Preferable number of Engine Valves

..., bigger inlet & exhaust valves are usually a good option with 'normal' 2 valve heads, one has the space that multivalve combustion chambers don't.

Some of mechanical engineers know better than me in this regard if they come to this forum topic here.

What i know is that Valves just spray the fuel in the cylinder before ignition, the more their nos the better the sequecing of spraying the fuel for ignition at the right position of piston.

More the no of valves the better is the performance of the engine and better ride it imparts to the vehicle but greater is the fuel consumption at the same time.

..factor of every day normal car type engine performance, i.e. torque production, although modern camshaft continual adjustment systems(a la VTEC) do help an otherwise torque-strangled engine produce higher figures at differing rpm.

More torque means you have more force, bhp determines the speed at which that force can be applied.

For example, my 6.1 litre V12 has only two valves per cylinder, produces 'only' 440 bhp, yet has 620 Nm of torque...

On the road that equates to staggering mid-range performance without the need for multi-valves.

Don't also forget the dimensional ratio between piston size & piston stroke, one that is 'equal' is known as being a 'square' engine, as most are today, an optimum balance between bhp & torque figures.

An under-square engine means a longer stroke in comparison to piston size & will be (generally) lower revving, less bhp, but more torque production.

An over-square engine means a shorter stroke in comparison to piston size & will be (generally) a higher revving, more bhp, but less torque production.

Each of the above engine configurations will produce very different drives, number of gear-changes as just one example.

As correctly stated valves & the number thereof per cylinder govern fuel air mix & the efficiency thereof, however they aren't the only aspects to engine performance & consequent on or off-road vehicle driving characteristics.

Torque

Check it out, DaRube, Rolls Royce, General Electric, Ford .. they all offer jet engines. Why would you want one?

which can you buy

7x or 900EX

i like 2000DX

[img_assist|nid=73057|title=.|desc=|link=none|align=left|width=|height=0]

you can also buy a jet engine with 500 000 Newton Thrust!

ill add your grade... will be 99!!! :D

thank you habibi...

~~~proud to be from where i was i shall return with~~~

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Producing More Engine Power

Using all of this information, you can begin to see that there are lots of different ways to make an engine perform better. Car manufacturers are constantly playing with all of the following variables to make an engine more powerful and/or more fuel efficient.

Increase displacement - More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger or by adding more cylinders. Twelve cylinders seems to be the practical limit.

Increase the compression ratio - Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (before the spark plug ignites it). Higher-octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high-octane gasoline -- their engines are using higher compression ratios to get more power.

Stuff more into each cylinder - If you can cram more air (and therefore fuel) into a cylinder of a given size, you can get more power from the cylinder (in the same way that you would by increasing the size of the cylinder). Turbochargers and superchargers pressurize the incoming air to effectively cram more air into a cylinder.

FABRICE COFFRINI/AFP/Getty ImagesThe turbocharger system of the Nissan GT-R.

Cool the incoming air - Compressing air raises its temperature. However, you would like to have the coolest air possible in the cylinder because the hotter the air is, the less it will expand when combustion takes place. Therefore, many turbocharged and supercharged cars have an intercooler. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder. p>

Let air come in more easily - As a piston moves down in the intake stroke, air resistance can rob power from the engine. Air resistance can be lessened dramatically by putting two intake valves in each cylinder. Some newer cars are also using polished intake manifolds to eliminate air resistance there. Bigger air filters can also improve air flow.

Let exhaust exit more easily - If air resistance makes it hard for exhaust to exit a cylinder, it robs the engine of power. Air resistance can be lessened by adding a second exhaust valve to each cylinder (a car with two intake and two exhaust valves has four valves per cylinder, which improves performance -- when you hear a car ad tell you the car has four cylinders and 16 valves, what the ad is saying is that the engine has four valves per cylinder). If the exhaust pipe is too small or the muffler has a lot of air resistance, this can cause back-pressure, which has the same effect. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system. When you hear that a car has "dual exhaust," the goal is to improve the flow of exhaust by having two exhaust pipes instead of one.

Make everything lighter - Lightweight parts help the engine perform better. Each time a piston changes direction, it uses up energy to stop the travel in one direction and start it in another. The lighter the piston, the less energy it takes.

Inject the fuel - Fuel injection allows very precise metering of fuel to each cylinder. This improves performance and fuel economy.

The wise person has long ears and a short tongue.

maxmo, very cute, indeed, shukran habibi

Well, I am not that good with engines. All I know is that when i insert my key and turn it, there is some sound generted that indicates the car is ready to move and i change the gares and accelerate...

To answer the above post, first reffer to the image:

Most engine subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine. Let's look at all of the different subsystems used in modern engines, beginning with the valve train.

The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down, as shown in Figure.

Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves, as you see in Figure. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams." See How Camshafts Work for details.

The ignition system (Figure below) produces a high-voltage electrical charge and transmits it to the spark plugs via ignition wires. The charge first flows to a distributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylinders) coming out of it. These ignition wires send the charge to each spark plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. This approach provides maximum smoothness.

if you are unable to see the animation above, click here Engine Ignition

The wise person has long ears and a short tongue.

the same happened to Newton and Leibnitz on Calculus. What's the problem? baldrick.

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Baldrick - Qatar's answer to Google ;o)

actually, Vivo, an engine needs more air (oxygen) than fuel. The ratio is roughly 1:10 (fuel to oxygen).

more valves, more power, yet needs more fuel...

plus there are more... air chargers...etc

would these stuffs implies that the engine is horrible consuming petrol?

~~~proud to be from where i was i shall return with~~~

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thanks! ... i noticed every around some few turns formula racers get a quick park for refuelling and tire changing...

but behold the valves, there are blowers to the intake manifold...

~~~proud to be from where i was i shall return with~~~

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I appreciate your comment, baldrick, but it was Vivo who asked for some advice. Good to know that somebody else is here who knows, too.

It also means more cost when things go badly wrong so just bear that in mind

just eat another pie

that isn't a twin cam jobby. Basically more valves means you can get your mixture in quicker and gases out faster.

Your general assumption is pretty much right.

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Baldrick - Qatar's answer to Google ;o)

The crucial point are the "opening" and "closing" intervalls between "fuel induction" and "exhaust". With more valves you can extend the intervall for "fuel induction" thus the combustion chamber will be filled better. Some racers use radical camshafts (with higher lobes) to increase openening and closing intervalls. Anyway: more fuel = more power. Did you know that a Formula 1 2.9 liter engine uses up to 100 liters per 100 km?