I saw this advert in the newspaper selling the new polo.
They listed the engines:
1.2L 55PS 6V
1.2L 65PS 12V
1.4L 75PS 16V
1.4L FSI 86PS 16V
1.4L 100PS 16V
1.9L SDI 64PS 8V
1.4L TDI 75PS 6V
1.9L TDI 100PS 8V
Is this right?
Not knowing much about valves and cylinders, I just thought it was a bit odd as I thought they were either 12v or 16v?
James.
How many valves?
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polo2k
- Bling Bling Diamond Member
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well the way that valves and cylinders work is:
each cylinder in a 4 stroke engine requires at least 2 valves per cylinder (1 for inlet and one for exaust)
howexer if you use 2 smaller valves (or more) in place of 1 valve then the surface area of the valve heads combined is greater than the single valve* and thus the valce combination can flow more gas
in some instances there arn`t an even number ov valves per cylinder as in the 1.8 turbo which uses 3 inlet valves and one exaust so that as the air is being forced in there is lots of room but on the exaust there is 2 bigger valves but this flows about the same as the 3 smaller ones because the turbo creates a vacuum which draws the gas out.
this information alows us to calculate the number of total valves if we know how many cylinders there are and how many valves per cylinder i.e.
the 1.2 6V is a 3 cylinder engine with 2 valves per cylinder so 3x2=6
the 1.4 16V is a 4 cylinder with 2 inlet valves and 2 exaust valves percylinder (giving a total of 4 per cylinder) so 4x4=16
the 1.8 turbo found in golfs is a 4 cylinder with 5 valves per cylinder so 4x5=20 valves total
however some engines dont use valves at all such as rotary engines and 2 stroke engines which use some sort of rotating/sliding object to cover/uncover a hole in the wall of the combustion chamber
yet again there is another exeption, the 2 stroke diesel which is not currently used in cars which is a cross breed between a 2 stroke with a hole in the cylinderwall which is blocked and uncovered by the piston for the inlet but the exaust uses valves as in a 4-stroke. this engine must however use a form of forced induction, however i shall not go into deatail here as it is irrelevent
*imagine drawing a circle that you can fit 2 2P pieces in then you remove one 2p piece and replace it with 2 1p pieces then there is less uncovered space in the circle so therfore more area is used
i hope all this babble makes sence but its 3.15am basically it depends on the number of valves per cyinder multiplied by the number of cylinders
each cylinder in a 4 stroke engine requires at least 2 valves per cylinder (1 for inlet and one for exaust)
howexer if you use 2 smaller valves (or more) in place of 1 valve then the surface area of the valve heads combined is greater than the single valve* and thus the valce combination can flow more gas
in some instances there arn`t an even number ov valves per cylinder as in the 1.8 turbo which uses 3 inlet valves and one exaust so that as the air is being forced in there is lots of room but on the exaust there is 2 bigger valves but this flows about the same as the 3 smaller ones because the turbo creates a vacuum which draws the gas out.
this information alows us to calculate the number of total valves if we know how many cylinders there are and how many valves per cylinder i.e.
the 1.2 6V is a 3 cylinder engine with 2 valves per cylinder so 3x2=6
the 1.4 16V is a 4 cylinder with 2 inlet valves and 2 exaust valves percylinder (giving a total of 4 per cylinder) so 4x4=16
the 1.8 turbo found in golfs is a 4 cylinder with 5 valves per cylinder so 4x5=20 valves total
however some engines dont use valves at all such as rotary engines and 2 stroke engines which use some sort of rotating/sliding object to cover/uncover a hole in the wall of the combustion chamber
yet again there is another exeption, the 2 stroke diesel which is not currently used in cars which is a cross breed between a 2 stroke with a hole in the cylinderwall which is blocked and uncovered by the piston for the inlet but the exaust uses valves as in a 4-stroke. this engine must however use a form of forced induction, however i shall not go into deatail here as it is irrelevent
*imagine drawing a circle that you can fit 2 2P pieces in then you remove one 2p piece and replace it with 2 1p pieces then there is less uncovered space in the circle so therfore more area is used
i hope all this babble makes sence but its 3.15am basically it depends on the number of valves per cyinder multiplied by the number of cylinders
