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October 20th, 2009 12:49 PM #11
The number of valves doesn't really matter nowadays... most economy cars have at least three-valve or four-valve per cylinder heads... and the valves are sized to maximize flow capacity. You never want less flow capacity, as this makes the car inefficient and makes it difficult for the makers to meet emissions requirements... as it hinders the mixing of air and fuel in the cylinder.
But basically, correct... more air... more fuel... What really matters in the valvetrain is the camshaft, as this determines valve lift. A mild camshaft gives great economy at the expense of power. A high-lift camshaft opens the door wider for more air and more power. This is why Honda and Toyota use variable lift cams... it allows them to use small valve openings at low rpms for more economy, and big openings at high rpms, for more power.
Honda gearing is very short in the low gears, for good performance in the city, and tall in the high gears, for good economy. Toyota uses evenly spaced gears, but their economy is still good (bit better than Honda on some models... the same on others) because their engines have better low-end response.
A square engine gives the most linear response, but most automotive engines are undersquare... with more stroke than bore... which gives better low-end power, which makes for better fuel efficiency in traffic, as you don't need to rev hard to get going.
Ang pagbalik ng comeback...
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October 23rd, 2009 12:46 PM #13
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samin doc sinasabihan kami "mag nilay nilay" - be quiet. Bawal magsaya (common sense) and music or...
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