4 Valves per cylinder?

Question

Just wanted to know what the significance of the number of valves is?

I know that theres valves for intake and exhaust if i'm correct.

if there is four i'm guessing its 1 for air and 1 for fuel if its fuel injected. and 2 for exhaust?

are there bikes with 3 valves or more than 4 valves and why?

and a basic carburated 2 stroke just has an intake from the carb side and then an exhaust.

please give me more info and let me know if i'm correct or not.

Answer 1

It's two intake valves and two exhaust valves. The intake valves both have the same fuel/air mix going through them. It just gives the engine a bigger port to send the mixture through. Thus sending more fuel/air mix into the engine for more power. It's easier to fit four smaller valves than it is to fit two big valves into the combustion chamber. And the two exhaust valves give a bigger port to get the burned gas out of the combustion chamber faster.

Answer 2

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RE:

4 Valves per cylinder?

Just wanted to know what the significance of the number of valves is?



I know that theres valves for intake and exhaust if i'm correct.



if there is four i'm guessing its 1 for air and 1 for fuel if its fuel injected. and 2 for exhaust?



are there bikes with 3 valves or more than 4...

Answer 3

As goobersmooch says, your guess regarding 4 valves is wrong. On a 4-valve engine (i.e. that means 4 valves per cyclinder) there are two exhaust and two inlet valves.



I can't remember offhand if there are bikes with 3 valves, but there are definitely cars with 3 valves. They are usually one inlet, two exhaust, because the exhaust valves get hotter (having to deal with hot burned gases) and two valves give a better surface-to-volume ratio, thus aiding with keeping them cool.



I'm fairly sure there are bikes with 5 valves per cylinder, but I'm danmed if I can remember what they are. Why? Same principle applies - more valves in a given space means a better area for the gases/vapours to flow over = more efficiency. But eventually the ol' cost/benefit ratio catches up. It's harder to make a valve train to open 5 valves than it is to make one to open 4,3, or 2.



All engines have their intakes on the carburettor side, whether 2-stroke or 4. Or, more acurately, their carbs are on the intake side. 2-stroke valves, if they have any, are completely different to 4-stroke, and they are on the intake side only. A 2-stroke engine doesn't necessarily need to have valves.

Answer 4

4 valves 2 intake 2 exhaust some single cylinder bikes have 5 2 intake 3 exhaust

a 2 stroke engine has 0 valves they have an intake and exhaust port cut into the piston

Answer 5

3 valves: 2 intake, 1 exhaust (Honda CM400/450, for example)

4 valves: 2 intake, 2 exhaust (very common)

5 valves: 3 intake, 2 exhaust (some Yamaha sport-bikes)

8 valves; 4 intake, 4 exhaust (Honda NR bikes only)



Multiple valves allow much greater flow at partial valve openings, when flow is dependent on total valve circumference, rather than total valve area;

Multiple valves each weigh less, allowing a higher rev ceiling without valve float;

Answer 6

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Really helps if we have some idea what motor you are talking about. That way we would have some ide if they even came with a 4 valve head.

Answer 7

In addition to what the other guys said, a smaller valve weighs less than a large one. This means less reciprocating mass, meaning the engine can rev higher without experiencing valve float.

Answer 8

Steve Y got it right... almost..



2 strokes can have valves on the exhaust.. Yamaha YVPS for example...



http://en.wikipedia.org/wiki/Two-stroke_power_valve_system