Fuel, Oxygen and a Spark



Fuel injection – A science in itself

You may think that an engine and its fuel injection is a simple thing, right? You simply add fuel, set it on fire, and the magic starts to happen. Hence, the wheels turn and off you go! It sounds simple enough if you oversimplify it like that. Unfortunately, we are not working with a steam engine. An apparent simple thing such as fuel injection (getting fuel into the engine) is actually a science in itself. The way this happens will have a big influence on the engine’s power production and fuel consumption. All the while, the manufacturer has to stay within the pollution limits that emissions laws demand.

 

The good old carburetor

In the distant past, the method of administering the fuel was by way of the good old carburettor. It was a purely mechanical device that you could find on top of the engine’s intake manifold. To illustrate, at explainthatstuff.com, they give the following summary of how the carburetor works. The points refer to the numbering in the picture. If you want to read more about this topic, visit them here.

 

How it works:

Working of a Carburetor - Fuel injection 1) Air flows into the top of the carburetor from the car’s air intake. It passes through a filter that cleans it of debris.

 2) When the engine starts, the choke (blue) can be set to almost block the top of the pipe. This reduces the amount of air coming in (increasing the fuel content of the mixture entering the cylinders).

 3) In the centre of the tube, the air is forced through a narrow kink called a venturi. This makes it speed up and causes its pressure to drop.

 4) The drop in air pressure creates suction on the fuel pipe (right), drawing in fuel (orange).

 5) The throttle (green) is a valve that swivels to open or close the pipe. When the throttle is open, more air and fuel flow to the cylinders. The engine then produces more power and the car goes faster.

 6) The mixture of air and fuel flows down into the cylinders.

7) A mini-fuel tank called the float-feed chamber supplies the fuel (orange).

8) As the fuel level falls, a float in the chamber falls and opens a valve at the top.

9) When the valve opens, more fuel flows in to replenish the chamber from the main gas tank. This makes the float rise and closes the valve again.

 

The carburettor atomises the liquid fuel through a system of tubes and jets. It further adds a fine fuel spray to the passing intake air to feed the engine a fuel/air mixture. This mixture must be an appropriate richness so that it can burn to the correct extent within the cylinders. Because the fuel vapour dispenses from a central place, it was difficult to carefully meter it out per cylinder. In practice, however, each cylinder didn’t always get the same amount of fuel.

 

Electronic fuel injection

When the electronic fuel injection made its appearance, the carburetor problem was resolved. The electronic fuel injection usually employs a fuel pump that feeds high-pressure fuel to injectors. There is one injector for each cylinder. Fuel metering is precise and the engine control unit (ECU) can control it individually for every cylinder. Better control and efficiency is possible when the fuel is injected directly into the cylinder via a direct-injection system. Click on the video to see an animated version of this process. Fuel-injection systems are under precise electronic control. This fact, together with catalytic converters, makes it possible that modern emission legislation can be met.

 

Optimise the ECU

So, since a computer is overseeing this entire process, it stands to reason that the ECU knows best. Should we then conclude that nothing can be done to further optimise the system’s settings? No, certainly not. In fact, standardised ECU programming errs on the side of caution and might not be optimally efficient. This is because a one-size-fits-all ECU programming for all the engines rolling off the production line leaves room for improvement. Installing a Unichip will allow you to optimise the control maps so that they work perfectly for your specific engine.

With the Unichip, we can fine-tune the air-fuel ratio. You may get very useful performance and economy gains this way. If you are not happy within three months, we will remove your Unichip and refund you. You have nothing to lose! Do not miss out on the benefits of a Unichip. Click here to contact us and have our technicians fit your Unichip today.

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