FSI engines: pros and cons of FSI engines
Auto Terms,  Blog,  Car device

FSI engines: pros and cons of FSI engines

In modern four-wheeled vehicles, those models that are equipped with a direct injection fuel system are gaining great popularity. Today, there are many different modifications.

The fsi technology is considered one of the most advanced. Let's get to know it better: what is its peculiarity and how it differs from its analog GDI?

What is FSI injection system?

This is a development that Volkswagen presented to motorists. In fact, this is a gasoline supply system that works on a similar principle to a similar Japanese modification (called gdi) that has existed for a long time. But, as representatives of the concern assure, the TS works on a different principle.

FSI engines: pros and cons of FSI engines

The engine, which has an FSI badge on the lid, is equipped with fuel injectors installed near the spark plugs - in the cylinder head itself. Gasoline is fed directly into the cavity of the working cylinder, which is why it is called "direct".

The main difference between the appeared analogue - each engineer of the company worked to eliminate the shortcomings of the Japanese system. Thanks to this, a very similar, but slightly modified vehicle appeared in the auto world, in which fuel is mixed with air directly in the cylinder chamber.

How FSI engines work

The manufacturer divided the entire system into 2 circuits. Mostly gasoline is supplied under low pressure. It reaches the high pressure fuel pump and accumulates in the rail. The high pressure pump is followed by a circuit in which high pressure is generated.

In the first circuit, a low pressure pump is installed (most often in the gas tank), a sensor that fixes the pressure in the circuit, and a fuel filter.

FSI engines: pros and cons of FSI engines

All the main elements are located after the injection pump. This mechanism maintains a constant head, which ensures stable fuel injection. The electronic control unit receives data from the low pressure sensor and activates the main fuel pump depending on the fuel consumption of the fuel rail.

The high pressure gasoline is in the rail, to which a separate injector for each cylinder is connected. Another sensor is installed in the circuit, which transmits signals to the ECU. The electronics activate the drive for the fuel rail pump, which acts as a battery.

So that the parts do not burst from the pressure, there is a special valve in the rail (if the fuel system is not equipped with a return flow, then it is in the tank itself), which relieves excessive pressure. The electronics distributes the actuation of the injectors depending on which stroke is performed in the cylinders.

The pistons of such units will have a special design that ensures the creation of vortices in the cavity. This effect allows the air to mix better with the atomized gasoline.

FSI engines: pros and cons of FSI engines

The peculiarity of this modification is that it allows:

  • Increase the power of the internal combustion engine;
  • Reduce gasoline consumption due to a more concentrated fuel supply;
  • Reduce pollution, as BTC burns more efficiently, making the catalyst better at performing its function.

High pressure fuel pump

One of the most important mechanisms of this type of fuel system is the pump, which creates a lot of pressure in the circuit. While the engine is running, this element will pump gasoline into the circuit, since it has a rigid connection to the camshaft. More details about the design features of the mechanism are described separately.

A strong pressure in the circuit is necessary for the reason that gasoline is not supplied to the intake manifold, as in mono injection or with a distributed fuel supply, but to the cylinders themselves. The principle is almost identical to how a diesel engine works.

FSI engines: pros and cons of FSI engines

In order for the portion not only to fall into the combustion chamber, but to spray, the pressure in the circuit must be much higher than the compression index. For this reason, manufacturers cannot use conventional fuel pumps, which only pressurize up to half an atmosphere.

FSI injection pump work cycles

In order for the device to work properly, providing a stable pressure, the car must be equipped with a plunger pump modification. What a plunger is and how it works is described in a separate review.

All pump operation can be divided into the following modes:

  1. Suction of gasoline. The spring-loaded plunger is lowered to open the suction valve. Gasoline comes from the low pressure circuit;
  2. Pressure build-up. The plunger finger moves up. The inlet valve closes, and due to the generated pressure, the discharge valve opens, through which gasoline flows into the rail circuit;
  3. Pressure control. In standard mode, the valve remains inactive. As soon as the fuel pressure becomes excessive, the control unit reacts to the sensor signal and activates the dump valve, which is installed near the high-pressure fuel pump (if the system has a return flow). Excess gasoline is returned to the gas tank.

Differences between FSI engines from TSI, GDI and others

So, the principle of the system is clear. How, then, does it differ from the analogous that it was called fsi? The main difference is that it uses a conventional nozzle, the atomizer of which does not create a vortex inside the chamber.

FSI engines: pros and cons of FSI engines

Also, this system uses a simpler injection pump design than that of gdi. Another feature is the non-standard shape of the piston crown. This modification provides a portioned, “layered” fuel supply. First, a small part of the gasoline is injected, and at the end of the compression stroke, the rest of the assigned portion.

FSI engines: pros and cons of FSI engines

The main "sore" of such motors, like those of similar Japanese, German and others, is that their injectors often coke. Usually, the use of additives will delay the need for costly cleaning or replacement of these parts a little, but for this reason some people refuse to buy such vehicles.

FSI car brands

Since each manufacturer gives its name to this system, ostensibly hinting that their engineers have managed to create a "problem-free" direct injection, the essence remains the same with the exception of minor design differences.

FSI motors are the brainchild of the VAG concern. For this reason, the models produced by this brand will be equipped with them. You can read about which companies are part of the concern here... In short, under the hood of VW, Skoda, Seat and Audi you can definitely find such power units.

Here is a short video review of the most common sores of one of the problem units:

The FSI engine that started it all. Problems and disadvantages of the 1.6 FSI (BAG) engine.

Questions and answers:

What are FSI and TSI? TSI is a dual-charging internal combustion engine with a stratified injection fuel system. FSI is a motor with two sequential fuel systems (low and high pressure circuit) with fuel atomization into the cylinder.

Which is the best TSI or FSI engine? The difference between these engines is only in the presence of turbocharging. A turbine engine will consume less fuel, but have more power and higher maintenance costs.

Add a comment