Answered on Quora: Can intake and exhaust valve overlap be prevented?

Can intake and exhaust valve overlap be prevented?

Daniel Becker, Patent Attorney and Early-stage Engineering (2013-present)

Answered 21h ago

Yes, with variable valve timing, or with timing systems / cams which have very little overlap.

“Overlap” is a designed-in aspect, however. Your syntax makes me wonder whether you are more concerned with a negative aspect of an engine with a lot overlap. Can you tell me more? Maybe you have put a more aggressive camshaft or a freer-flowing intake on an engine and are concerned that you are not getting efficient combustion or have lost some low-rpm driveability?

Decreasing overlap can be valuable for low-rpm torque or mpg, but they can be detrimental to maximizing performance, because power is a function of engine speed and torque, and valve overlap is valuable to faciliating the mass airflow necessary for an engine to supply a cool and oxygenated and well-mixed intake charge at high speeds.

Rather than decreasing overlap, though, there are other ways to decrease blow-through of an excess of a fuel charge. Is that what you want to know more about?

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