Valves. 4 valves per cylinder, 16 valves, 8
valves???
What's all this about then!!!
Engines make power by burning fuel, and this is limited by the amount of
air or rather oxygen that can be drawn into each cylinder. Some
engines have a single inlet valve and a single exhaust valve. This
would be a 2 valve per cylinder engine. So your average 4 cylinder
car would have 8 valves.
Some cars are "16v" or 16 valves! The reason for this is that 4 smaller valves have lots of advantages over a pair of bigger ones! The main one as far as we are concerned is that a 16valve engine or rather a 4 valve per cylinder engine flows more air and makes more power than a 2 valve per cylinder one can.
The reasons that using four small valves is a better solution than two bigger ones is:
-
The valves can have more total area so can flow more gas when fully open.
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Several small valves have a larger seat area than one big one! This means greater flow at times when the valve is only slightly opened.
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Each valve is lighter, so can be opened faster and closed faster, resulting in more flow.
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Extra seat "length" means better heat transfer so narrower seats can be used giving better low lift flow.