Quote:
Originally Posted by christofoo
Fuel input has not changed since we started DCD. Produced work has not changed. The number of cylinders experiencing pumping loss has not changed. But manifold pressure has gone up, manifold vacuum has gone down, pumping loss has gone down.
And this means available work has gone up.
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Sorry, no.
Available work has not changed, but produced work has gone up to cover the deadbeat cylinder.
It's really very simple - with DCD, you're running an internal combustion engine at stoich (or rich due to the engine computer going into limp-in mode), with what amounts to an air compressor that gets its air supply from the intake manifold, which then discharges into the exhaust stream.
Yah, pumping work will go down as compared to a normally operating otherwise identical engine, but the DCD engine will still consume more fuel than the normally operating one, because you just added an extra load to it, all other things being equal. That load is the pumping work associated with the deadbeat cylinder.