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Boost Control when the exhaust temperatures is too high

Understanding AFR

Discussion and questions related to the course Understand AFR


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Hello mates,

I would like to ask how an overly retarted ignition (as mentioned in the Ignition compensation section) can cause a high exhaust temperatures and how this can also affect boost control.

Many thanks in advance.

As you retard the ignition, the combustion starts occurring later, and more of the heat goes out the exhaust valve instead of being converted into force on the piston. That raises the exhaust temperature.

At low rpm in some very specific situations (anti lag etc), retarding the spark could actually increase the boost. The hotter exhaust provides more energy to the turbo. However if you have a turbo that does not have much problem spooling up it's not going to help. At high rpm retarding the spark is more about avoiding knock.

... and less of the heat released by cumbustion of the fuel is absorbed by the piston, cylinders and head and so there is more to be absorbed by the turbocharger turbine and housing.

Well said and explained thank you very much !

are we having any courses about antilag ?