In recent years the method in which fuel is introduced into petrol engines has changed as technology has developed. Traditionally fuel and air are mixed before the inlet valves, the 'charge' then reaches the combustion chambers in the cylinders of the engine. However in an effort to help reduce emissions from modern engines this is no longer the case in some engines. Some modern engines are what is described as a Direct Injection (DI) engine, this is where the fuel is introduced directly into the combustion chambers, after the inlet valves of the engine and then mixes with the air to create the combustion charge.
Why is this an issue?
Direct Injection engines are suffering from very high levels of carbon deposits in the inlet manifolds, the inlet ports in the cylinder head and the inlet valves that control the flow of air into the combustion chamber.
Why does the carbonisation occur?
In engines where the fuel is introduced into the air outside of the combustion chamber, the fuel acts as a cleaning agent that washes any carbon particles into the cylinder along with the fuel/air charge, at this point the carbon is burnt as part of the combustion process and any remaining particles are exhaled from the engine through the exhaust. In a Direct Injection engine this process does not occur, the fuel is injected after the inlet system therefore the fuel does not have the chance to act as a cleaning agent to help remove the carbon deposits.
What is the effect of the carbonisation?
The carbon deposits build up over time depending on the use the vehicle undergoes. The inlet ports become covered with layer after layer of carbon deposits and start to narrow, the inlet valve stems and the back of the valves will also develop a thick layer of carbon. This effects the air flow into the engine and reduces both power output of the engine and throttle response. In the most extreme of circumstances Direct Injection engines have been seen to stop running entirely as the inlet ports and valves are so heavily carbonised that it is physically impossible for enough air to reach the combustion chambers.
Do I Have A Direct Injection Engine?
In the Volkswagen Audi Group range Direct Injection petrol engines are known as FSI or TFSI. If your VAG vehicle's engine is described as either then it is a Direct Injection engine and the issues above will occur on your vehicle.
How are the carbon deposits removed?
The air intake system of the engine must be removed in order for the cleaning to take place, as direct access to the inlet ports and valves is required. The ports are cleaned one at a time by using a tube to direct a soft blasting media at the port and valves using compressed air. The tube also acts as a connection to a vacuum system that removes the cleaning media and carbon deposits at the same time. A non-solvent base liquid neutralizer is then introduced to the cleaned area to dissolve any remaining particles and dust that remain.
What is the cost of the cleaning process?
The cost depends on several factors, firstly the complexity of removing and re-installing the air intake system and secondly the level of carbonisation that has developed in the ports and around the valves. The heavier the deposition, the more cleaning media is required to complete the process. To discuss cost further please call the workshop on 01903 718684.