Quote:
Originally Posted by christofoo
This is all correct.
Now consider that when we go from 4 firing cylinders to 3, changing nothing else, the 3 are not consuming enough fuel to produce as much work as 4.
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So, we have a set amount of produced work, now per firing cycle instead of per cylinder. We have a set amount of pumping work being consumed per firing cycle, instead of per cylinder. We produce a set amount of available work per firing cycle, instead of per cylinder.
We shut off one cylinder via DCD. The remaining cylinders are still producing work. You pointed out that the remaining cylinders are producing less work per firing cycle, than before.
So, we need to increase the amount of fuel to the remaining cylinders, so they can provide the amount of available work as before, while also covering the slack of the deadbeat cylinder caused by DCD.
Hm... The other cylinders are already operating at stoich, right? So we must also increase the amount of oxygen going to the running cylinders! Okay, so we lowered intake manifold vacuum by a bit. Good deal! We just lowered the pumping work for all of the cylinders, right?
Waitaminute... We just increased the amount of fuel to the remaining cylinders. We did this to cover the deadbeat cylinder, which is still consuming pumping work. The pumping work per cylinder may be less than before, since we just lowered intake manifold vacuum, but we also increased the work produced by the remaining working cylinders.
Right?