Car Engine Sizes Explained
Everyone who buys a new car will talk about its engine size as a measure of brilliance. Whilst a larger engine will generally provide more power, there is more to it than that. Instead of following the adverts and repeating engine sizes as a matter of importance, read on to understand what engine sizes can really mean to you.
What the Size Actually Means
Understanding the meaning of engine sizes requires that you know how they work. In internal combustion engines the power is created by explosions. Air and fuel are compressed together until a spark ignites this mixture. The explosion caused will push the piston away and this energy is utilised to power the vehicle. The Bore and Stroke sizes of these pistons are what tells you the engine size of a car. The Bore refers to the size of the cylinder and the Stroke refers to the distance that the piston will move within this. When this volume is multiplied by the number of cylinders and pistons, the result is the size that car adverts boast about. Your local mechanic will even be able to merely look at the pistons to calculate the size of the engine.
The size of the engine as detailed above is also known as the displacement. The amount of air which can be moved through the engine basically determines the power that it can create. There is, of course, a cost to creating more power. Fuel is also needed as well as air and a bigger engine will require more fuel to create the extra power. Leasing a car with a huge engine may be fun for a week, but the cost of fuel will make it somewhat impractical as an everyday mode of transport.
Size & Cylinders
Size is fairly obvious in terms of the fact that a bigger engine will run faster. This is because it can move more air through the engine at once. Many cars, however, have smaller engines but more cylinders. Some cars have up to 10 cylinders. A 2 litre engine with 4 cylinders will also not be as quick as a 2 litre engine with 6 cylinders. The reason for this is that engines with more cylinders have smaller parts and they can thus move at a faster rate. This means that the 6 cylinder engine, whilst being no bigger in terms of displacement than its counterpart, will go faster because the same amount of air can be moved through the engine at a faster rate. The smaller parts mean that this speed of operation can be increased, but this will once again cost more in terms of fuel.
While at this point it may seem obvious that a larger engine with more cylinders is better, this is not always the case. You also need to consider the peak performance zone of the car. Engines will have a rating along the lines of 160 HP @ 2000 RPM. What this means is that the engine will generate 160 horse power when it is running at 2000 revs per minute. Given that the average driving takes place between 1000 and 3000 RPM, this engine looks good to be utilised properly during normal driving. A better engine which has 195 HP @ 6000 RPM would, however, actually perform worse in every day driving. Failing to meet the peak performance level means that the engine power is wasted and this engine may even be running at 100 HP despite having far more to give.