Quote:
Originally Posted by ksa8907
Diesels have low vacuum because they don't have a throttle, they control engine speed with fuel.
I'm going to challenge you on that. The prius uses late intake valve closing which decreases vacuum because it pumps the intake gases back into the manifold, does not increase vacuum.
Hybrids do not need to have high vacuum for idle quality because... hybrids don't idle.
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I see where the confusion lies. I'm not referring to "manifold vacuum". I mean the vacuum that the downward piston creates as the intake valve is opening. Fundamentally every engine, otto and diesel, create low pressure inside the cylinder which causes air to flow into it (disregard turbos for this argument). Diesels don't have a throttle, so a sensor in the plenum would essentially read atmospheric; the same thing happens in an otto engine at wide open throttle. Air still flows at WOT, which means there is still a pressure differential in the cylinders. I hope that's clear(er).