Fuel filters, high pressure on performance

Today, engines are becoming cleaner and more powerful. This also means more is expected of your fuel filters. In this blog we take a closer look at the importance of good fuel filtration and what happens to your engine if you don't pay attention to your fuel filters.

Common rail diesel engines

One of the biggest innovations in diesel engines is the common rail system. This ensures that the diesel is fed to the injectors in a single pipe, the “rail”. In the newer common rail engines this happens under very high pressure. This pressure ensures that the diesel molecules spread more finely and you get a better air-fuel mix. This better and finer mixture burns more of the fuel in your cylinders and gives you more output with the same or even less fuel. This not only makes engines more economical, but also emits less.

In modern engines you have to deal with extremely high pressure. At idle you should think about 300 to 400 Bar. At full power this can rise to over 2600 Bar.

This high pressure also makes modern engines much more sensitive to small contamination in the fuel. Under these high pressures, small leaks in the supply and combustion can cause minimal damage that quickly lead to larger damage.

How clean is fuel?

You would expect freshly refueled diesel to be very clean. However, this is not true. There are certain standards for different phases.

Phase 0

This is the phase directly from the refinery or your diesel supplier. This diesel contains much more pollution than your engine can handle. This is also why you often place a filter on your diesel tank to do the first coarse filtration before it goes into the tank of your machine. There is an international standard for how clean this diesel is. This is the ISO-4406 standard. This standard qualifies how many particles the diesel may contain to receive the “clean fuel” label.

Phase 1

This is the first filter on your machine that filters the diesel before it goes to the filter that removes the smallest particles from the diesel. This pre-filter also removes most of the moisture from the diesel.

Phase 2

This is the phase where the very fine filtering takes place. This filter removes particles with a size of only 4 microns. This is smaller than a human blood cell. And the filters in this phase must not only stop some of the contamination, but almost all of it. If you do not have a good filter in this phase, these particles will go directly into your injectors. The diesel must meet different standards in this phase, compared to phase 0, to become ISO 4406 certified. The label in this phase is “ultra clean fuel”.

Difference between phase 0 and phase 2

To measure how clean a fuel is, three sizes of contamination are considered; 4 micron meter, 6 micron and 14 micron.

For phase 0, the ISO standard specifies the following numbers of particles per milliliter:

• 4 micron – 40000 particles/ml
• 6 microns – 10000 particles/ml
• 14 microns – 640 particles/ml

For phase 2, the ISO standard gives the following numbers:

• 4 microns – 40 particles/ml
• 6 microns – 5 particles/ml
• 14 microns – 0.64 particles/ml

This means that the diesel from the pump to the injector must be up to 1000 times cleaner to protect your engine from major internal damage.

What happens if your diesel is not clean?

Basically you can say that there are two critical points in your system. The first is before combustion and the second is after combustion. Modern engines operate under high pressure for combustion to achieve an optimal fuel-air mix. What also happens in modern engines is that, as soon as the exhaust gases leave the cylinder, afterburning takes place. A kind of second combustion round takes place in the exhaust duct. This ensures that the incompletely burned particles are still completely ignited. This results in far fewer harmful substances in the environment.

Possible damage before combustion

Here you are dealing with the pipes that carry the fuel under pressure to the injectors. Small contamination can cause minor leakage here, meaning you will not get the optimal amount of diesel in your injector.

The problem becomes bigger when you look at the atomizer itself. Injectors have become quite complex parts in the combustion process. There are two parts in the injector that are particularly affected by contamination in the fuel.

The part that ultimately releases the diesel mist is the injector needle. The diesel mist enters the cylinder from this needle. This needle is so fine that minimal damage or contamination will result in poor atomization. Poor atomization ensures that you do not have an optimal fuel-air mix. The explosion of this mix will therefore not be as homogeneous as necessary. This causes pressure differences and poorer combustion. The consequences are;

• Less power
• Your engine is not running smoothly
• More exhaust fumes
• Much more damage and higher wear of your block, cylinder head and intake valves

Possible damage after combustion

The second part that has to endure a lot in the injector is the extremely small valve that is lifted to let the fuel into the injector. This is quite a special valve, consisting of a conical disc and a metal ball of less than a millimeter in diameter. This is comparable to the size of the ball in a ballpoint pen. The tolerances in this valve are minuscule. By way of comparison, if you don't click a ballpoint pen again before you put it in your trouser pocket, it will leak under normal atmospheric pressure. In the atomizer, this valve must not leak under a pressure of 2600 Bar. You can imagine that the slightest wear and tear on this valve will cause leaks. This wear is mainly caused by the smallest particles of contamination in the fuel that passes through this valve. If wear occurs in this valve, more than necessary diesel is injected into the cylinder and at a moment of sub optimal combustion.

This leakage of diesel causes the same phenomenon as described with the injector needle. Your combustion mix is no longer homogeneous and also in the wrong ratio. This causes the same adverse effects on your engine, valves and cylinders.

How the fuel filter makes the difference

There is a big difference in the quality of fuel filters. The main difference is the filter efficiency after a number of operating hours. Even filters that meet OEM standards when new can quickly provide insufficient protection. The main reason for this is that a filter in a machine is not exposed to the same conditions as in a laboratory. A machine shakes, vibrates and moves continuously. This is why A-brands also test filters in the field.

Secondly, high-quality filters contain different materials than the cheap versions. These are often made of synthetic substances that do not break down as quickly and provide better filtration. Cellulose or fiberglass fuel filters can actually add contamination by being subject to pulverization.

High-quality filters not only stop more contamination, but can also retain it better. The filter media is often made up of different layers, each with their own function. Some filters have as many as seven different layers through which the fuel passes. The quality of a fuel filter can in principle be divided into two important properties; efficiency and capacity.

We have already talked about efficiency. Especially in practice and with more operating hours, the filter media makes a big difference. With cheaper filters, with cellulose and fiberglass filter media, up to five times as much contamination can pass through the filter towards the end of the filter's lifespan. The second property, filter capacity, is not what protects your engine better, but it does ensure a longer lifespan of your filter. The capacity of a filter means how much contamination your filter can hold before it is clogged. You simply keep a well-functioning filter for longer if the filter capacity is higher.

If you would like to view the entire range of fuel filters in our filter web shop, click on the link below:

Filter web shop – fuel filters