Quote:
Originally Posted by christofoo
Very good, hang on, we're starting to converge now.
Which is greater, the increase in fuel consumption or reduced pumping loss? Let's back up and set the problem up to work out the same way you analyzed lean burn. Start by taking the fuel that would have gone to cylinder 1, and distribute that fuel to the other 3 cylinders. Cylinder 1 is cut, now we're consuming the same amount of fuel per cycle with 3 cylinders that we would have consumed with 4.
But, as you pointed out, the fuel per cylinder has gone up, so manifold vacuum must go down to get more oxygen into each cylinder to maintain stoich AFR.
Agreed?
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Right.
However, if we assume that we keep available work per firing cycle constant, we have to increase the available work per firing cylinder to cover the lost available work from the deadbeat cylinder. This requires that the firing cylinders' produced work must increase, which means more fuel being consumed by the firing cylinders in the firing cycle.
We must also cover the deadbeat cylinder's pumping work, which means that we must increase the firing cylinder's produced work that much more. This means even more fuel must be consumed by the firing cylinders.
All these things will lower intake manifold vacuum in order to provide enough oxygen to the firing cylinders, which will in turn lower the pumping work being consumed by all of the cylinders. However, are you really reducing the per-firing-cycle fuel being consumed?