Under the bonnet of your car is the engine. Inside this engine there are many parts. One area of the engine is called the combustion chamber, and that’s where the combustion of the air/fuel mixture takes place. One of the most efficient, practical shapes of combustion chamber is the classic hemispherical form, in which the piston top forms the base of a hemisphere, with the valves inclined at 90 to each other, and the spark-plug centrally between them. This design, classic in its symmetry, gives short flame travel from the spark-plug to the piston head, and therefore good burning.

It is used on high-performance engines, such as that in the new Lamborghini Aventador and the McLaren MP4 12C, though nowadays the angle between the valves is usually less than the classic 90, as we can see in the power unit developed by Bentley Motors for their new Bentley Mulsanne. The hemispherical layout requires the use of one or two overhead camshafts – or one side camshaft associated with complicated rocker and push-rod gear – to operate the two rows of valves. Its shape assists the crossflow of gases, which enter the cylinder from one side of the engine and are exhausted from the other.

This gives room for large and free-flowing inlet tracts, arranged so that the mixture enters the chamber easily and with a swirling motion. The good gas flow resulting from the unobstructed opening of its large valve gives the hemispherical head a high volumetric efficiency.

This means it can ‘breathe deeply’, drawing in a large volume of gas for the space available, although this space is never completely filled. With efficient combustion, the hemispherical head gives a high power output.
However, the modern tendency towards larger cylinder bores and shorter piston strokes enables valves on an ordinary in line engine, without hemispherical combustion chambers, to be big enough for most normal requirements. Such valves do not need special camshafts or rocker arrangements, making the engine less costly to produce.

If you are tired of polluting the environment with a car that is not ecofriendly, consider trading it in for something that gets great gas mileage. Cars with best gas mileage come in all shapes, sizes and colors, so there is a fuel-efficient car for everyone out there. Upgrading to a gas-friendly car is a win-win situation. These cars burn less gas, so they give off much less pollution than older cars. You will also save lots of money in the long run. If you are trading in an older vehicle or a newer vehicle that is large and not efficient, you will see instant savings on your weekly gas budget. Some people spend hundreds of dollars on gas each week, and this amount can be slashed dramatically by simply switching to fuel-efficient vehicles. When the cost of everything around the world is rising, it makes sense to find savings in any place possible.