Food for thought...
I believe there is one other reason why cylinder deactivation is required in addition to just turning the fuel injectors off. Yes, there is a pumping loss effect with cylinder deactivation. Another big effect (from Honda’s emission point of view) is that they don’t want any extra air (oxygen) going through the common catalytic converter because it would then behave like a “lean burn” system and NOx conversion would drop to zero. NOx does not convert within a catalytic converter in the presence of high oxygen levels due to chemistry.
In a nutshell, Honda could never meet emission regulations for NOx in “fuel economy” mode if the rear cylinders pumped air through the common catalyst shared by front and rear cylinder banks.
I believe there is one other reason why cylinder deactivation is required in addition to just turning the fuel injectors off. Yes, there is a pumping loss effect with cylinder deactivation. Another big effect (from Honda’s emission point of view) is that they don’t want any extra air (oxygen) going through the common catalytic converter because it would then behave like a “lean burn” system and NOx conversion would drop to zero. NOx does not convert within a catalytic converter in the presence of high oxygen levels due to chemistry.
In a nutshell, Honda could never meet emission regulations for NOx in “fuel economy” mode if the rear cylinders pumped air through the common catalyst shared by front and rear cylinder banks.