Judy Cooper
Ansys Employee

Hi Elisa:

This should be possible if the change you make has a significant impact on temperature

The HCCI engine model has options for the heat transfer models (under the "Heat Transfer Parameters" tab): 
As a simple test, I would try the Heat Loss Heat Transfer Option first, because you can specify how much energy is removed from the system:
For the adiabatic condition, simply set the "Heat Loss" to 0.0:
Then, try a non-zero heat loss to evaluate the difference.
Heat loss affects the engine gas temperature, and most common combustion reaction rates are temperature-dependent; so changing the heat loss rate (heat transfer parameters) will have an impact  on the reaction rates.   (This effect will be positive or negative depending on the fuel species and conditions.)
I hope this helps.
Best Regards,