One of the important tables for fuel or AFR control is the “lambda for component protection”, which is a function of the EGT parameter. In this article, we are going to see how the EGT table works in ECU file.

🚩What is The EGT Parameter?

One of the most important factors in controlling the combustion chamber temperature, which significantly impacts the life of engine parts and pollution, is the AFR. ECU manufacturers always keep the combustion chamber temperature in the permissible range for a series of particular conditions. This combustion chamber temperature can be related to Exhaust gas temperature.

💬What is The EGT Table?

At engine calibration, a table is defined in the ECU as a mathematical model for exhaust gas temperature (EGT). The EGT table helps the ECU understand EGT through this model. It can calculate the EGT and control the fuel mixture by referencing other tables. As you can see in the EGT table below, the vertical axis is engine rpm and the horizontal axis percentage of air or cylinder air filling, and the output of this table is exhaust gas temperature mathematical modeling that we explained.

EGT table map
a sample of EGT table in Bosch ECUs


For example, if the critical exhaust gas temperature is defined as 900°C, ECU will use this table to manage AFR as long as the temperature is below this value. ECU must enrich the fuel to lower the combustion chamber temperature if the temperature exceeds the allowable limit.

💬Lambda For Component Protection:

Lambda for component protection refers to the air-fuel ratio to protect components such as catalysts, turbochargers, smoke manifolds, etc. The axes of this table are based typically on the engine revolution and the percentage of intake air to the cylinder. Here, the vertical axis is the percentage of intake air to the cylinder, and the horizontal axis is the engine revolution. The numbers in the table are lambda for component protection. In some ECUs the vertical axis is engine speed, and the horizontal axis is air filling but in general, there is no difference between them.

Lambda for component protection bosch ecu
a sample of “Lambda for component protection” table in Bosch ECUs

In most engines, manufacturers choose to make the air-fuel ratio rich to reduce engine part temperatures and prevent damage due to high temperatures. When the numbers are less than 1.00, it means the mixture is richer than the stoichiometric ratio, resulting in a cooler combustion. By allowing more fuel to reach the cylinder, any unburned fuel vaporizes at the cylinder walls, cooling them down and reducing the exhaust emission temperature. The enrichment only activates if the modeled exhaust gas temperature or EGT exceeds the applicable threshold or limit.

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