How fuel drives a car
Posted Thursday, March 10 2016 at 02:00
When you fuel your car, for some people, it is hard to understand or explain how that fuel propels the car to take you wherever you are going. However, Edgar R Batte spoke to experts and they explain how the fuel system works
The engine has been described as the heart of any car but without fuel, it cannot run. Perhaps, fuel is that blood that runs the car’s heart. Well, a driver will ignite the engine, step on the accelerator and get the car in motion but there is a whole science that happens within that split second.
Shell Fuels brand ambassador, Paul Duke Kaganzi, explains that the vehicle fuel system stores and supplies fuel to the engine.
In the engine intake system, the fuel is mixed with air delivered to the combustion system after being atomized (converted) and vaporized by the fuel injectors.
“The combustion system compresses the fuel in the engine cylinder and ignites it by spark (for petrol) or compression (for diesel) to produce energy. All fuel systems supply fuel to the combustion chamber and control the fuel air ratio,” Kaganzi explains.
Types of fuel systems
Andy Musoke, a motor technician, observes that there are two types of fuel systems; petrol and diesel.
“In the first engines is what we call the carburettor. When fuel is pumped out of the tank, it goes through a fuel filter, and carburettor and every time you step on the accelerator, the jet will squeeze fuel into the inlet manifold and then go into the required cylinder and combustion takes place,” he explains.
He adds that modern engines have a fuel injection system in which fuel is constantly pumped and then into an injector, which is electrically controlled.
It will squeeze a certain amount of fuel into the cylinders at a particular time to allow the combustion to take place.
Different fuels work
How diesel engine fuel works
Musoke says a diesel engine works through combustion ignition of the engine. “Here you have the air it draws straight into the cylinder and is compressed thus heating the air up. When it becomes hot, the diesel is squeezed and because the air is already hot, it causes combustion to take place,” he further explains.
How petro engine fuel works
In short, Musoke adds, the petrol engine has a spark plug while the diesel engine does not. The engine works in a four-stroke system. The upward and downward movements of the pistons during the combustion cycle in a four-stroke engine help to turn a crank shaft which propels the vehicle.
Technically, Musoke explains that fuel used in vehicle engines is produced from crude oil using a refinery distillation process in a fractioning tower.
Simply put, the crude oil is heated up to 400 degrees centigrade.
Disadvantages of the different fuels
“As the crude oil heats up, it distils and separates different fuels and oils at different temperatures as they are collected,” he adds. There are different fuels and oils on the market and Kaganzi says the officially recognized main grade fuels in Uganda are unleaded gasoline (ULG) also called Petrol or Automotive Gas Oil (AGO) or what is commonly known as diesel.
“International environmental protection legislation and standards binding all countries including Uganda have led to the ban or discouragement of importation of leaded petrol or high sulphur diesel. Unleaded petrol (ULG) has been around for more than a decade having replaced leaded petrol whose component chemical lead is considered harmful to the environment. Today we have low sulphur diesel on the Ugandan market,” Shell’s brand ambassador explains.
He adds that vehicles manufactured in the post 1990 and 2000 are built with emission systems which are compliant to the new global emission standards.
These vehicle emission systems are fitted with exhaust particulate breakdown or filtering components (Catalytic converters and Diesel particulate filters) designed to work with the approved fuel ULG unleaded petrol or low sulphur diesel AGO.
Kaganzi also adds that fuelling your vehicle with leaded petrol or high sulphur diesel pollutes the environment and also causes expensive damage to the vehicle emission control system.
Differentiated fuels are base fuels composed with chemical additives which are designed to improve vehicle engine performance, efficiency and protection.
The technical explanation goes to capture the fact that gasoline or petrol fuel differentiation can be achieved by a higher Research Octane Number (RON).
Octanes are a family of hydrocarbons that make up gasoline (petrol). RON is the measure of a fuel’s tendency to burn in a slower and more controlled way.
Higher RON petrol fuel reduces cylinder knock or ping and provides higher compression which delivers a better performance.
How fuel is adulterated
Andy Musoke, a motor technician, says as a mechanical engineer, he only trusts and uses products from recognised fuel stations for fear of adulterated fuel or products, which according to the dictionary, is fuel that has been made impure by adding extraneous, improper, or inferior ingredients.
The technician points to an incident where a driver was served with adulterated fuel. “The fuel was mixed with water and some other stuff which when he ignited the engine, affected the engine. I had to wash the whole engine of these impurities before refuelled at one of the recognised fuel stations,” Musoke recounts.
Shell Fuels brand ambassador, Paul Duke Kaganzi, confirms that fuel adulteration is the illegal introduction of other chemicals or liquid products such as water to a base fuel which results in the product not conforming to the recognised specifications and standards of the fuel product.
He points out that the common purpose of fuel adulteration is to increase quantity of the fuel for increased profit, adding that in Uganda and around the world, a common adulterant used is kerosene (paraffin) because it is from the same hydrocarbon product diesel and petrol is only separated during distillation.