exhaust gases. This information or collected data shared via wiring to an engine control unit or ECU. Based on information ECU will decide to maintain engine performance & efficiency at maximum level. 


Exhaust Gas Temperature Sensor Section View


How does Exhaust Temperature Sensor Works?


Exhaust gas temperature sensor work on the principle that change in exhaust temperature changes resistance value of the sensor. This change in resistance may be high or low. There are two types of sensors available for this type of measurement called NTC(negative temperature coefficient) or PTC ( positive temperature coefficient).
NTC sensing elements resistance increases if the temperature of exhaust gases decreases. 
In PTC sensor sensing elements resistance increases with temperature increases of exhaust gases.
This will result in the voltage output of the sensor.

Importance of Exhaust Gas Temperature Sensor


Petrol Engines 

In Petrol engines, an exhaust gas temperature sensor located after/before Catalytic convector or turbocharger. The main role of EGT here to protect components like a turbocharger and Catalytic convector from overheating. 
In the case of Turbocharger:- If the temperature of exhaust gases reaches excessive level, the engine control unit lower down boost pressure which results in lowering the temperature of a turbocharger. Without EGT, bearing and turbo assembly get affected badly.
There is a temperature difference of 100℃ -200℃ before/after the turbocharger. This heat energy consumed in compression of air.
In Case of Catalytic convector: EGT sends a signal to ECU, based on signal ECU allows injectors to inject a small amount of fuel into Catalytic convector. This injection of fuel decreases the temperature of the catalytic converter from 850℃ to 700℃. 

Diesel Engine


Diesel engines are operating on higher temperatures as compared to petrol engine to achieve higher thermal efficiency.
Here Exhaust gas temperature sensor installs not to protect components from overheating, but to ensure DOC and DFC are reaches to regeneration level.
Exhaust gas temperature sensor used to monitor the temperature of Diesel particulate filter (DPF) and Diesel Oxidation Catalyst (DOC). EGT ensures that the temperature of PDF and DOC reach at oxidation level so that the regeneration process will begone. This process helps to reduce the pollution level.

Additional Application of Exhaust Gas Temperature Sensor

 

Exhaust gas temperature sensors are used in nitrogen oxide (NOx) reduction assembly. Here the main purpose of temperature monitoring is to maintain the minimum temperature required for the operation of Catalytic convector and to protect these against overheating. 

The modern exhaust temperature sensor has to measure range from -40 to +900˚C
Nowadays Exhaust Gas re-circulation unit is now equipped with an exhaust temperature sensor. The measurement from EGT help in diagnosis (OBD-II) for the EGR system.
 A sensor installed in the EGR system based on the same working principle as other temperature sensor but with a measuring range of 500℃


Conclusion



The automobile industry needs to follow rules and regulations of the government,at the same time satisfying customer needs of high mileage, high engine power, better safety standards. This is not too easy but as technology change automakers come with new sensors and systems to meet these demands. EGT is also one of them it protects critical components, saves the environment by sharing exact information of exhaust gas temperature to ECU.


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